Acoustic signature is used to describe a combination of acoustic emissions of sound emitters, such as those of ships and submarines. In addition, aircraft and living animals can be described as having their own characteristic acoustic signatures or sound attributes, which can be used to study their condition and physical location; the analysis of acoustic signatures is an important adjunct to passive sonar used to track naval warships and weapons. Similar methods have been used to identify aircraft before the development of sophisticated radar tracking; the acoustic signature is made up of a number of individual elements. These include: Machinery noise: noise generated by a ship's engines, propeller shafts, fuel pumps, air conditioning systems, etc. Cavitation noise: noise generated by the creation of gas bubbles by the turning of a ship's propellers. Hydrodynamic noise: noise generated by the movement of water displaced by the hull of a moving vessel; these emissions depend on the installed machinery and ship's displacement.
Therefore, different ship classes will have different combinations of acoustic signals that together form a unique signature. Hydrophones and sonar operating in passive mode can detect acoustic signals radiated by otherwise invisible submarines, use these signals to target attacks. Modern naval mines and torpedoes such as the CAPTOR mine can be programmed to distinguish the acoustic signatures of different vessels, leaving friendly vessels unmolested and attacking high-value targets when faced with multiple possible targets, e.g. distinguishing an aircraft carrier from its escorts. Warship designers aim to reduce the acoustic signature of ships and submarines just as much as they aim to reduce the radar cross sections and infra-red signals. For submarines, as a prime factor in how they can be detected the reduction of the acoustic signature is a primary goal; the acoustic signature can be reduced by fitting of machinery with the best possible mechanical tolerances and designed to produce a minimum of noise.
Decoupling the machinery from the hull by mounting machinery on rubber mounting blocks. Designing propellers to reduce cavitation, this led to the development of large slow turning propellers, today there is a preference now for pump-jet propulsors over propellers; the fitting of anechoic tiles to the hull, however ill fitting and loose anechoic tiles can themselves be a source of noise. Hydrodynamic efficiency to minimise the perturbation of water. Care in minimising protrusions from the hull. For a time the Royal Navy toyed with the idea of the trimaran hulled Future Surface Combatant; these would have had a low acoustic signature. With three blade like hulls these ships would have cut through the water with a minimum of hydrodynamic noise. Radiated mechanical noise would be minimised by using propulsors powered by a diesel-electric power plant; this project got as far as the construction of the research ship RV Triton to test the principle of a large scale trimaran design. Sonar Underwater acoustics Stealth ship Type 45 destroyer Anti-submarine warfare Submarine warfare Type 212 submarine Teardrop hull Spectrogram
Radio broadcasting is transmission by radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both; the signal types can be digital audio. The earliest radio stations did not carry audio. For audio broadcasts to be possible, electronic detection and amplification devices had to be incorporated; the thermionic valve was invented in 1904 by the English physicist John Ambrose Fleming. He developed a device he called an "oscillation valve"; the heated filament, or cathode, was capable of thermionic emission of electrons that would flow to the plate when it was at a higher voltage. Electrons, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons. Known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector; this improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker.
However, what was still required was an amplifier. The triode was patented on March 4, 1906, by the Austrian Robert von Lieben independent from that, on October 25, 1906, Lee De Forest patented his three-element Audion, it wasn't put to practical use until 1912 when its amplifying ability became recognized by researchers. By about 1920, valve technology had matured to the point where radio broadcasting was becoming viable. However, an early audio transmission that could be termed a broadcast may have occurred on Christmas Eve in 1906 by Reginald Fessenden, although this is disputed. While many early experimenters attempted to create systems similar to radiotelephone devices by which only two parties were meant to communicate, there were others who intended to transmit to larger audiences. Charles Herrold started broadcasting in California in 1909 and was carrying audio by the next year.. In The Hague, the Netherlands, PCGG started broadcasting on November 6, 1919, making it, arguably the first commercial broadcasting station.
In 1916, Frank Conrad, an electrical engineer employed at the Westinghouse Electric Corporation, began broadcasting from his Wilkinsburg, Pennsylvania garage with the call letters 8XK. The station was moved to the top of the Westinghouse factory building in East Pittsburgh, Pennsylvania. Westinghouse relaunched the station as KDKA on November 2, 1920, as the first commercially licensed radio station in America; the commercial broadcasting designation came from the type of broadcast license. The first licensed broadcast in the United States came from KDKA itself: the results of the Harding/Cox Presidential Election; the Montreal station that became CFCF began broadcast programming on May 20, 1920, the Detroit station that became WWJ began program broadcasts beginning on August 20, 1920, although neither held a license at the time. In 1920, wireless broadcasts for entertainment began in the UK from the Marconi Research Centre 2MT at Writtle near Chelmsford, England. A famous broadcast from Marconi's New Street Works factory in Chelmsford was made by the famous soprano Dame Nellie Melba on 15 June 1920, where she sang two arias and her famous trill.
She was the first artist of international renown to participate in direct radio broadcasts. The 2MT station began to broadcast regular entertainment in 1922; the BBC was amalgamated in 1922 and received a Royal Charter in 1926, making it the first national broadcaster in the world, followed by Czech Radio and other European broadcasters in 1923. Radio Argentina began scheduled transmissions from the Teatro Coliseo in Buenos Aires on August 27, 1920, making its own priority claim; the station got its license on November 19, 1923. The delay was due to the lack of official Argentine licensing procedures before that date; this station continued regular broadcasting of entertainment and cultural fare for several decades. Radio in education soon followed and colleges across the U. S. began adding radio broadcasting courses to their curricula. Curry College in Milton, Massachusetts introduced one of the first broadcasting majors in 1932 when the college teamed up with WLOE in Boston to have students broadcast programs.
Broadcasting service is – according to Article 1.38 of the International Telecommunication Union´s Radio Regulations – defined as «A radiocommunication service in which the transmission are intended for direct reception by the general public. This service may include sound transmissions, television transmissions or other types of transmission.» Definitions identical to those contained in the Annexes to the Constitution and Convention of the International Telecommunication Union are marked "" or "" respectively. A radio broadcasting station is associated with wireless transmission, though in practice broadcasting transmission take place using both wires and radio waves; the point of this is that anyone with the appropriate receiving technology can receive the broadcast. In line to ITU Radio Regulations each broadcasting station shall be classified by the service in which it operates permanently or temporarily. Broadcasting by radio takes several forms; these include FM stations. There are several subtypes, namely commercial broadcasting, non-commercial educational public broadcasting and non-profit varieties as well as community radio, student-run campus radio stations, and
Folk music includes traditional folk music and the genre that evolved from it during the 20th-century folk revival. Some types of folk music may be called world music. Traditional folk music has been defined in several ways: as music transmitted orally, music with unknown composers, or music performed by custom over a long period of time, it has been contrasted with classical styles. The term originated in the 19th century. Starting in the mid-20th century, a new form of popular folk music evolved from traditional folk music; this process and period is reached a zenith in the 1960s. This form of music is sometimes called contemporary folk music or folk revival music to distinguish it from earlier folk forms. Smaller, similar revivals have occurred elsewhere in the world at other times, but the term folk music has not been applied to the new music created during those revivals; this type of folk music includes fusion genres such as folk rock, folk metal, others. While contemporary folk music is a genre distinct from traditional folk music, in U.
S. English it shares the same name, it shares the same performers and venues as traditional folk music; the terms folk music, folk song, folk dance are comparatively recent expressions. They are extensions of the term folklore, coined in 1846 by the English antiquarian William Thoms to describe "the traditions and superstitions of the uncultured classes"; the term further derives from the German expression volk, in the sense of "the people as a whole" as applied to popular and national music by Johann Gottfried Herder and the German Romantics over half a century earlier. Though it is understood that folk music is music of the people, observers find a more precise definition to be elusive; some do not agree that the term folk music should be used. Folk music may tend to have certain characteristics but it cannot be differentiated in purely musical terms. One meaning given is that of "old songs, with no known composers", another is that of music, submitted to an evolutionary "process of oral transmission....
The fashioning and re-fashioning of the music by the community that give it its folk character". Such definitions depend upon " processes rather than abstract musical types...", upon "continuity and oral transmission...seen as characterizing one side of a cultural dichotomy, the other side of, found not only in the lower layers of feudal and some oriental societies but in'primitive' societies and in parts of'popular cultures'". One used definition is "Folk music is what the people sing". For Scholes, as well as for Cecil Sharp and Béla Bartók, there was a sense of the music of the country as distinct from that of the town. Folk music was "...seen as the authentic expression of a way of life now past or about to disappear" in "a community uninfluenced by art music" and by commercial and printed song. Lloyd rejected this in favour of a simple distinction of economic class yet for him true folk music was, in Charles Seeger's words, "associated with a lower class" in culturally and stratified societies.
In these terms folk music may be seen as part of a "schema comprising four musical types:'primitive' or'tribal'. Music in this genre is often called traditional music. Although the term is only descriptive, in some cases people use it as the name of a genre. For example, the Grammy Award used the terms "traditional music" and "traditional folk" for folk music, not contemporary folk music. Folk music may include most indigenous music. From a historical perspective, traditional folk music had these characteristics: It was transmitted through an oral tradition. Before the 20th century, ordinary people were illiterate; this was not mediated by books or recorded or transmitted media. Singers may extend their repertoire using broadsheets or song books, but these secondary enhancements are of the same character as the primary songs experienced in the flesh; the music was related to national culture. It was culturally particular. In the context of an immigrant group, folk music acquires an extra dimension for social cohesion.
It is conspicuous in immigrant societies, where Greek Australians, Somali Americans, Punjabi Canadians, others strive to emphasize their differences from the mainstream. They learn songs and dances that originate in the countries their grandparents came from, they commemorate personal events. On certain days of the year, such as Easter, May Day, Christmas, particular songs celebrate the yearly cycle. Weddings and funerals may be noted with songs and special costumes. Religious festivals have a folk music component. Choral music at these events brings children and non-professional singers to participate in a public arena, giving an emotional bonding, unrelated to the aesthetic qualities of the music; the songs have been performed, by custom, over a long period of time several generations. As a side-effect, the following characteristics are sometimes present: There is no copyright on the songs. Hundreds of folk songs from the 19th century have known authors but have continued in oral tradition to the point where they are considered traditional for purposes of music publishing.
This has become much less frequent since the 1940s. Today every folk song, recorded is credited with an arranger. Fusion of cultures: Because cultures interact and change over time
In music, sampling is the reuse of a portion or sample of a sound recording in another recording. Samples may comprise rhythm, speech, or other sounds, they are integrated using hardware or software such as digital audio workstations. A process similar to sampling originated in the 1940s with musique concrète, experimental music created by splicing and looping tape; the term sampling was coined by in the late 1970s by the creators of the Fairlight CMI, an influential early sampler that became a staple of 1980s pop music. The 1988 release of the first Akai MPC, an affordable sampler with an intuitive interface, made sampling accessible to a wider audience. Sampling is a foundation of hip hop music, with producers sampling funk and soul records drum breaks, which could be rapped over. Musicians have created albums assembled from samples, such as DJ Shadow's 1996 album Endtroducing; the practice has influenced all genres of music and is important to electronic music, hip hop and pop. Sampling without permission can infringe copyright.
The process of acquiring permission for a sample is known as clearance, which can be a complex and costly process. Landmark legal cases, such as Grand Upright Music, Ltd. v. Warner Bros. Records Inc in 1991, changed how samples are used; as the court ruled that unlicensed sampling constitutes copyright infringement, samples from well known sources are now prohibitively expensive. In the 1940s, Pierre Schaeffer developed musique concrète, an experimental form of music created by recording sounds to tape, splicing them, manipulating them to create sound collages, he created pieces using recordings of sounds including the human body and kitchen utensils. The method involved the creation of tape loops, splicing lengths of tape end to end, by which a sound could be played indefinitely. Schaeffer developed a tape recorder, the Phonogene, which played loops at twelve different pitches triggered by a keyboard. Composers including John Cage, Edgar Varèse, Karheinz Stockhausen and Iannis Xenakis experimented with musique concrète, Bebe and Louis Barron used it to create the first electronic film soundtrack, for the 1956 science fiction film Forbidden Planet.
It was brought to a mainstream audience by the BBC Radiophonic Workshop, which used these early sampling techniques to produce soundtracks for shows including Doctor Who. In the 1960s, Jamaican dub reggae producers such as King Tubby and Lee "Scratch" Perry began using pre-recorded samples of reggae rhythms to produce riddim tracks, which were deejayed over. Jamaican immigrants introduced dub sampling techniques to American hip hop music in the 1970s; the term sampling was coined by in the late 1970s by Kim Ryrie and Peter Vogel to describe a feature of their Fairlight CMI synthesizer. Designers of early samplers used the term to describe the technical process of the instruments, rather than to describe how users would use the feature. While developing the Fairlight, Vogel sampled around a second of a piano piece from a radio broadcast, discovered that he could imitate a real piano by playing the sample back at different pitches, he recalled in 2005: It sounded remarkably like a piano, a real piano.
This had never been done before... By today's standards it was a pretty awful piano sound, but at the time it was a million times more like a piano than anything any synthesiser had churned out. So I realised that we didn't have to bother with all the synthesis stuff. Just take the sounds, whack them in the memory and away you go. Compared to samplers, the Fairlight offered limited control over samples, it allowed control over pitch and envelope, could only record a few seconds of sound. However, its ability to sample and play back acoustic sounds became its most popular feature. Though the concept of reusing recordings in larger recordings was not new, the Fairlight's built-in sequencer and design made the process simple. According to the Guardian, the Fairlight was the "first world-changing sampler". Though it was it was unaffordable for most hobbyists, early users included Kate Bush, Peter Gabriel, Thomas Dolby, Duran Duran, Herbie Hancock, Todd Rundgren and Ebn Ozn. An early pulse-code modulation digital sampler was Toshiba's LMD-649, created in 1981 by engineer Kenji Murata for Japanese electronic music band Yellow Magic Orchestra, who used it for extensive sampling and looping in their 1981 album Technodelic.
The LMD-649 played and recorded PCM samples at 12-bit audio depth and 50 kHz sampling rate, stored in 128 KB of dynamic RAM. The success of the Fairlight inspired competitors, improving the technology and driving down prices dramatically. Early competitors included the E-mu Emulator and the Akai S950. Drum machines such as the Oberheim DMX and Linn LM-1 began incorporating samples of drum kits rather than generating sounds from circuits; the designers of early samplers anticipated that users would sample short sounds, such as drum hits or individual notes, to use as "building blocks" for compositions. However and producers began sampling longer passages of music. In the words of Greg Milner, author of Perfecting Sound Forever, "They didn't just want the sound of John Bonham's kick drum, they wanted to loop and repeat the whole of'When the Levee Breaks'." Roger Linn, designer of the LM-1 and MPC, said: "It was a pleasant surprise. After sixty years of recording, there are so many. Why reinvent the wheel?"In response to demand, samplers such as E-mu's SP-1200 were developed to allow users to store longer samples.
In 1988, Akai released the first MPC sampler, which allowed artists to assign samples to separate pads and trigger them independently to playing a keyboard or drum kit. It h
A spectrogram is a visual representation of the spectrum of frequencies of a signal as it varies with time. When applied to an audio signal, spectrograms are sometimes called sonographs, voiceprints, or voicegrams; when the data is represented in a 3D plot they may be called waterfalls. Spectrograms are used extensively in the fields of music, sonar and speech processing and others. Spectrograms of audio can be used to identify spoken words phonetically, to analyse the various calls of animals. A spectrogram can be generated by an optical spectrometer, a bank of band-pass filters, by Fourier transform or by a wavelet transform. A spectrogram is depicted as a heat map, i.e. as an image with the intensity shown by varying the colour or brightness. A common format is a graph with two geometric dimensions: one axis represents time or RPM, the other axis is frequency. There are many variations of format: sometimes the vertical and horizontal axes are switched, so time runs up and down; the frequency and amplitude axes can be either linear or logarithmic, depending on what the graph is being used for.
Audio would be represented with a logarithmic amplitude axis, frequency would be linear to emphasize harmonic relationships, or logarithmic to emphasize musical, tonal relationships. Spectrograms of light may be created directly using an optical spectrometer over time. Spectrograms may be created from a time-domain signal in one of two ways: approximated as a filterbank that results from a series of band-pass filters, or calculated from the time signal using the Fourier transform; these two methods form two different time–frequency representations, but are equivalent under some conditions. The bandpass filters method uses analog processing to divide the input signal into frequency bands. Creating a spectrogram using the FFT is a digital process. Digitally sampled data, in the time domain, is broken up into chunks, which overlap, Fourier transformed to calculate the magnitude of the frequency spectrum for each chunk; each chunk corresponds to a vertical line in the image. These spectrums or time plots are "laid side by side" to form the image or a three-dimensional surface, or overlapped in various ways, i.e. windowing.
This process corresponds to computing the squared magnitude of the short-time Fourier transform of the signal s — that is, for a window width ω, s p e c t r o g r a m = | S T F T | 2. From the formula above, it appears that a spectrogram contains no information about the exact, or approximate, phase of the signal that it represents. For this reason, it is not possible to reverse the process and generate a copy of the original signal from a spectrogram, though in situations where the exact initial phase is unimportant it may be possible to generate a useful approximation of the original signal; the Analysis & Resynthesis Sound Spectrograph is an example of a computer program that attempts to do this. The Pattern Playback was an early speech synthesizer, designed at Haskins Laboratories in the late 1940s, that converted pictures of the acoustic patterns of speech back into sound. In fact, there is some phase information in the spectrogram, but it appears in another form, as time delay, the dual of the Instantaneous Frequency.
The size and shape of the analysis window can be varied. A smaller window will produce more accurate results in timing, at the expense of precision of frequency representation. A larger window will provide a more precise frequency representation, at the expense of precision in timing representation; this is an instance of the Heisenberg uncertainty principle, that the product of the precision in two conjugate variables is less than or equal to a constant. Early analog spectrograms were applied to a wide range of areas including the study of bird calls, with current research continuing using modern digital equipment and applied to all animal sounds. Contemporary use of the digital spectrogram is useful for studying frequency modulation in animal calls; the distinguishing characteristics of FM chirps, broadband clicks, social harmonizing are most visualized with the spectrogram. Spectrograms are useful in assisting in overcoming speech deficits and in speech training for the portion of the population, profoundly deaf The studies of phonetics and speech synthesis are facilitated through the use of spectrograms.
By reversing the process of producing a spectrogram, it is possible to create a
Advertising is a marketing communication that employs an sponsored, non-personal message to promote or sell a product, service or idea. Sponsors of advertising are businesses wishing to promote their products or services. Advertising is differentiated from public relations in that an advertiser pays for and has control over the message, it differs from personal selling in that the message is non-personal, i.e. not directed to a particular individual. Advertising is communicated through various mass media, including traditional media such as newspapers, television, outdoor advertising or direct mail; the actual presentation of the message in a medium is referred to as an advertisement, or "ad" or advert for short. Commercial ads seek to generate increased consumption of their products or services through "branding", which associates a product name or image with certain qualities in the minds of consumers. On the other hand, ads that intend to elicit an immediate sale are known as direct-response advertising.
Non-commercial entities that advertise more than consumer products or services include political parties, interest groups, religious organizations and governmental agencies. Non-profit organizations may use free modes such as a public service announcement. Advertising may help to reassure employees or shareholders that a company is viable or successful. Modern advertising originated with the techniques introduced with tobacco advertising in the 1920s, most with the campaigns of Edward Bernays, considered the founder of modern, "Madison Avenue" advertising. Worldwide spending on advertising in 2015 amounted to an estimated US$529.43 billion. Advertising's projected distribution for 2017 was 40.4% on TV, 33.3% on digital, 9% on newspapers, 6.9% on magazines, 5.8% on outdoor and 4.3% on radio. Internationally, the largest advertising-agency groups are Dentsu, Omnicom, WPP. In Latin, advertere means "to turn towards". Egyptians used papyrus to make sales messages and wall posters. Commercial messages and political campaign displays have been found in the ruins of Pompeii and ancient Arabia.
Lost and found advertising on papyrus was common in ancient ancient Rome. Wall or rock painting for commercial advertising is another manifestation of an ancient advertising form, present to this day in many parts of Asia and South America; the tradition of wall painting can be traced back to Indian rock art paintings that date back to 4000 BC. In ancient China, the earliest advertising known was oral, as recorded in the Classic of Poetry of bamboo flutes played to sell confectionery. Advertisement takes in the form of calligraphic signboards and inked papers. A copper printing plate dated back to the Song dynasty used to print posters in the form of a square sheet of paper with a rabbit logo with "Jinan Liu's Fine Needle Shop" and "We buy high-quality steel rods and make fine-quality needles, to be ready for use at home in no time" written above and below is considered the world's earliest identified printed advertising medium. In Europe, as the towns and cities of the Middle Ages began to grow, the general population was unable to read, instead of signs that read "cobbler", "miller", "tailor", or "blacksmith", images associated with their trade would be used such as a boot, a suit, a hat, a clock, a diamond, a horseshoe, a candle or a bag of flour.
Fruits and vegetables were sold in the city square from the backs of carts and wagons and their proprietors used street callers to announce their whereabouts. The first compilation of such advertisements was gathered in "Les Crieries de Paris", a thirteenth-century poem by Guillaume de la Villeneuve. In the 18th century advertisements started to appear in weekly newspapers in England; these early print advertisements were used to promote books and newspapers, which became affordable with advances in the printing press. However, false advertising and so-called "quack" advertisements became a problem, which ushered in the regulation of advertising content. Thomas J. Barratt of London has been called "the father of modern advertising". Working for the Pears Soap company, Barratt created an effective advertising campaign for the company products, which involved the use of targeted slogans and phrases. One of his slogans, "Good morning. Have you used Pears' soap?" was famous in its day and into the 20th century.
Barratt introduced many of the crucial ideas that lie behind successful advertising and these were circulated in his day. He stressed the importance of a strong and exclusive brand image for Pears and of emphasizing the product's availability through saturation campaigns, he understood the importance of reevaluating the market for changing tastes and mores, stating in 1907 that "tastes change, fashions change, the advertiser has to change with them. An idea, effective a generation ago would fall flat and unprofitable if presented to the public today. Not that the idea of today is always better than the older idea, but it is different – it hits the present taste."As the economy expanded across the world during the 19th century, advertising grew alongside. In the United States, the success of this advertising format led to the growth of mail-order advertising. In June 1836, French newspaper La Presse was the first to include paid advertising in its pages, allowing it to lower its price, extend its readership and increase its profitability and the formula was soon copied by all titles.
Around 1840, Volney B. Palmer established the roo
A frequency band is an interval in the frequency domain, delimited by a lower frequency and an upper frequency. The term may refer to an interval of some other spectrum; the frequency range of a system is the range over which it is considered to provide satisfactory performance, such as a useful level of signal with acceptable distortion characteristics. A listing of the upper and lower limits of frequency limits for a system is not useful without a criterion for what the range represents. Many systems are characterized by the range of frequencies. Musical instruments produce different ranges of notes within the hearing range; the electromagnetic spectrum can be divided into many different ranges such as visible light, infrared or ultraviolet radiation, radio waves, X-rays and so on, each of these ranges can in turn be divided into smaller ranges. A radio communications signal must occupy a range of frequencies carrying most of its energy, called its bandwidth. A frequency band may be subdivided into many.
Allocation of radio frequency ranges to different uses is a major function of radio spectrum allocation