1.
Psychoacoustics
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Psychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound and it can be further categorized as a branch of psychophysics. Psychoacoustics received its name from a field within psychology—i. e, recognition science—which deals with all kinds of human perceptions. It is a field of many areas, including psychology, acoustics, electronic engineering, physics, biology, physiology. These nerve pulses then travel to the brain where they are perceived, the inner ear, for example, does significant signal processing in converting sound waveforms into neural stimuli, so certain differences between waveforms may be imperceptible. Data compression techniques, such as MP3, make use of this fact, in addition, the ear has a nonlinear response to sounds of different intensity levels, this nonlinear response is called loudness. Telephone networks and audio noise reduction systems make use of this fact by nonlinearly compressing data samples before transmission, another effect of the ears nonlinear response is that sounds that are close in frequency produce phantom beat notes, or intermodulation distortion products. The expression that one hears what one wants to hear may pertain in such discussions, the human ear can nominally hear sounds in the range 20 Hz to 20,000 Hz. The upper limit tends to decrease with age, most adults are unable to hear above 16 kHz, the lowest frequency that has been identified as a musical tone is 12 Hz under ideal laboratory conditions. Tones between 4 and 16 Hz can be perceived via the sense of touch. Frequency resolution of the ear is 3.6 Hz within the octave of 1000 –2000 Hz and that is, changes in pitch larger than 3.6 Hz can be perceived in a clinical setting. However, even smaller pitch differences can be perceived through other means, for example, the interference of two pitches can often be heard as a repetitive variation in volume of the tone. This amplitude modulation occurs with a equal to the difference in frequencies of the two tones and is known as beating. The semitone scale used in Western musical notation is not a frequency scale. The intensity range of sounds is enormous. Human ear drums are sensitive to variations in the sound pressure, for this reason, sound pressure level is also measured logarithmically, with all pressures referenced to 20 µPa. The lower limit of audibility is defined as 0 dB. The upper limit is more a question of the limit where the ear will be harmed or with the potential to cause noise-induced hearing loss
2.
Acoustics
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Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of technology may be called an acoustical engineer. The application of acoustics is present in almost all aspects of society with the most obvious being the audio. Hearing is one of the most crucial means of survival in the animal world, accordingly, the science of acoustics spreads across many facets of human society—music, medicine, architecture, industrial production, warfare and more. Likewise, animal species such as songbirds and frogs use sound, art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsays Wheel of Acoustics is a well accepted overview of the fields in acoustics. The word acoustic is derived from the Greek word ἀκουστικός, meaning of or for hearing, ready to hear and that from ἀκουστός, heard, audible, which in turn derives from the verb ἀκούω, I hear. The Latin synonym is sonic, after which the term used to be a synonym for acoustics. Frequencies above and below the range are called ultrasonic and infrasonic. If, for example, a string of a length would sound particularly harmonious with a string of twice the length. In modern parlance, if a string sounds the note C when plucked, a string twice as long will sound a C an octave lower. In one system of tuning, the tones in between are then given by 16,9 for D,8,5 for E,3,2 for F,4,3 for G,6,5 for A. Aristotle understood that sound consisted of compressions and rarefactions of air which falls upon, a very good expression of the nature of wave motion. The physical understanding of acoustical processes advanced rapidly during and after the Scientific Revolution, mainly Galileo Galilei but also Marin Mersenne, independently, discovered the complete laws of vibrating strings. Experimental measurements of the speed of sound in air were carried out successfully between 1630 and 1680 by a number of investigators, prominently Mersenne, meanwhile, Newton derived the relationship for wave velocity in solids, a cornerstone of physical acoustics. The eighteenth century saw advances in acoustics as mathematicians applied the new techniques of calculus to elaborate theories of sound wave propagation. Also in the 19th century, Wheatstone, Ohm, and Henry developed the analogy between electricity and acoustics, the twentieth century saw a burgeoning of technological applications of the large body of scientific knowledge that was by then in place. The first such application was Sabine’s groundbreaking work in architectural acoustics, Underwater acoustics was used for detecting submarines in the first World War
3.
Sound
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In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a transmission medium such as air or water. In physiology and psychology, sound is the reception of such waves, humans can hear sound waves with frequencies between about 20 Hz and 20 kHz. Sound above 20 kHz is ultrasound and below 20 Hz is infrasound, other animals have different hearing ranges. Acoustics is the science that deals with the study of mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound. A scientist who works in the field of acoustics is an acoustician, an audio engineer, on the other hand, is concerned with the recording, manipulation, mixing, and reproduction of sound. Auditory sensation evoked by the oscillation described in, sound can propagate through a medium such as air, water and solids as longitudinal waves and also as a transverse wave in solids. The sound waves are generated by a source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium, as the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure, velocity, at an instant in time, the pressure, velocity, and displacement vary in space. Note that the particles of the medium do not travel with the sound wave and this is intuitively obvious for a solid, and the same is true for liquids and gases. During propagation, waves can be reflected, refracted, or attenuated by the medium, the behavior of sound propagation is generally affected by three things, A complex relationship between the density and pressure of the medium. This relationship, affected by temperature, determines the speed of sound within the medium, if the medium is moving, this movement may increase or decrease the absolute speed of the sound wave depending on the direction of the movement. For example, sound moving through wind will have its speed of propagation increased by the speed of the if the sound and wind are moving in the same direction. If the sound and wind are moving in opposite directions, the speed of the wave will be decreased by the speed of the wind. Medium viscosity determines the rate at which sound is attenuated, for many media, such as air or water, attenuation due to viscosity is negligible. When sound is moving through a medium that does not have constant physical properties, the mechanical vibrations that can be interpreted as sound can travel through all forms of matter, gases, liquids, solids, and plasmas. The matter that supports the sound is called the medium, sound cannot travel through a vacuum. Sound is transmitted through gases, plasma, and liquids as longitudinal waves and it requires a medium to propagate
4.
Reflection (physics)
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Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves, the law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar, in geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water, Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission, even hard X-rays and gamma rays can be reflected at shallow angles with special grazing mirrors. Reflection of light is either specular or diffuse depending on the nature of the interface, a mirror provides the most common model for specular light reflection, and typically consists of a glass sheet with a metallic coating where the reflection actually occurs. Reflection is enhanced in metals by suppression of wave propagation beyond their skin depths, Reflection also occurs at the surface of transparent media, such as water or glass. In the diagram, a light ray PO strikes a vertical mirror at point O, by projecting an imaginary line through point O perpendicular to the mirror, known as the normal, we can measure the angle of incidence, θi and the angle of reflection, θr. The law of reflection states that θi = θr, or in other words, in fact, reflection of light may occur whenever light travels from a medium of a given refractive index into a medium with a different refractive index. In the most general case, a fraction of the light is reflected from the interface. This is analogous to the way impedance mismatch in a circuit causes reflection of signals. Total internal reflection of light from a denser medium occurs if the angle of incidence is above the critical angle, total internal reflection is used as a means of focusing waves that cannot effectively be reflected by common means. X-ray telescopes are constructed by creating a tunnel for the waves. As the waves interact at low angle with the surface of this tunnel they are reflected toward the focus point, a conventional reflector would be useless as the X-rays would simply pass through the intended reflector. When light reflects off a material denser than the external medium, in contrast, a less dense, lower refractive index material will reflect light in phase. This is an important principle in the field of thin-film optics, specular reflection at a curved surface forms an image which may be magnified or demagnified, curved mirrors have optical power. Such mirrors may have surfaces that are spherical or parabolic, if the reflecting surface is very smooth, the reflection of light that occurs is called specular or regular reflection. The laws of reflection are as follows, The incident ray, the reflected ray, the angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal
5.
Amplitude
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The amplitude of a periodic variable is a measure of its change over a single period. There are various definitions of amplitude, which are all functions of the magnitude of the difference between the extreme values. In older texts the phase is called the amplitude. Peak-to-peak amplitude is the change between peak and trough, with appropriate circuitry, peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing the waveform on an oscilloscope. Peak-to-peak is a measurement on an oscilloscope, the peaks of the waveform being easily identified and measured against the graticule. This remains a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate. In audio system measurements, telecommunications and other areas where the measurand is a signal that swings above and below a value but is not sinusoidal. If the reference is zero, this is the absolute value of the signal, if the reference is a mean value. Semi-amplitude means half the peak-to-peak amplitude, some scientists use amplitude or peak amplitude to mean semi-amplitude, that is, half the peak-to-peak amplitude. It is the most widely used measure of orbital wobble in astronomy, the RMS of the AC waveform. For complicated waveforms, especially non-repeating signals like noise, the RMS amplitude is used because it is both unambiguous and has physical significance. For example, the power transmitted by an acoustic or electromagnetic wave or by an electrical signal is proportional to the square of the RMS amplitude. For alternating current electric power, the practice is to specify RMS values of a sinusoidal waveform. One property of root mean square voltages and currents is that they produce the same heating effect as direct current in a given resistance, the peak-to-peak value is used, for example, when choosing rectifiers for power supplies, or when estimating the maximum voltage that insulation must withstand. Some common voltmeters are calibrated for RMS amplitude, but respond to the value of a rectified waveform. Many digital voltmeters and all moving coil meters are in this category, the RMS calibration is only correct for a sine wave input since the ratio between peak, average and RMS values is dependent on waveform. If the wave shape being measured is greatly different from a sine wave, true RMS-responding meters were used in radio frequency measurements, where instruments measured the heating effect in a resistor to measure current. The advent of microprocessor controlled meters capable of calculating RMS by sampling the waveform has made true RMS measurement commonplace
6.
Echo
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In audio signal processing and acoustics, echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is proportional to the distance of the surface from the source. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room, a true echo is a single reflection of the sound source. The word echo derives from the Greek ἠχώ, itself from ἦχος, echo in the folk story of Greek is a mountain nymph whose ability to speak was cursed, only able to repeat the last words anyone spoke to her. Some animals use echo for location sensing and navigation, such as cetaceans, acoustic waves are reflected by walls or other hard surfaces, such as mountains and privacy fences. The reason of reflection may be explained as a discontinuity in the propagation medium and this can be heard when the reflection returns with sufficient magnitude and delay to be perceived distinctly. When sound, or the echo itself, is reflected multiple times from multiple surfaces, the human ear cannot distinguish echo from the original direct sound if the delay is less than 1/15 of a second. The velocity of sound in dry air is approximately 343 m/s at a temperature of 25 °C, therefore, the reflecting object must be more than 17. 2m from the sound source for echo to be perceived by a person located at the source. When a sound produces an echo in two seconds, the object is 343m away. In nature, canyon walls or rock cliffs facing water are the most common settings for hearing echoes. The strength of echo is frequently measured in dB sound pressure level relative to the transmitted wave. Echoes may be desirable or undesirable, in music performance and recording, electric echo effects have been used since the 1950s. The Echoplex is a delay effect, first made in 1959 that recreates the sound of an acoustic echo. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s and was used by most of the guitar players of the era. While Echoplexes were used heavily by guitar players, many recording studios used the Echoplex. Beginning in the 1970s, Market built the solid-state Echoplex for Maestro, in the 2000s, most echo effects units use electronic or digital circuitry to recreate the echo effect. Hamilton Mausoleum, Hamilton, South Lanarkshire, Scotland, Its high stone holds the record for the longest echo in the world, gol Gumbaz of Bijapur, India, Any whisper, clap or sound gets echoed repeatedly. The gazebo of Napier Museum in Trivandrum, Kerala, India, listen to Duck echoes and an animated demonstration of how an echo is formed
7.
Millisecond
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A millisecond is a thousandth of a second. 10 milliseconds are called a centisecond,100 milliseconds are called a decisecond. To help compare orders of magnitude of different times, this page lists times between 10−3 seconds and 100 seconds, see also times of other orders of magnitude
8.
Singing
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Singing is the act of producing musical sounds with the voice, and augments regular speech by the use of sustained tonality, rhythm, and a variety of vocal techniques. A person who sings is called a singer or vocalist, Singers perform music that can be sung with or without accompaniment by musical instruments. Singing is often done in an ensemble of musicians, such as a choir of singers or a band of instrumentalists, Singers may perform as soloists, or accompanied by anything from a single instrument up to a symphony orchestra or big band. Singing can be formal or informal, arranged or improvised and it may be done as a form of religious devotion, as a hobby, as a source of pleasure, comfort, or ritual, as part of music education, or as a profession. Excellence in singing requires time, dedication, instruction, and regular practice, if practice is done on a regular basis then the sounds can become more clear and strong. Professional singers usually build their careers around one specific genre, such as classical or rock. They typically take voice training provided by teachers or vocal coaches throughout their careers. Though these four mechanisms function independently, they are coordinated in the establishment of a vocal technique and are made to interact upon one another. During passive breathing, air is inhaled with the diaphragm while exhalation occurs without any effort, exhalation may be aided by the abdominal, internal intercostal and lower pelvis/pelvic muscles. Inhalation is aided by use of external intercostals, scalenes and sternocleidomastoid muscles, the pitch is altered with the vocal cords. With the lips closed, this is called humming, humans have vocal folds which can loosen, tighten, or change their thickness, and over which breath can be transferred at varying pressures. The shape of the chest and neck, the position of the tongue, any one of these actions results in a change in pitch, volume, timbre, or tone of the sound produced. Sound also resonates within different parts of the body and an individuals size, Singers can also learn to project sound in certain ways so that it resonates better within their vocal tract. This is known as vocal resonation, another major influence on vocal sound and production is the function of the larynx which people can manipulate in different ways to produce different sounds. These different kinds of function are described as different kinds of vocal registers. The primary method for singers to accomplish this is through the use of the Singers Formant and it has also been shown that a more powerful voice may be achieved with a fatter and fluid-like vocal fold mucosa. The more pliable the mucosa, the more efficient the transfer of energy from the airflow to the vocal folds, Vocal registration refers to the system of vocal registers within the voice. A register in the voice is a series of tones, produced in the same vibratory pattern of the vocal folds
9.
Musical instrument
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A musical instrument is an instrument created or adapted to make musical sounds. In principle, any object that produces sound can be a musical instrument—it is through purpose that the object becomes a musical instrument, the history of musical instruments dates to the beginnings of human culture. Early musical instruments may have used for ritual, such as a trumpet to signal success on the hunt. Cultures eventually developed composition and performance of melodies for entertainment, Musical instruments evolved in step with changing applications. The date and origin of the first device considered an instrument is disputed. The oldest object that some refer to as a musical instrument. Some consensus dates early flutes to about 37,000 years ago, many early musical instruments were made from animal skins, bone, wood, and other non-durable materials. Musical instruments developed independently in many populated regions of the world, however, contact among civilizations caused rapid spread and adaptation of most instruments in places far from their origin. By the Middle Ages, instruments from Mesopotamia were in maritime Southeast Asia, development in the Americas occurred at a slower pace, but cultures of North, Central, and South America shared musical instruments. By 1400, musical instrument development slowed in areas and was dominated by the Occident. Musical instrument classification is a discipline in its own right, Instruments can be classified by their effective range, their material composition, their size, etc. However, the most common method, Hornbostel-Sachs, uses the means by which they produce sound. The academic study of instruments is called organology. Once humans moved from making sounds with their bodies—for example, by using objects to create music from sounds. Primitive instruments were designed to emulate natural sounds, and their purpose was ritual rather than entertainment. The concept of melody and the pursuit of musical composition were unknown to early players of musical instruments. A player sounding a flute to signal the start of a hunt does so without thought of the notion of making music. Musical instruments are constructed in an array of styles and shapes
10.
Sound reinforcement system
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In both cases, these systems reinforce sound to make it louder or distribute it to a wider audience. Some audio engineers and others in the audio industry disagree over whether these audio systems should be called sound reinforcement systems or PA systems. Distinguishing between the two terms by technology and capability is common, while others distinguish by intended use, in some regions or markets, the distinction between the two terms is important, though the terms are considered interchangeable in many professional circles. These primary parts involve varying amounts of components to achieve the desired goal of reinforcing and clarifying the sound to the audience, performers. These signal inputs are plugged into the input jacks of a thick multicore cable, the snake then routes the signals of all of the inputs to either one or two mixing consoles. In these cases, at least two audio engineers are required, one to do the FOH Main mix and one to do the Monitor mix, once the signal arrives at a channel on the mixing console, this signal can be adjusted in many ways by the sound engineer. A signal can be equalized, compressed, or panned before being routed to an output bus. The signal may also be routed into an effects processor, such as a reverb effect, which outputs a wet version of the signal. Many electronic effects units are used in sound reinforcement systems, including digital delay, some concerts use pitch correction effects, which electronically correct any out-of-tune singing. A group of signals may be routed through a bus before being sent to the main bus to allow the engineer to control the levels of several related signals at once. A bus can often be processed just like an input channel. The mix of all the different signals and channels to the master faders on the console. Mixing consoles also have additional sends, also referred to as auxes or aux sends, on each channel so that a different mix can be created. One usage for aux sends is to create a mix of the vocal, another use of an aux send is to select varying amounts of certain channels, and then route these signals to an effects processor. A common example of the use of aux sends is to send all of the vocal signals from a rock band through a reverb effect. While reverb is usually added to vocals in the mix, it is not usually added to electric bass. The next step in the path generally depends on the size of the system in place. In smaller systems, the outputs are often sent to an additional equalizer, or directly to a power amplifier
11.
Sound recording and reproduction
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Sound recording and reproduction is an electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording, prior to the development of analog recording, there were mechanical systems for reproducing instrumental music, such as wind-up music boxes and later, in the late 19th century, player pianos. Analog sound reproduction is the process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Digital recording and reproduction converts the sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a variety of media. Whereas successive copies of an analog recording tend to degrade in quality, as noise is added. A digital audio signal must be reconverted to analog form during playback before it is amplified and connected to a loudspeaker to produce sound, long before sound was first recorded on cylinders or records, music was recorded—first by written music notation, then also by mechanical devices. Fowler, this. cylinder with raised pins on the surface remained the device to produce and reproduce music mechanically until the second half of the nineteenth century. The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine, according to Fowler, the automata were a robot band that performed. more than fifty facial and body actions during each musical selection. In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder, similar designs appeared in barrel organs, musical clocks, barrel pianos, and musical boxes. A music box is a musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth of a steel comb. They were developed from musical snuff boxes of the 18th century, some of the more complex boxes also have a tiny drum and/or bells, in addition to the metal comb. The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books, the player piano, first demonstrated in 1876, used a punched paper scroll that could store an long piece of music. The most sophisticated of the rolls were hand-played, meaning that the roll represented the actual performance of an individual. This technology to record a live performance onto a piano roll was not developed until 1904, piano rolls were in continuous mass production from 1896 to 2008. A1908 U. S. Supreme Court copyright case noted that, in 1902 alone, the use of piano rolls began to decline in the 1920s although one type is still being made today. The first device that could record actual sounds as they passed through the air was the phonautograph, the earliest known recordings of the human voice are phonautograph recordings, called phonautograms, made in 1857. They consist of sheets of paper with sound-wave-modulated white lines created by a stylus that cut through a coating of soot as the paper was passed under it
12.
Effects unit
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An effects unit or pedal is an electronic or digital device that alters how a musical instrument or other audio source sounds. In the 2010s, most effects use solid state electronics and/or computer chips, some vintage effects units from the 1930s to the 1970s and modern reissues of these effects use mechanical components as well or vacuum tubes. Musicians, audio engineers and record producers use effects units during live performances or in the studio, typically with electric guitar, electronic keyboard, while guitar effects are most frequently used with electric or electronic instruments, effects can also be used with acoustic instruments, drums and vocals. Rackmounted or audio console-integrated reverb effects are used with vocals in live sound and sound recording. Examples of common units include wah-wah pedals, fuzzboxes and reverb units. A stompbox or pedal is a metal or plastic box placed on the floor in front of the musician and connected to the instrument. Pedals are usually the least expensive format, a rackmount device mounts on a standard 19-inch equipment rack and usually contains several types of effects. Rackmount effects typically have buttons and/or knobs on the face of the chassis for controlling the effects, an effects unit is also called an effect box, effects device, effects processor or simply effects. In audio engineer parlance, a signal without effects is dry, the abbreviation F/X or FX is sometimes used. A pedal-style unit may be called a box, stompbox. When a musician has multiple effects in a rack mounted road case, Effects units are available in a variety of formats or form factors. Stompboxes are usually the smallest, least expensive, and most rugged effects units, rackmount devices are generally more expensive and offer a wider range of functions. An effects unit can consist of analog or digital circuitry or a combination of the two, during a live performance, the effect is plugged into the electrical signal path of the instrument. In the studio, the instrument or other sound-sources auxiliary output is patched into the effect, form factors are part of a studio or musicians outboard gear. Stompboxes are small plastic or metal chassis which usually lie on the floor or in a pedalboard to be operated by the users feet, pedals are often rectangle-shaped, but there are a range of other shapes. Typical simple stompboxes have a single footswitch, one to three potentiometers for controlling the effect, and a single LED that indicates if the effect is on, depending on the type of pedal, the potentiometers may control different parameters of the effect. For a chorus effect, for example, the knobs may control the depth, some pedals have two knobs stacked on top of each other, enabling the unit to provide two knobs per single knob space. An effects chain or signal chain is formed by connecting two or more stompboxes, effect chains are typically created between the guitar and the amp or between the preamplifier and the power amp
13.
Decibel
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The decibel is a logarithmic unit used to express the ratio of two values of a physical quantity. One of these values is often a reference value, in which case the decibel is used to express the level of the other value relative to this reference. When used in way, the decibel symbol is often qualified with a suffix that indicates the reference quantity that has been used or some other property of the quantity being measured. For example, dBm indicates a power of one milliwatt. There are two different scales used when expressing a ratio in decibels depending on the nature of the quantities, when expressing power quantities, the number of decibels is ten times the logarithm to base 10 of the ratio of two power quantities. That is, a change in power by a factor of 10 corresponds to a 10 dB change in level, when expressing field quantities, a change in amplitude by a factor of 10 corresponds to a 20 dB change in level. The difference in scales relates to the square law of fields in three-dimensional linear space. The decibel scales differ so that comparisons can be made between related power and field quantities when they are expressed in decibels. The definition of the decibel is based on the measurement of power in telephony of the early 20th century in the Bell System in the United States. One decibel is one tenth of one bel, named in honor of Alexander Graham Bell, however, today, the decibel is used for a wide variety of measurements in science and engineering, most prominently in acoustics, electronics, and control theory. In electronics, the gains of amplifiers, attenuation of signals, the decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. The unit for loss was originally Miles of Standard Cable, the standard telephone cable implied was a cable having uniformly distributed resistance of 88 ohms per loop mile and uniformly distributed shunt capacitance of 0.054 microfarad per mile. 1 TU was defined such that the number of TUs was ten times the logarithm of the ratio of measured power to a reference power level. The definition was conveniently chosen such that 1 TU approximated 1 MSC, in 1928, the Bell system renamed the TU into the decibel, being one tenth of a newly defined unit for the base-10 logarithm of the power ratio. It was named the bel, in honor of the telecommunications pioneer Alexander Graham Bell, the bel is seldom used, as the decibel was the proposed working unit. However, the decibel is recognized by international bodies such as the International Electrotechnical Commission. The term field quantity is deprecated by ISO 80000-1, which favors root-power, in spite of their widespread use, suffixes are not recognized by the IEC or ISO. The ISO Standard 80000-3,2006 defines the following quantities, the decibel is one-tenth of a bel,1 dB =0.1 B
14.
Wallace Clement Sabine
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Wallace Clement Sabine was an American physicist who founded the field of architectural acoustics. He graduated from Ohio State University in 1886 at the age of 18 before joining Harvard University for graduate study, Sabine was architectural acoustician of Bostons Symphony Hall, widely considered one of the two or three best concert halls in the world for its acoustics. Sabines career is the story of the birth of the field of architectural acoustics. In 1895, acoustically improving the Fogg Lecture Hall, part of the recently constructed Fogg Art Museum, was considered a task by the senior staff of the physics department at Harvard. The assignment was passed down until it landed on the shoulders of a physics professor. Although considered a popular lecturer by the students, Sabine had never received his Ph. D. Sabine tackled the problem by trying to determine what made the Fogg Lecture Hall different from other, acoustically acceptable facilities. In particular, the Sanders Theater was considered acoustically excellent, for the next several years, Sabine and a group of assistants spent each night moving materials between the two lecture halls and testing the acoustics. On some nights they would borrow hundreds of seat cushions from the Sanders Theater, once the measurements were taken and before morning arrived, everything was quickly replaced in both lecture halls, in order to be ready for classes the next day. His formula, if all units are SI, is T = V A ⋅0.25 seconds, while optimal lecture hall acoustics featured reverberation times of slightly under 1 second. Regarding the Fogg Museum lecture room, Sabine noted that a word remained audible for about 5.5 seconds. Listeners thus contended with a high degree of resonance and echo. Using what he discovered, Sabine deployed sound absorbing materials throughout the Fogg Lecture Hall to cut its reverberation time and reduce the echo effect. This accomplishment cemented Wallace Sabines career, and led to his hiring as the consultant for Bostons Symphony Hall. His acoustic design was successful and Symphony Hall is generally considered one of the best symphony halls in the world, the unit of sound absorption, the sabin, was named in his honor. F. Sanders Theatre Wallace Clement Sabine at the Mathematics Genealogy Project
15.
Stopwatch
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A stopwatch is a handheld timepiece designed to measure the amount of time elapsed from a particular time when it is activated to the time when the piece is deactivated. A large digital version of a designed for viewing at a distance. In manual timing, the clock is started and stopped by a person pressing a button, in fully automatic time, both starting and stopping are triggered automatically, by sensors. The timing functions are controlled by two buttons on the case. Pressing the top button starts the timer running, and pressing the button a second time stops it, a press of the second button then resets the stopwatch to zero. The second button is used to record split times or lap times. Pressing the split button a second time allows the watch to display of total time. Mechanical stopwatches are powered by a mainspring, which must be wound up by turning the knurled knob at the top of the watch. Digital electronic stopwatches are available which, due to their crystal oscillator timing element, are more accurate than mechanical timepieces. Because they contain a microchip, they often include date and time-of-day functions as well, stopwatches that count by 1/100 of a second are commonly mistaken as counting milliseconds, rather than centiseconds. The first digital timer used in organized sports was the Digitimer, developed by Cox Electronic Systems and it utilized a Nixie-tube readout and provided a resolution of 1/1000 second. Its first use was in ski racing, but was used by the World University Games in Moscow, Russia, the U. S. NCAA. The device is used when time periods must be measured precisely, laboratory experiments and sporting events like sprints are good examples. The stopwatch function is present as an additional function of many digital wristwatches, cell phones, portable music players. The popular newsmagazine 60 Minutes uses a ticking stopwatch as a part of its title card, chronograph Samuel Watson who made the first stopwatch
16.
Syllable
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A syllable is a unit of organization for a sequence of speech sounds. For example, the water is composed of two syllables, wa and ter. A syllable is typically made up of a nucleus with optional initial and final margins. Syllables are often considered the building blocks of words. They can influence the rhythm of a language, its prosody, its poetic meter, syllabic writing began several hundred years before the first letters. The earliest recorded syllables are on tablets written around 2800 BC in the Sumerian city of Ur and this shift from pictograms to syllables has been called the most important advance in the history of writing. A word that consists of a syllable is called a monosyllable. Syllable is an Anglo-Norman variation of Old French sillabe, from Latin syllaba, συλλαβή means what is taken together, referring to letters that are taken together to make a single sound. συλλαβή is a noun from the verb συλλαμβάνω syllambánō, a compound of the preposition σύν sýn with. The noun uses the root λαβ-, which appears in the aorist tense, the present tense stem λαμβάν- is formed by adding a nasal infix ⟨μ⟩ ⟨m⟩ before the β b and a suffix -αν -an at the end. In the International Phonetic Alphabet, the period ⟨. ⟩ marks syllable breaks, in practice, however, IPA transcription is typically divided into words by spaces, and often these spaces are also understood to be syllable breaks. When a word comes in the middle of a syllable. The liaison tie is used to join lexical words into phonological words. In the typical theory of structure, the general structure of a syllable consists of three segments. e. Nucleus and coda are grouped together as a rime and onset are only distinguished at the second level, the nucleus is usually the vowel in the middle of a syllable. The onset is the sound or sounds occurring before the nucleus, and they are sometimes collectively known as the shell. The term rime covers the nucleus plus coda, in the one-syllable English word cat, the nucleus is a, the onset c, the coda t, and the rime at. This syllable can be abstracted as a consonant-vowel-consonant syllable, abbreviated CVC, languages vary greatly in the restrictions on the sounds making up the onset, nucleus and coda of a syllable, according to what is termed a languages phonotactics
17.
Recording studio
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A recording studio is a facility for sound recording and mixing. Ideally both the recording and monitoring spaces are designed by an acoustician or audio engineer to achieve optimum acoustic properties. The engineers and producers listen to the music and the recorded tracks on monitor speakers and/or headphones. Major recording studios typically have a range of large, heavy, Isolation booths are small sound-insulated rooms with doors, designed for instrumentalists. This equipment may interfere with the recording process, Recording studios are carefully designed around the principles of room acoustics to create a set of spaces with the acoustical properties required for recording sound with precision and accuracy. This will consist of both room treatment and soundproofing to prevent sound from leaving the property. Even though sound isolation is a key goal, the musicians, singers, audio engineers and record producers still need to be able to see other, to see cue gestures. As such, the room, isolation booths, vocal booths. Some smaller studios do not have instruments, and bands and artists are expected to bring their own instruments, having musical instruments and equipment in the studio creates additional costs for a studio, as pianos have to be tuned and instruments need to be maintained. However, it makes it convenient for recording artists, as they do not have to bring in large. As well, less costly studio time is spent moving in gear, drummers bring their own snare drum, cymbals and sticks/brushes. The types and brands of equipment owned by a studio depends on the styles of music for the bands. A studio that mainly records heavy metal music will be likely to have large, powerful guitar amp heads, in contrast, a studio which mainly records country bands will likely have a selection of small, vintage combo amps. A studio that records a lot of 1970s-style funk may have an electric piano. General purpose computers have rapidly assumed a role in the recording process. A computer thus outfitted is called a Digital Audio Workstation, or DAW, other software applications include Ableton Live, Mixcraft, Cakewalk Sonar, ACID Pro, FL Studio, Adobe Audition, Auto-Tune, Audacity, and Ardour. While Apple Macintosh is used for most studio work, there is a breadth of available for Microsoft Windows. If no mixing console is used and all mixing is done using only a keyboard and mouse, the OTB is used when mixing with other hardware and not just the PC software
18.
Sound level meter
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A sound level meter is used for acoustic measurements. It is commonly a hand-held instrument with a microphone, the diaphragm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is referred to as a Sound Pressure Level Meter. This movement of the diaphragm, i. e. the sound pressure deviation, is converted into an electrical signal, a microphone is distinguishable by the voltage value produced when a known, constant sound pressure is applied. This is known as the microphone sensitivity, the instrument needs to know the sensitivity of the particular microphone being used. Using this information, the instrument is able to convert the electrical signal back to a sound pressure. Sound level meters are used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental. The current international standard that specifies sound level meter functionality and performances from is the IEC 61672-1,2013, however, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. Specific loudness is a nonlinearity that depends on level and also frequency. Svantek, Cirrus Research plc, Casella, 3M, Brüel & Kjær, the IEC 61672-1 specifies three kinds of sound measuring instruments. They are the sound level meter, the integrating-averaging sound level meter. Three of these time-weightings have been standardised, S originally called Slow, F originally called Fast. Their names were changed in the 1980s to be the same in any language, i-time-weighting is no longer in the body of the standard because it has little real correlation with the impulsive character of noise events. The output of the RMS circuit is linear in voltage and is passed through a circuit to give a readout linear in decibels. This is 20 times the base 10 logarithm of the ratio of a given sound pressure to the reference sound pressure. Root-mean-square sound pressure being obtained with a standard frequency weighting and standard time weighting, the reference pressure is set by International agreement to be 20 micropascals for airborne sound. It follows that the decibel is in a not a unit, it is simply a dimensionless ratio—in this case the ratio of two pressures. However, because sound was described in decibels, the exposure is most often described in terms of sound exposure level
19.
Blank (cartridge)
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A blank is a type of cartridge for a firearm that contains gunpowder but no bullet or shot. Blanks use paper or plastic wadding to seal gunpowder into the cartridge, when fired, the blank makes a flash and an explosive sound, the wadding is propelled from the barrel of the gun, and the firearms action cycles. Blanks are often used for simulation, training, for signaling, blank cartridges differ from dummy cartridges, which are used for training or function testing firearms, these contain no primer or gunpowder, and are inert. Specialized blank cartridges are used for their propellant force in fields as varied as construction, shooting sports. In the case of non-crimped blanks, it serves to pulverise the plug to prevent it leaving as a projectile. For movie use, specially designed blank-firing firearms are often used, 5-in-1 blanks are specifically made for theatrical use and are commonly used in real firearms for dramatic effect. 5-in-1 blanks can function in a variety of different calibers, hence the name, special blank cartridges are also used when the explosive power of a cartridge is needed, but a projectile is not. Blank cartridges were used for launching tear-gas or rifle grenades. Larger blanks are used for line launching guns, such as the line launching kit for the Mossberg 500 shotgun. Some forms of fast draw competitions use special blanks that are loaded with a layer of slow burning rifle powder on top of a layer of faster-burning pistol powder. The pistol powder ignites the slower burning powder, and fires it out the barrel much like a shotgun shell. The burning powder only travels a few yards before it completely combusts, wax bullets are also commonly used for competitions and training where a non-lethal projectile is required. This tradition dates back to before cartridge arms, when a muzzle loading musket would be loaded without a ball, the appearance of a blank cartridge can give a false sense of safety. Blank cartridges frequently contain a paper, wood or plastic called a wad which seals the powder in the case. This wad can cause severe penetrating wounds at close range and bruising at medium ranges, there is also muzzle blast – a cloud of hot, expanding gas expelled at extremely high velocity from the muzzle of the firearm. This high velocity gas can inflict severe injury at close ranges, in addition, if there is any small debris lodged inside the barrel it will be expelled at a velocity similar to that of a bullet, with the ability to inflict a severe or lethal wound. Furthermore, the loud noise of blanks being fired can damage the hearing of people in the immediate area. Actors in particular are at risk of injury from blank cartridges used on movie sets
20.
Colors of noise
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In audio engineering, electronics, physics, and many other fields, the color of noise refers to the power spectrum of a noise signal. Different colors of noise have different properties, for example, as audio signals they will sound different to human ears. Therefore, each application typically requires noise of a specific color and this sense of color for noise signals is similar to the concept of timbre in music, however the latter is almost always used for sound, and may consider very detailed features of the spectrum. The practice of naming kinds of noise after colors started with white noise and that name was given by analogy with white light, which was assumed to have such a flat power spectrum over the visible range. Other color names, like pink, red, and blue were then given to noise with other spectral profiles, some of those names have standard definitions in certain disciplines, while others are very informal and poorly defined. Many of these definitions assume a signal with components at all frequencies, with a spectral density per unit of bandwidth proportional to 1/f β. For instance, the density of white noise is flat, while flicker or pink noise has β =1. Various noise models are employed in analysis, many of which fall under the above categories, AR noise or autoregressive noise is such a model, and generates simple examples of the above noise types, and more. The Federal Standard 1037C Telecommunications Glossary defines white, pink, blue and that is, if the sound wave pattern of blue noise were translated into light waves, the resulting light would be blue, and so on. White noise is a signal, named by analogy to white light, in other words, the signal has equal power in any band of a given bandwidth when the bandwidth is measured in Hz. In this case a white noise spectrum that is sampled in the logarithm of frequency will slope upwards at higher frequencies rather than being flat. The frequency spectrum of noise is linear in logarithmic space. This means that pink noise would have power in the frequency range from 40 to 60 Hz as in the band from 4000 to 6000 Hz. The spectral power density, compared with white noise, decreases by 3 dB per octave, for this reason, pink noise is often called 1/f noise. In areas where terminology is used loosely, red noise may refer to any system where power density decreases with increasing frequency, Brownian noise can be generated with temporal integration of White noise. Brown noise is not named for a spectrum that suggests the colour brown, rather. Red noise describes the shape of the spectrum, with pink being between red and white. Also known as random walk or drunkards walk, blue noise is also called azure noise
21.
Pink noise
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Pink noise or 1⁄f noise is a signal or process with a frequency spectrum such that the power spectral density is inversely proportional to the frequency of the signal. In pink noise, each carries a equal amount of noise energy. The name arises from the appearance of visible light with this power spectrum. These pink-like noises occur widely in nature and are a source of considerable interest in many fields, the distinction between the noises with α near 1 and those with a broad range of α approximately corresponds to a much more basic distinction. The former generally come from systems in quasi-equilibrium, as discussed below. The latter generally correspond to a range of non-equilibrium driven dynamical systems. The term flicker noise is used to refer to pink noise. There is equal energy in all octaves of frequency, in terms of power at a constant bandwidth, pink noise falls off at 3 dB per octave. At high enough frequencies pink noise is never dominant, however, humans still differentiate between white noise and pink noise with ease. Systems that do not have a response can be equalized by creating an inverse filter using a graphic equalizer. Because pink noise has a tendency to occur in physical systems. Pink noise can be processed, filtered, and/or effects can be added to produce desired sounds, various crest factors of pink noise can be used in simulations of various levels of dynamic range compression in music signals. On some digital pink-noise generators the crest factor can be specified, the power spectrum of pink noise is 1/f only for one-dimensional signals. For two-dimensional signals the power spectrum is reciprocal to f 2 In general, in an n-dimensional system, for higher-dimensional signals it is still true that each octave carries an equal amount of noise power. The frequency spectrum of two-dimensional signals, for instance, is also two-dimensional, in the past quarter century, pink noise has been discovered in the statistical fluctuations of an extraordinarily diverse number of physical and biological systems. Examples of its occurrence include fluctuations in tide and river heights, quasar light emissions, heart beat, firings of single neurons, an accessible introduction to the significance of pink noise is one given by Martin Gardner in his Scientific American column Mathematical Games. In this column, Gardner asked for the sense in which music imitates nature, sounds in nature are not musical in that they tend to be either too repetitive or too chaotic. The answer to question was given in a statistical sense by Voss and Clarke
22.
White noise
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In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used, with this or similar meanings, in scientific and technical disciplines, including physics, acoustic engineering, telecommunications, statistical forecasting. White noise refers to a model for signals and signal sources. Depending on the context, one may require that the samples be independent and have identical probability distribution. In particular, if each sample has a distribution with zero mean. The samples of a noise signal may be sequential in time. The concept can be defined also for signals spread over more complicated domains, an infinite-bandwidth white noise signal is a purely theoretical construction. The bandwidth of noise is limited in practice by the mechanism of noise generation, by the transmission medium. Thus, a signal is considered white noise if it is observed to have a flat spectrum over the range of frequencies that is relevant to the context. For an audio signal, for example, the relevant range is the band of sound frequencies. Such a signal is heard as a sound, resembling the /sh/ sound in ash. In music and acoustics, the white noise may be used for any signal that has a similar hissing sound. White noise draws its name from white light, although light that appears white generally does not have a spectral power density over the visible band. The term white noise is used in the context of phylogenetically based statistical methods to refer to a lack of phylogenetic pattern in comparative data. It is sometimes used in non technical contexts, in the sense of random talk without meaningful contents. Being uncorrelated in time does not restrict the values a signal can take, any distribution of values is possible. Even a binary signal which can take on the values 1 or –1 will be white if the sequence is statistically uncorrelated. Noise having a distribution, such as a normal distribution
23.
Fourier transform
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The Fourier transform decomposes a function of time into the frequencies that make it up, in a way similar to how a musical chord can be expressed as the frequencies of its constituent notes. The Fourier transform is called the frequency domain representation of the original signal, the term Fourier transform refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of time. The Fourier transform is not limited to functions of time, but in order to have a unified language, linear operations performed in one domain have corresponding operations in the other domain, which are sometimes easier to perform. The operation of differentiation in the domain corresponds to multiplication by the frequency. Also, convolution in the domain corresponds to ordinary multiplication in the frequency domain. Concretely, this means that any linear time-invariant system, such as a filter applied to a signal, after performing the desired operations, transformation of the result can be made back to the time domain. Functions that are localized in the domain have Fourier transforms that are spread out across the frequency domain and vice versa. The Fourier transform of a Gaussian function is another Gaussian function, Joseph Fourier introduced the transform in his study of heat transfer, where Gaussian functions appear as solutions of the heat equation. The Fourier transform can also be generalized to functions of variables on Euclidean space. In general, functions to which Fourier methods are applicable are complex-valued, the latter is routinely employed to handle periodic functions. The fast Fourier transform is an algorithm for computing the DFT, the Fourier transform of the function f is traditionally denoted by adding a circumflex, f ^. There are several conventions for defining the Fourier transform of an integrable function f, ℝ → ℂ. Here we will use the definition, f ^ = ∫ − ∞ ∞ f e −2 π i x ξ d x. When the independent variable x represents time, the transform variable ξ represents frequency. Under suitable conditions, f is determined by f ^ via the inverse transform, f = ∫ − ∞ ∞ f ^ e 2 π i ξ x d ξ, the functions f and f ^ often are referred to as a Fourier integral pair or Fourier transform pair. For other common conventions and notations, including using the angular frequency ω instead of the frequency ξ, see Other conventions, the Fourier transform on Euclidean space is treated separately, in which the variable x often represents position and ξ momentum. Many other characterizations of the Fourier transform exist, for example, one uses the Stone–von Neumann theorem, the Fourier transform is the unique unitary intertwiner for the symplectic and Euclidean Schrödinger representations of the Heisenberg group. In 1822, Joseph Fourier showed that some functions could be written as an sum of harmonics
24.
Manfred R. Schroeder
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Manfred Robert Schroeder was a German physicist, most known for his contributions to acoustics and computer graphics. He wrote three books and published over 150 articles in his field, born in Ahlen, he studied at the University of Göttingen, earning a vordiplom in mathematics and Dr. rer. nat. in physics. His thesis showed how small regular cavities in concert halls cause unfortunate resonances and he joined the technical staff at Bell Labs in New Jersey researching speech and graphics, securing forty-five patents. With Bishnu Atal he was a promotor of linear predictive coding, still affiliated with Bell, he rejoined University of Göttingen as Universitätsprofessor Physik becoming professor emeritus. With B. S. Atal he developed code excited linear prediction, with Ning Xiang he was a promoter of a synchronous dual channel measurement method using reciprocal maximum-length sequences. He led a study of 22 concert halls worldwide, leading to a comparison method requiring no travel. He was a professor at University of Tokyo. Number Theory in Science and Communication, With Applications in Cryptography, Physics, Biology, Digital Information, fractals, Chaos, Power Laws, Minutes from an Infinite Paradise Computer speech recognition, compression, synthesis. With H. Quast and H. W. fellow of the Acoustical Society of America IEEE Fellow, Fellow of the American Academy of Arts and Sciences. ISCA Medal for Scientific Achievement from the International Speech Communication Association, technology Award from the German Eduard Rhein Foundation
25.
Volume
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Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance or shape occupies or contains. Volume is often quantified numerically using the SI derived unit, the cubic metre, three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straight-edged, Volumes of a complicated shape can be calculated by integral calculus if a formula exists for the shapes boundary. Where a variance in shape and volume occurs, such as those that exist between different human beings, these can be calculated using techniques such as the Body Volume Index. One-dimensional figures and two-dimensional shapes are assigned zero volume in the three-dimensional space, the volume of a solid can be determined by fluid displacement. Displacement of liquid can also be used to determine the volume of a gas, the combined volume of two substances is usually greater than the volume of one of the substances. However, sometimes one substance dissolves in the other and the volume is not additive. In differential geometry, volume is expressed by means of the volume form, in thermodynamics, volume is a fundamental parameter, and is a conjugate variable to pressure. Any unit of length gives a unit of volume, the volume of a cube whose sides have the given length. For example, a cubic centimetre is the volume of a cube whose sides are one centimetre in length, in the International System of Units, the standard unit of volume is the cubic metre. The metric system also includes the litre as a unit of volume, thus 1 litre =3 =1000 cubic centimetres =0.001 cubic metres, so 1 cubic metre =1000 litres. Small amounts of liquid are often measured in millilitres, where 1 millilitre =0.001 litres =1 cubic centimetre. Capacity is defined by the Oxford English Dictionary as the applied to the content of a vessel, and to liquids, grain, or the like. Capacity is not identical in meaning to volume, though closely related, Units of capacity are the SI litre and its derived units, and Imperial units such as gill, pint, gallon, and others. Units of volume are the cubes of units of length, in SI the units of volume and capacity are closely related, one litre is exactly 1 cubic decimetre, the capacity of a cube with a 10 cm side. In other systems the conversion is not trivial, the capacity of a fuel tank is rarely stated in cubic feet, for example. The density of an object is defined as the ratio of the mass to the volume, the inverse of density is specific volume which is defined as volume divided by mass. Specific volume is an important in thermodynamics where the volume of a working fluid is often an important parameter of a system being studied
26.
Second
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The second is the base unit of time in the International System of Units. It is qualitatively defined as the division of the hour by sixty. SI definition of second is the duration of 9192631770 periods of the corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Seconds may be measured using a mechanical, electrical or an atomic clock, SI prefixes are combined with the word second to denote subdivisions of the second, e. g. the millisecond, the microsecond, and the nanosecond. Though SI prefixes may also be used to form multiples of the such as kilosecond. The second is also the unit of time in other systems of measurement, the centimetre–gram–second, metre–kilogram–second, metre–tonne–second. Absolute zero implies no movement, and therefore zero external radiation effects, the second thus defined is consistent with the ephemeris second, which was based on astronomical measurements. The realization of the second is described briefly in a special publication from the National Institute of Standards and Technology. 1 international second is equal to, 1⁄60 minute 1⁄3,600 hour 1⁄86,400 day 1⁄31,557,600 Julian year 1⁄, more generally, = 1⁄, the Hellenistic astronomers Hipparchus and Ptolemy subdivided the day into sixty parts. They also used an hour, simple fractions of an hour. No sexagesimal unit of the day was used as an independent unit of time. The modern second is subdivided using decimals - although the third remains in some languages. The earliest clocks to display seconds appeared during the last half of the 16th century, the second became accurately measurable with the development of mechanical clocks keeping mean time, as opposed to the apparent time displayed by sundials. The earliest spring-driven timepiece with a hand which marked seconds is an unsigned clock depicting Orpheus in the Fremersdorf collection. During the 3rd quarter of the 16th century, Taqi al-Din built a clock with marks every 1/5 minute, in 1579, Jost Bürgi built a clock for William of Hesse that marked seconds. In 1581, Tycho Brahe redesigned clocks that displayed minutes at his observatory so they also displayed seconds, however, they were not yet accurate enough for seconds. In 1587, Tycho complained that his four clocks disagreed by plus or minus four seconds, in 1670, London clockmaker William Clement added this seconds pendulum to the original pendulum clock of Christiaan Huygens. From 1670 to 1680, Clement made many improvements to his clock and this clock used an anchor escapement mechanism with a seconds pendulum to display seconds in a small subdial
27.
Echo chamber
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An echo chamber is a hollow enclosure used to produce reverberated sounds, usually for recording purposes. Nowadays effects units are widely used to create such effects. In music, the use of echo and reverberation effects has taken many forms. Medieval and Renaissance sacred music relied heavily on the composers extensive understanding and use of the natural reverberation and echoes inside churches. This early acoustical knowledge informed the design of houses and concert halls in the 17th, 18th and 19th centuries. Architects designed these to create internal reflections that would enhance and project sound from the stage in the days before electrical amplification, until the 1950s echo and reverberation were typically created by a combination of electrical and physical methods. The basic purpose of such chambers is to add colour and depth to the original sound, the development of artificial echo/reverberation chambers was important for sound recording because of the limitations of early recording systems. Except in the case of live performances, most commercial recordings were made in specially constructed studios. These rooms were both heavily insulated to exclude external noises and internally somewhat anechoic—that is, they were designed not to any internal echoes or sound reverberation. Consequently, record producers and engineers came up with an effective method of adding artificial echo. Producing echo and reverberation in this form of chamber is simple. A signal from the studio mixing desk—such as a voice or instrument—is fed to a large high-fidelity loudspeaker located at one end of the chamber. One or more microphones are placed along the length of the room, the farther away from the loudspeaker, the more echo and reverberation the microphone picks up and the louder the reverberation becomes in relation to the source. The signal from the line is then fed back to the mixing desk. An example of this effect can be heard on the 1978 David Bowie song Heroes. Visconti placed three microphones at intervals along the length of the hall, one close to Bowie, one halfway down the hall. The original echo chamber at EMIs Abbey Road Studios was improved by the late Clive Robinson and his construction and engineering team perfected the echo booth at Abbey Road Studios in London. Buildings such as churches, church halls and ballrooms have often chosen as recording sites for classical and other music because of their rich, natural echo
28.
Loudspeaker
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A loudspeaker is an electroacoustic transducer, which converts an electrical audio signal into a corresponding sound. The most widely used type of speaker in the 2010s is the speaker, invented in 1925 by Edward W. Kellogg. The dynamic speaker operates on the basic principle as a dynamic microphone. Besides this most common method, there are several technologies that can be used to convert an electrical signal into sound. The sound source must be amplified or strengthened with a power amplifier before the signal is sent to the speaker. Speakers are typically housed in an enclosure or speaker cabinet which is often a rectangular or square box made of wood or sometimes plastic. The enclosures materials and design play an important role in the quality of the sound, where high fidelity reproduction of sound is required, multiple loudspeaker transducers are often mounted in the same enclosure, each reproducing a part of the audible frequency range. In this case the individual speakers are referred to as drivers, drivers made for reproducing high audio frequencies are called tweeters, those for middle frequencies are called mid-range drivers, and those for low frequencies are called woofers. Smaller loudspeakers are found in such as radios, televisions, portable audio players, computers. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, the term loudspeaker may refer to individual transducers or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a range of frequencies with even coverage, most loudspeaker systems employ more than one driver. Individual drivers are used to different frequency ranges. The drivers are named subwoofers, woofers, mid-range speakers, tweeters, the terms for different speaker drivers differ, depending on the application. In two-way systems there is no mid-range driver, so the task of reproducing the mid-range sounds falls upon the woofer and tweeter, home stereos use the designation tweeter for the high frequency driver, while professional concert systems may designate them as HF or highs. When multiple drivers are used in a system, a network, called a crossover. Loudspeaker driver of the type pictured are termed dynamic to distinguish them from earlier drivers, or speakers using piezoelectric or electrostatic systems, or any of several other sorts. Johann Philipp Reis installed an electric loudspeaker in his telephone in 1861, it was capable of reproducing clear tones, alexander Graham Bell patented his first electric loudspeaker as part of his telephone in 1876, which was followed in 1877 by an improved version from Ernst Siemens. In 1898, Horace Short patented a design for a loudspeaker driven by compressed air, he sold the rights to Charles Parsons
29.
Microphone
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A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal. Several different types of microphone are in use, which employ different methods to convert the air pressure variations of a wave to an electrical signal. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced, in order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones, some of the first examples, from fifth century BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheatres. In 1665, the English physicist Robert Hooke was the first to experiment with an other than air with the invention of the lovers telephone made of stretched wire with a cup attached at each end. German inventor Johann Philipp Reis designed an early sound transmitter that used a strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the transmitter design in Scottish-American Alexander Graham Bells telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a poor sound quality. The first microphone that enabled proper voice telephony was the carbon microphone and this was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, the carbon microphone is the direct prototype of todays microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886 and this microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910. In 1916, E. C. Wente of Western Electric developed the next breakthrough with the first condenser microphone, in 1923, the first practical moving coil microphone was built. The Marconi Skykes or magnetophon, developed by Captain H. J. Round, was the standard for BBC studios in London and this was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the microphone was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson. Over the years these microphones were developed by companies, most notably RCA that made large advancements in pattern control. With television and film technology booming there was demand for high fidelity microphones, electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. During the second half of 20th century development advanced quickly with the Shure Brothers bringing out the SM58, digital was pioneered by Milab in 1999 with the DM-1001. The latest research developments include the use of optics, lasers and interferometers
30.
Transducer
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A transducer is a device that converts one form of energy to another. Usually a transducer converts a signal in one form of energy to a signal in another, Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities. The process of converting one form of energy to another is known as transduction, passive sensors require an external power source to operate, which is called an excitation signal. The signal is modulated by the sensor to produce an output signal, active sensors generate electric signals in response to an external stimulus without the need of an additional energy source. Such examples are a photodiode, and a sensor, thermocouple. A sensor is a device that receives and responds to a signal or stimulus, transducer is the other term that is sometimes interchangeably used instead of the term sensor, although there are subtle differences. A transducer is a term that can be used for the definition of many such as sensors, actuators. An actuator is a device that is responsible for moving or controlling a mechanism or system and it is operated by a source of energy, which can be mechanical force, electrical current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a system acts upon an environment. The control system can be simple, software-based, a human, bidirectional transducers convert physical phenomena to electrical signals and also convert electrical signals into physical phenomena. Likewise, DC electric motors may be used to generate electrical power if the shaft is turned by an external torque. Radio transmitters converts electrical signals to electromagnetic transmissions, horn analyzer List of sensors Tactile sensor Agarwal, Anant. Foundations of Analog and Digital Electronic Circuits. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology,2005, p.43. Introduction to Closed Loop Hall Effect Current Transducers Federal Standard 1037C, August 7,1996, transducer A sound transducer with a flat flexible diaphragm working with bending waves
31.
Sheet metal
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Sheet metal is metal formed by an industrial process into thin, flat pieces. It is one of the forms used in metalworking and it can be cut. Countless everyday objects are fabricated from sheet metal, thicknesses can vary significantly, extremely thin thicknesses are considered foil or leaf, and pieces thicker than 6 mm are considered plate. Sheet metal is available in flat pieces or coiled strips, the coils are formed by running a continuous sheet of metal through a roll slitter. The thickness of metal is in the USA commonly specified by a traditional. The larger the number, the thinner the metal. Commonly used steel sheet metal ranges from 30 gauge to about 7 gauge, in the rest of the world, the sheet metal thickness is given in millimeters. There are many different metals that can be made into metal, such as aluminium, brass, copper, steel, tin, nickel. Sheet metal of iron and other materials with high permeability, also known as laminated steel cores, has applications in transformers. Historically, an important use of metal was in plate armor worn by cavalry. Sheet metal workers are known as tin bashers, a name derived from the hammering of panel seams when installing tin roofs. Grade 304 is the most common of the three grades and it offers good corrosion resistance while maintaining formability and weldability. Available finishes are #2B, #3, and #4, grade 303 is not available in sheet form. Grade 316 possesses more corrosion resistance and strength at elevated temperatures than 304 and it is commonly used for pumps, valves, chemical equipment, and marine applications. Available finishes are #2B, #3, and #4, grade 410 is a heat treatable stainless steel, but it has a lower corrosion resistance than the other grades. It is commonly used in cutlery, the only available finish is dull. Grade 430 is popular grade, low cost alternative to series 300s grades, used when high corrosion resistance is not a primary criteria. Common grade for appliance products, often with a brushed finish, aluminum is also a popular metal used in sheet metal due to its flexibility, wide range of options, cost effectiveness, and other properties
32.
Contact microphone
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A contact microphone, also known as a pickup or a piezo, is a form of microphone that senses audio vibrations through contact with solid objects. Unlike normal air microphones, contact mics are almost completely insensitive to air vibrations, often used as acoustic leakage probes, they also enjoy wide usage by noise music artists experimenting with sound. Contact microphones based on materials are passive and high-impedance, which can make them sound tinny without a matching preamp. The most commonly available contact microphone element is made of a piezoelectric ceramic round glued to a thin brass or alloy metal disc. This center disc is positive while the disc is negative. If this silver disc is cracked or scorched, the piezo will no longer function at full sensitivity, more recently, flexible PVDF fluoropolymer piezo film has been developed in tabs, strips, cables, and large sheets. Piezo cable is often used buried under roads as traffic sensors
33.
Elektro-Mess-Technik
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The company was founded by Wilhelm Franz. Wilhelm Franz, born in Bremen in 1913, founded his first firm, two years later Wilhelm’s brother, Walter, joined the company. The Allied bombing air raids over Berlin intensified in 1943 and Franz moved to Schuttertal, then, after 1945, to Lahr, the logo of an arrowhead was chosen as a symbol of the passage of an electric signal in an electronic circuitry. After the war Franz, in co-operation with the ‘Rundfunktechnisches Institut’, directed by Dr. Ing. Walter Kuhl, introduced in 1951, the 927 is an impressive machine, outstanding in size and performance. Its enormous main platter was necessary to play 16” acetate records, additionally it could play the 33 1⁄3 rpm 12” Long-Playing records and 7”45 rpm discs. The Danish firm Ortofon provided the tonearm for the 927 and the first magnetic pickup officially installed by EMT on their turntables, the 12” disc gradually became the standard source of pre-recorded music and the 16” record disappeared. The ‘930’ is a machine as well, that maintains all the functional characteristics of the larger brother in a more compact package. Its very sturdy cast-metal frame, ‘Kunststoff’ main board and idler-wheel drive to the rim of its heavy platter gives it peerless sonic qualities. The drive system, start/stop system, brake and speed control are exactly as on the 927, the preamplifier of the monophonic 930 was the tube ‘139’. In 1957 it began the production of machine that would become a real ‘best-seller’. Developed, like the ‘R80’ turntable, in co-operation with the ‘Rundfunktechnisches Institut’, in that same year, Studer and EMT began to cooperate officially in the professional sound sector, the German firm becoming a distributor for many world markets of the excellent Swiss equipment. The success of this company, directed by Eugene Sporri since 1962, is driven by the Studer C37, in the same period, the German firm printed the first issue of its fabled ‘bulletin’, named ‘EMT-Kurier’ in the German edition, ‘EMT-Courier’ in the English one. 46 issues were printed, they are amongst the more treasured printed items for the EMT collector, in the following years, while Studer/Revox developed their own distribution network, Franz slowly tightened its relations with Thorens until, in 1966, he bought a majority stake in the firm. The production of their excellent turntable was then relocated from Wettingen to Lahr’s Gerätewerk and it was also this close co-operation that carried, in 1969, to the birth of the first EMT tonearm, the fabulous ‘929’, loosely based on Thorens 9” ‘TP-14’/BTP-12S’ arms. The 10” long 929 replaced the Ortofon ‘RF229/RMA229’, while the version of the 929. In 1968, to try to fight the tide of Japanese turntables, it was decided to try to ‘diversify’ the range of professional turntables. EMT modified the electronics, fitted their own RIAA-curve compensating circuitry and preamplifier, stiffened the suspension of the main chassis. The 928, that used the new 929 tonearm, was the last EMT turntable to appear under the management of Wilhelm Franz, who died in date April 10,1971, at the age of 58 years
34.
The Beatles
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The Beatles were an English rock band, formed in Liverpool in 1960. With members John Lennon, Paul McCartney, George Harrison and Ringo Starr, the Beatles built their reputation playing clubs in Liverpool and Hamburg over a three-year period from 1960, with Stuart Sutcliffe initially serving as bass player. The core of Lennon, McCartney and Harrison went through a succession of drummers, including Pete Best, before asking Starr to join them. They acquired the nickname the Fab Four as Beatlemania grew in Britain the next year, from 1965 onwards, the Beatles produced increasingly innovative recordings, including the albums Rubber Soul, Revolver, Sgt. Peppers Lonely Hearts Club Band, The Beatles and Abbey Road, after their break-up in 1970, they each enjoyed successful musical careers of varying lengths. McCartney and Starr, the members, remain musically active. Lennon was shot and killed in December 1980, and Harrison died of cancer in November 2001. The Beatles are the band in history, with estimated sales of over 600 million records worldwide. They have had more number-one albums on the British charts and sold more singles in the UK than any other act, according to the RIAA, the Beatles are also the best-selling music artists in the United States, with 178 million certified units. In 2008, the group topped Billboard magazines list of the all-time most successful Hot 100 artists, as of 2016 and they have received ten Grammy Awards, an Academy Award for Best Original Song Score and fifteen Ivor Novello Awards. The group was inducted into the Rock and Roll Hall of Fame in 1988 and they were also collectively included in Time magazines compilation of the twentieth centurys 100 most influential people. In March 1957, John Lennon, then aged sixteen, formed a group with several friends from Quarry Bank school. They briefly called themselves the Blackjacks, before changing their name to the Quarrymen after discovering that a local group was already using the other name. Fifteen-year-old Paul McCartney joined as a rhythm guitarist shortly after he, in February 1958, McCartney invited his friend George Harrison to watch the band. The fourteen-year-old auditioned for Lennon, impressing him with his playing, after a month of Harrisons persistence, they enlisted him as their lead guitarist. By January 1959, Lennons Quarry Bank friends had left the group, the three guitarists, billing themselves at least three times as Johnny and the Moondogs, were playing rock and roll whenever they could find a drummer. They used the name until May, when they became the Silver Beetles, before undertaking a tour of Scotland as the backing group for pop singer. By early July, they had changed their name to the Silver Beatles, allan Williams, the Beatles unofficial manager, arranged a residency for them in Hamburg, but lacking a full-time drummer they auditioned and hired Pete Best in mid-August 1960
35.
Pink Floyd
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Pink Floyd were an English rock band formed in London. They achieved international acclaim with their progressive and psychedelic music, Pink Floyd were founded in 1965 by students Syd Barrett on guitar and lead vocals, Nick Mason on drums, Roger Waters on bass and vocals, and Richard Wright on keyboards and vocals. Guitarist David Gilmour joined in December 1967, Barrett left in April 1968 due to deteriorating mental health. Waters became the primary lyricist and conceptual leader, devising the concepts behind their albums The Dark Side of the Moon, Wish You Were Here, Animals, The Wall. The Dark Side of the Moon and The Wall became two of the albums of all time. Following creative tensions, Wright left Pink Floyd in 1979, followed by Waters in 1985, Gilmour and Mason continued as Pink Floyd, Wright rejoined them as a session musician and, later, a band member. The three produced two more albums—A Momentary Lapse of Reason and The Division Bell —and toured through 1994, Barrett died in 2006, and Wright in 2008. The final Pink Floyd studio album, The Endless River, was recorded without Waters, Pink Floyd were inducted into the American Rock and Roll Hall of Fame in 1996 and the UK Music Hall of Fame in 2005. By 2013, the band had more than 250 million records worldwide. Roger Waters met Nick Mason while they were both studying architecture at the London Polytechnic at Regent Street and they first played music together in a group formed by Keith Noble and Clive Metcalfe with Nobles sister Sheilagh. Richard Wright, an architecture student, joined later that year. Waters played lead guitar, Mason drums, and Wright rhythm guitar, the band performed at private functions and rehearsed in a tearoom in the basement of the Regent Street Polytechnic. They performed songs by the Searchers and material written by their manager and songwriter, Mason moved out after the 1964 academic year, and guitarist Bob Klose moved in during September 1964, prompting Waters switch to bass. Sigma 6 went through several names, including the Meggadeaths, the Abdabs and the Screaming Abdabs, Leonards Lodgers, in 1964, as Metcalfe and Noble left to form their own band, guitarist Syd Barrett joined Klose and Waters at Stanhope Gardens. Barrett, two younger, had moved to London in 1962 to study at the Camberwell College of Arts. Waters and Barrett were childhood friends, Waters had often visited Barrett, Noble and Metcalfe left the Tea Set in late 1963, and Klose introduced the band to singer Chris Dennis, a technician with the Royal Air Force. In December 1964, they secured their first recording time, at a studio in West Hampstead, through one of Wrights friends, Wright, who was taking a break from his studies, did not participate in the session. When the RAF assigned Dennis a post in Bahrain in early 1965, later that year, they became the resident band at the Countdown Club near Kensington High Street in London, where from late night until early morning they played three sets of 90 minutes each
36.
Abbey Road Studios
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Abbey Road Studios is a recording studio at 3 Abbey Road, St Johns Wood, City of Westminster, London, England. It was established November 1931 by the Gramophone Company, a predecessor of British music company EMI, Abbey Road Studios is most notable as being the 1960s venue for innovative recording techniques adopted by the Beatles, Pink Floyd, the Hollies, Badfinger and others. One of its earliest world-famous-artist clients was Paul Robeson, who recorded December 1931, towards the end of 2009, the studio came under threat of sale to property developers. However, the British Government protected the site, granting it English Heritage Grade II listed status in 2010, originally a nine-bedroom Georgian townhouse built in 1831 on the footpath leading to Kilburn Abbey, the building was later converted to flats where the most flamboyant resident was Maundy Gregory. In 1931, the Gramophone Company acquired the premises and converted it into studios, pathé filmed the opening of the studios when Sir Edward Elgar conducted the London Symphony Orchestra in recording sessions of his music. In 1934, inventor of stereo sound, Alan Blumlein, recorded Mozarts Jupiter Symphony which was conducted by Sir Thomas Beecham at the studios, the neighbouring house is also owned by the studio and used to house musicians. During the mid-20th century, the studio was used by leading British conductor Sir Malcolm Sargent. The Gramophone Company amalgamated with Columbia Graphophone Company to form EMI and it was under this name that in 1936 cellist Pablo Casals became the first to record Johann Sebastian Bachs Cello Suites No.1 &2 at the command of EMI head Fred Gaisberg. The recordings went on to spur a revolution among Bach aficionados, in 1958, Studio Two at Abbey Road became a centre for rock and roll music when Cliff Richard and the Drifters recorded Move It there, and later pop music material. The Beatles named their 1969 album Abbey Road, after the street where the studio is located, the studio was renamed Abbey Road Studios in 1970 after the Beatles album had made it famous. Iain Macmillan took the cover photograph outside the studios, with the result that the nearby zebra crossing has become a place of pilgrimage for Beatles fans. It has been a tradition for visitors to pay homage to the band by writing on the wall in front of the even though it is painted over every three months. December 2010, the crossing at Abbey Road was given a Grade II listed status. Pink Floyd recorded most of their late 1960s to mid-1970s albums here, the Shadows named their Live at Abbey Road album after the studio, with the cover spoofing the Beatles album. The chief mastering engineer at Abbey Road was Chris Vinyl Blair, in 1979, EMI commissioned the British jazz fusion band Morrissey-Mullen to record Britains first digitally recorded single record at Abbey Road Studios. From July 18 to September 11,1983, the public had an opportunity to see inside the legendary Studio Two where The Beatles made most of their records. While a new mixing console was being installed in the control room, the soundtrack to the video had a number of recordings that were not made commercially available until the release of The Beatles Anthology project over a decade later. The Red Hot Chili Peppers used a photograph of the walking across the zebra crossing naked on the front of The Abbey Road E. P. which was released in 1988
37.
Bill Porter (sound engineer)
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In one week of 1960, his recordings accounted for 15 of Billboard Magazines Top 100, a feat none have matched. Porter mixed concert sound for Presley from 1970 until the death in 1977. Porter, said to have an ear, was inducted into the TEC Awards Hall of Fame in 1992. Porter was born Billy Rhodes Porter in St. Louis, Missouri on June 15,1931 and his family moved to Tennessee when he was 10. He grew up loving jazz music and baseball, and for a time considered a career starting with the minor leagues. He mixed up to four microphones for television broadcast for $92 per week, at nearby RCA Records in 1959, the chief engineer was transferred after angering Chet Atkins, and Porter applied for the position. In June 1959, he mixed The Three Bells for the Browns, with Atkins producing, without telling anyone, he spliced a different take with a good intro onto the beginning, and sent that version instead. Four decades later, Porter recalled his quick fix, this was a need-to-know situation, I had been in the business three months or something like that. Youre not an engineer until you destroy a master and hopefully live to talk about it. In July, the song went to one on the U. S. country and pop charts. Porter served for four years as the chief engineer under guitarist, Porter became the engineer big-name artists wanted to work with, and he was influential in creating the Nashville sound. Record producer Owen Bradley once asked Atkins how he got his sound and he recorded more than 579 records that charted—49 were top 10,11 were number one, and 37 were certified gold records. Most were recorded at what is now RCAs Studio B in Nashville, the studios acoustics were problematic, with resonant room modes creating an uneven frequency response. Adjacent to Studio B was a room containing a plate reverb device made by EMT. The EMT reverb was an echo chamber used to add artificial reverberation effects to recordings. So much signal was being sent to the plate that Porter disconnected the associated VU meter so that he would not be bothered with its needle slamming against its peg. Porter related that the EMTs springs frequently broke under the tension, and he would have to replace them. Porter recorded nearly all of Presleys number one hits upon the return from Army duty in 1960
38.
RCA Studio B
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RCA Studio B is a recording studio in Nashville, Tennessee. Originally known simply as RCA Studios, it became famous in the 1960s for being a part of what many refer to as the Nashville Sound, the National Park Service listed it on the National Register of Historic Places in 2012. Built by Dan Maddox in 1956, it was constructed at the request of Chet Atkins and Steve Sholes to facilitate the needs of RCA Victor Records and other record labels. According to Chet Atkins, the plans for the studio were drawn up on a napkin by Bill Miltenburg, RCAs chief engineer, construction took four months, and the studio was opened at the cost of $37,515. The recording studio is a building with offices occupying the front but the area of the studio. The studio itself measures 42.5 by 27 by 13, in 1960 and 1961 an addition was built to provide office space and rooms for tape mastering and a lacquer mastering lab. A larger studio was built on 17th avenue in 1964 that became known as Studio A, the first chief engineer was Bob Ferris, a man with a prickly personality who managed to make Atkins angry enough to have him moved elsewhere. Bill Porter replaced him at the end of March,1959, Porter considered the studios acoustics problematic, with resonant room modes creating an uneven frequency response. Porter also marked Xes on the floor where he discovered, by careful experimentation, Porter positioned lead vocalists, background vocalists and acoustic guitarists at microphones placed directly over his marks. After these improvements, Don Gibson recorded his album Girls, Guitars, Porter later told an interviewer, Everybody said, God, what a different sound. She noted that the spot where her car impacted the building is still visible, in 1977 the studio was made available to the Country Music Hall of Fame for tours, and in 1992 it was donated to the Country Music Hall of Fame by the late Dan Maddox. Until 2001, it was operated as an attraction when the new home for the Hall of Fame was built in downtown Nashville, now the studio is co-operated by the Country Music Hall of Fame and Belmont Universitys Mike Curb College of Entertainment and Music Business program. Students use the facilities for learning the basic techniques of analog recording. Nashville painter and singer/songwriter, Gil Veda, introduced to the Grand Ole Opry crowd as The Spanish Hank Williams in 1962, was the first Hispanic singer to record at RCA’s Studio B, daily tours of the studio are offered by the Country Music Hall of Fame and Museum. Following is a list of notable artists who recorded songs at Studio B
39.
Spring (device)
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A spring is an elastic object used to store mechanical energy. Springs are usually out of spring steel. There are a number of spring designs, in everyday usage the term often refers to coil springs. When a spring is compressed or stretched from its resting position, the rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve, an extension or compression springs rate is expressed in units of force divided by distance, for example lbf/in or N/m. A torsion spring is a spring that works by twisting, when it is twisted about its axis by an angle, a torsion springs rate is in units of torque divided by angle, such as N·m/rad or ft·lbf/degree. The inverse of spring rate is compliance, that is, if a spring has a rate of 10 N/mm, the stiffness of springs in parallel is additive, as is the compliance of springs in series. Springs are made from a variety of materials, the most common being spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel, some non-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosion resistance and beryllium copper for springs carrying electrical current. Simple non-coiled springs were used throughout history, e. g. the bow. In the Bronze Age more sophisticated spring devices were used, as shown by the spread of tweezers in many cultures, coiled springs appeared early in the 15th century, in door locks. The first spring powered-clocks appeared in that century and evolved into the first large watches by the 16th century, in 1676 British physicist Robert Hooke discovered Hookes law which states that the force a spring exerts is proportional to its extension. Compression spring – is designed to operate with a compression load, flat spring – this type is made of a flat spring steel. Machined spring – this type of spring is manufactured by machining bar stock with a lathe and/or milling operation rather than a coiling operation, since it is machined, the spring may incorporate features in addition to the elastic element. Machined springs can be made in the load cases of compression/extension, torsion. Serpentine spring - a zig-zag of thick wire - often used in modern upholstery/furniture, the most common types of spring are, Cantilever spring – a spring which is fixed only at one end. Coil spring or helical spring – a spring is of two types, Tension or extension springs are designed to become longer under load and their turns are normally touching in the unloaded position, and they have a hook, eye or some other means of attachment at each end. Compression springs are designed to become shorter when loaded and their turns are not touching in the unloaded position, and they need no attachment points
40.
Laurens Hammond
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Laurens Hammond, was an American engineer and inventor. His inventions include, most famously, the Hammond organ, the Hammond Clock, and the worlds first polyphonic musical synthesizer, Laurens Hammond was born in Evanston, Illinois, to William Andrew and Idea Louise Strong Hammond. Laurens showed his technical prowess from an early age. His father, William, took his own life in 1898, ostensibly due to the pressures of running the First National Bank, upon her husbands death, Idea, who was an artist, relocated to France with Laurens to further her studies. It was during their stay in France that Laurens began developing many of his early inventions, when the family returned to Evanston, Laurens, then 14, was as fluent in French and German as he was in his native tongue. By this time, he had designed a system for automatic transmission for automobiles. At his mothers suggestion, he submitted his designs to engineers at French automaker Renault, Hammond studied mechanical engineering at Cornell University, and was a member of the Delta Upsilon fraternity. He graduated with honors in 1916, following this, Hammond moved to Detroit, where he was fortunate to occupy the post of chief engineer for the Gray Motor Company, a manufacturer of marine engines. A partner in the company, Col. John H. Poole, with whom Hammond had served in France, knew of his engineering skills, in 1919, Hammond invented a silent spring-driven clock. This invention brought him money to leave Gray Motor Company. In 1922, Hammond invented the Teleview system of shutter glasses in association with 3-D films, one feature was made for the system, a film called Radio-Mania. Hammond premiered his show at the Selwyn Theatre in New York in December 1922 to critical acclaim, in 1928, Hammond founded the Hammond Clock Company, after designing a synchronous clock motor that was inspired by Henry Warrens Telechrons, but was not self-starting. These clocks were still popular in Britain in the 1960s, because they would not display a false time, the British generating stations also corrected the number of cycles at the end of the day so that Hammond clocks would be accurate. In 1933, he bought a piano, and proceeded to discard everything apart from the keyboard action. Using the keyboard as a controller, he was able to experiment with various sound-generating methods until he found the best one—the tonewheel generator. The companys assistant treasurer, W. L. Lahey, was the organist at the nearby St. Christophers Episcopal Church, thanks to Hammonds prior manufacturing and engineering experience, the tonewheel generator was extremely well-engineered by the time the organ finally went into production. The number of tonewheel organs still in use in the twenty-first century is a testament to the quality of the design. Hammond filed his patent application on January 19,1934, at that time, unemployment was a major problem due to the Great Depression, and with this in mind, the Patent Office rushed to grant Hammonds application, with the hope of creating jobs in the area
41.
Hammond organ
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The Hammond organ is an electric organ, invented by Laurens Hammond and John M. Hanert and first manufactured in 1935. Various models have been produced, most of use sliding drawbars to create a variety of sounds. Around two million Hammond organs have been manufactured, the organ is commonly used with, and associated with, the Leslie speaker. The organ was originally marketed and sold by the Hammond Organ Company to churches as a lower-cost alternative to the pipe organ. It quickly became popular with jazz musicians in organ trios. Organ trios were hired by jazz club owners, who found that organ trios were a cheaper alternative to hiring a big band. The Hammond Organ Company struggled financially during the 1970s as they abandoned tonewheel organs and these instruments were not as popular with musicians as the tonewheels had been, and the company went out of business in 1985. The Hammond name was purchased by the Suzuki Musical Instrument Corporation and this culminated in the production of the New B-3 in 2002, which provided an accurate recreation of the original B-3 organ using modern digital technology. Hammond-Suzuki continues to manufacture a variety of organs for both players and churches. Other companies, such as Korg, Roland and Clavia, have achieved success in providing emulations of the original tonewheel organs. The sound of a tonewheel Hammond can also be emulated using software such as Native Instruments B4. A number of distinctive Hammond organ features are not usually found on other keyboards like the piano or synthesizer, Some are similar to a pipe organ, but others are unique to the instrument. Most Hammond organs have two 61-note keyboards called manuals, as with pipe organ keyboards, the two manuals are arrayed on two levels close to each other. There is no difference in volume regardless of how heavily or lightly the key is pressed, the keys on each manual have a lightweight action, which allows players to perform rapid passages more easily than on a piano. In contrast to piano and pipe organ keys, Hammond keys have a flat-front profile, Early Hammond console models had sharp edges, but starting with the B-2 these were rounded, as they were cheaper to manufacture. The M series of spinets also had waterfall keys, but later models had diving board style keys which resembled those found on a church organ. Modern Hammond-Suzuki models use waterfall keys, Hammond console organs come with a wooden pedalboard played with the feet, for bass notes. Most console Hammond pedalboards have 25 notes, with the note a low C
42.
Guitar amplifier
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The input of modern guitar amplifiers is a 1/4 jack, which is fed a signal from an electro-magnetic pickup or a piezoelectric pickup using a patch cord, or a wireless transmitter. For electric guitar players, their choice of guitar amp and the settings they use on the amplifier are a key part of their signature tone or sound, some guitar players are longtime users of a specific amp brand or model. Many electric guitar players use external effects pedals to alter the sound of their tone before the signal reaches the guitar amp, such as the wah wah pedal and this article focuses on electric guitar amps. For information on amps for guitar, a lower-pitched, similar instrument. More expensive amplifiers typically have controls for other frequency ranges. Some guitar amplifiers have a graphic equalizer, which uses vertical fader controls which can control many frequency bands, the first amplifier stage is a preamplifier stage, which amplifies the guitar signal to a level that can drive the power stage. The power amplifier or output stage produces a current signal to drive a loudspeaker to produce sound that the guitarist. Amplifiers may use vacuum tubes, solid-state devices, or both, a wide range of speaker configurations are available in guitar cabinets, ranging from cabinets with a single speaker or multiple speakers. Guitar amplifiers have a range in price and quality. Music equipment companies import small, low-powered practice amplifiers for students, other companies produce expensive custom-made amplifiers for professional musicians, which can cost thousands of dollars. Most combo amplifiers have a handle, and many combo amplifiers. Control knobs are typically mounted on the front of the cabinet or chassis, though in some cases, the most basic amps only have a few knobs, which typically control volume, bass and treble. More expensive amps may have a number of knobs that control pre-amp volume, distortion or overdrive, volume, bass, mid and treble, some older amps have a knob that controls a vibrato effect. The 1/4 input jack is typically mounted on the front of the amplifier, in the simplest, least expensive amplifiers, this 1/4 jack is the only jack on the amplifier. Some amps have a 1/4 jack for connecting a pedal to turn the amps onboard overdrive and reverb on, the cone speaker, widely used in 2000s-era amp cabinets, was not offered for sale until 1925. The first amplifiers and speakers could only be powered with large batteries, when engineers developed the first AC mains-powered amplifiers, they were soon used to make musical instruments louder. Engineers invented the first loud, powerful amplifier and speaker systems for public address systems and these large PA systems and movie theatre sound systems were very large and very expensive, and so they could not be used by most touring musicians. During the late 1920s to mid-1930s, small portable PA systems, in 1928, the Stromberg-Voisinet firm was the first company to sell an electric stringed instrument and amplifier package
43.
Digital signal processing
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Digital signal processing is the use of digital processing, such as by computers, to perform a wide variety of signal processing operations. The signals processed in this manner are a sequence of numbers that represent samples of a variable in a domain such as time, space. Digital signal processing and analog signal processing are subfields of signal processing, digital signal processing can involve linear or nonlinear operations. Nonlinear signal processing is closely related to system identification and can be implemented in the time, frequency. DSP is applicable to both streaming data and static data, the increasing use of computers has resulted in the increased use of, and need for, digital signal processing. To digitally analyze and manipulate an analog signal, it must be digitized with an analog-to-digital converter, sampling is usually carried out in two stages, discretization and quantization. Discretization means that the signal is divided into equal intervals of time, quantization means each amplitude measurement is approximated by a value from a finite set. Rounding real numbers to integers is an example, the Nyquist–Shannon sampling theorem states that a signal can be exactly reconstructed from its samples if the sampling frequency is greater than twice the highest frequency of the signal. In practice, the frequency is often significantly higher than twice that required by the signals limited bandwidth. Theoretical DSP analyses and derivations are typically performed on discrete-time signal models with no amplitude inaccuracies, numerical methods require a quantized signal, such as those produced by an analog-to-digital converter. The processed result might be a frequency spectrum or a set of statistics, but often it is another quantized signal that is converted back to analog form by a digital-to-analog converter. In DSP, engineers usually study digital signals in one of the domains, time domain, spatial domain, frequency domain. They choose the domain in which to process a signal by making an assumption as to which domain best represents the essential characteristics of the signal. The most common processing approach in the time or space domain is enhancement of the signal through a method called filtering. Digital filtering generally consists of linear transformation of a number of surrounding samples around the current sample of the input or output signal. There are various ways to characterize filters, for example, A linear filter is a transformation of input samples. A causal filter uses only samples of the input or output signals. A non-causal filter can usually be changed into a filter by adding a delay to it
