Health effects from noise
Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Elevated workplace or environmental noise can cause hearing impairment, hypertension, ischemic heart disease and sleep disturbance. Changes in the immune system and birth defects have been attributed to noise exposure. Although age-related health effects occur with age, in many countries the cumulative impact of noise is sufficient to impair the hearing of a large fraction of the population over the course of a lifetime. Noise exposure has been known to induce tinnitus, hypertension and other cardiovascular adverse effects. Chronic noise exposure has been associated with sleep disturbances and increased incidence of diabetes. Adverse cardiovascular effects occur from chronic exposure to noise due to the sympathetic nervous system's inability to habituate; the sympathetic nervous system maintains lighter stages of sleep when the body is exposed to noise, which does not allow blood pressure to follow the normal rise and fall cycle of an undisturbed circadian rhythm.
Stress from time spent around elevated noise levels has been linked with increased workplace accident rates and aggression and other anti-social behaviors. The most significant sources are vehicles, prolonged exposure to loud music, industrial noise. There are an 10,000 deaths per year as a result of noise in the European Union. Noise-induced hearing loss is a permanent shift in pure-tone thresholds, resulting in sensorineural hearing loss; the severity of a threshold shift is dependent on severity of noise exposure. Noise-induced threshold shifts are seen as a notch on an audiogram from 3000–6000 Hz, but most at 4000 Hz. Exposure to loud noises, either in a single traumatic experience or over time, can damage the auditory system and result in hearing loss and sometimes tinnitus as well. Traumatic noise exposure can happen at work, at play, and/or by accident Noise induced hearing loss is sometimes unilateral and causes patients to lose hearing around the frequency of the triggering sound trauma.
Tinnitus is an auditory disorder characterized by the perception of a sound in the ear in the absence of an external sound source. There are two types of tinnitus: objective. Subjective can only be heard "in the head" by the person affected. Objective tinnitus can be heard from those around the affected person. Though the pathophysiology of tinnitus isn't known, noise exposure can be a contributing factor. Noise-induced tinnitus can be temporary or permanent depending on the type and amount of noise a person was exposed to. Noise has been associated with important cardiovascular health problems hypertension. Noise levels of 50 dB at night may increase the risk of myocardial infarction by chronically elevating cortisol production. Roadway noise levels are sufficient to constrict arterial blood flow and lead to elevated blood pressure. Vasoconstriction can result through medical stress reactions. Causal relationships have been discovered between noise and psychological effects such as annoyance, psychiatric disorders, effects on psychosocial well-being.
Exposure to intense levels of noise can cause violent reactions. Noise has been shown to be a factor that attributed to violent reactions; the psychological impacts of noise include an addiction to loud music. This was researched in a study where non-professional musicians were found to have loudness addictions more than non-musician control subjects. Psychological health effects from noise include anxiety. Individuals who have hearing loss, including noise induced hearing loss, may have their symptoms alleviated with the use of hearing aids. Individuals who do not seek treatment for their loss are 50% more to have depression than their aided peers; these psychological effects can lead to detriments in physical care in the form of reduced self-care, work-tolerance, increased isolation. Auditory stimuli can serve as psychological triggers for individuals with post traumatic stress disorder. Research commissioned by Rockwool, a multi-national insulation manufacturer headquartered in Denmark, reveals that in the UK one third of victims of domestic disturbances claim loud parties have left them unable to sleep or made them stressed in the last two years.
Around one in eleven of those affected by domestic disturbances claims it has left them continually disturbed and stressed. More than 1.8 million people claim noisy neighbours have made their life a misery and they cannot enjoy their own homes. The impact of noise on health is a significant problem across the UK given that more than 17.5 million Britons have been disturbed by the inhabitants of neighbouring properties in the last two year. For one in ten Britons this is a regular occurrence; the extent of the problem of noise pollution for public health is reinforced by figures collated by Rockwool from local authority responses to a Freedom of Information Act request. This research reveals in the period April 2008 - 2009 UK councils received 315,838 complaints about noise pollution from private residences; this resulted in environmental health officers across the UK serving 8,069 noise abatement notices, or citations under the terms of the Anti-Social Behaviour Act. Westminster City Council has received more complaints per head of population than any other district in the UK with 9,814 grievances about noise, which equates to 42.32 c
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. Pink noise is the most common signal in biological systems. In pink noise, each octave carries an equal amount of noise energy; the name arises from the pink appearance of visible light with this power spectrum. This is in contrast with white noise. Within the scientific literature the term pink noise is sometimes used a little more loosely to refer to any noise with a power spectral density of the form S ∝ 1 f α, where f is frequency, 0 < α < 2, with exponent α close to 1. These pink-like noises occur 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 corresponds to a much more basic distinction. The former come from condensed-matter systems in quasi-equilibrium, as discussed below; the latter correspond to a wide range of non-equilibrium driven dynamical systems.
The term flicker noise is sometimes used to refer to pink noise, although this is more properly applied only to its occurrence in electronic devices. Mandelbrot and Van Ness proposed the name fractional noise to emphasize that the exponent of the power spectrum could take non-integer values and be related to fractional Brownian motion, but the term is rarely used. 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; the human auditory system, which processes frequencies in a logarithmic fashion approximated by the Bark scale, does not perceive different frequencies with equal sensitivity. However, humans still differentiate between white pink noise with ease. Graphic equalizers divide signals into bands logarithmically and report power by octaves. Systems that do not have a flat response can be equalized by creating an inverse filter using a graphic equalizer.
Because pink noise has a tendency to occur in natural physical systems, it is useful in audio production. Pink noise can be processed, and/or effects can be added to produce desired sounds. Pink-noise generators are commercially available. One parameter of noise, the peak versus average energy contents, or crest factor, is important for testing purposes, such as for audio power amplifier and loudspeaker capabilities because the signal power is a direct function of the crest factor. 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, the power spectrum is reciprocal to f n. 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 two-dimensional, the area of the power spectrum covered by succeeding octaves is four times as large. 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, resistivity in solid-state electronics. 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. Sounds in nature are not musical in that they tend to be either too chaotic; the answer to this question was given in a statistical sense by Voss and Clarke, who showed that pitch and loudness fluctuations in speech and music are pink noises. So music is like tides not in how tide heights vary; because pink noise occurs in many physical and economic systems, some researchers describe it as being ubiquitous.
In physical systems, it is present in some meteorological data series, the electromagnetic radiation output of some astronomical bodies, in all electronic devices. In biological systems, it is present in, for example, heart beat rhythms, neural activity, the statistics of DNA sequences, as a generalized pattern. In financial systems, it is referred to as a long-term memory effect, it describes the statistical structure of many natural images. Pink noise has been applied to the modeling of mental states in psychology, used to explain stylistic variations in music from different cultures and historic periods. Richard F. Voss and J. Clarke claim that all musical melodies, w
In physics, power is the rate of doing work or of transferring heat, i.e. the amount of energy transferred or converted per unit time. Having no direction, it is a scalar quantity. In the International System of Units, the unit of power is the joule per second, known as the watt in honour of James Watt, the eighteenth-century developer of the condenser steam engine. Another common and traditional measure is horsepower. Being the rate of work, the equation for power can be written: power = work time As a physical concept, power requires both a change in the physical system and a specified time in which the change occurs; this is distinct from the concept of work, only measured in terms of a net change in the state of the physical system. The same amount of work is done when carrying a load up a flight of stairs whether the person carrying it walks or runs, but more power is needed for running because the work is done in a shorter amount of time; the output power of an electric motor is the product of the torque that the motor generates and the angular velocity of its output shaft.
The power involved in moving a vehicle is the product of the traction force of the wheels and the velocity of the vehicle. The rate at which a light bulb converts electrical energy into light and heat is measured in watts—the higher the wattage, the more power, or equivalently the more electrical energy is used per unit time; the dimension of power is energy divided by time. The SI unit of power is the watt, equal to one joule per second. Other units of power include ergs per second, metric horsepower, foot-pounds per minute. One horsepower is equivalent to 33,000 foot-pounds per minute, or the power required to lift 550 pounds by one foot in one second, is equivalent to about 746 watts. Other units include a logarithmic measure relative to a reference of 1 milliwatt. Power, as a function of time, is the rate at which work is done, so can be expressed by this equation: P = d W d t where P is power, W is work, t is time; because work is a force F applied over a distance x, W = F ⋅ x for a constant force, power can be rewritten as: P = d W d t = d d t = F ⋅ d x d t = F ⋅ v In fact, this is valid for any force, as a consequence of applying the fundamental theorem of calculus.
As a simple example, burning one kilogram of coal releases much more energy than does detonating a kilogram of TNT, but because the TNT reaction releases energy much more it delivers far more power than the coal. If ΔW is the amount of work performed during a period of time of duration Δt, the average power Pavg over that period is given by the formula P a v g = Δ W Δ t, it is the average amount of energy converted per unit of time. The average power is simply called "power" when the context makes it clear; the instantaneous power is the limiting value of the average power as the time interval Δt approaches zero. P = lim Δ t → 0 P a v g = lim Δ t → 0 Δ W Δ t = d W d t. In the case of constant power P, the amount of work performed during a period of duration t is given by: W = P t. In the context of energy conversion, it is more customary to use the symbol E rather than W. Power in mechanical systems is the combination of forces and movement. In particular, power is the product of a force on an object and the object's velocity, or the product of a torque on a shaft and the shaft's angular velocity.
Mechanical power is described as the time derivative of work. In mechanics, the work done by a force F on an object that travels along a curve C is given by the line integral: W C = ∫ C F ⋅ v d t = ∫ C F ⋅ d x, where x defines the path C and v is the velocity along this path. If the force F is derivable from a potential applying the gradi
In electronics, a digital-to-analog converter is a system that converts a digital signal into an analog signal. An analog-to-digital converter performs the reverse function. There are several DAC architectures. Digital-to-analog conversion can degrade a signal, so a DAC should be specified that has insignificant errors in terms of the application. DACs are used in music players to convert digital data streams into analog audio signals, they are used in televisions and mobile phones to convert digital video data into analog video signals which connect to the screen drivers to display monochrome or color images. These two applications use DACs at opposite ends of the frequency/resolution trade-off; the audio DAC is a low-frequency, high-resolution type while the video DAC is a high-frequency low- to medium-resolution type. Due to the complexity and the need for matched components, all but the most specialized DACs are implemented as integrated circuits. Discrete DACs would be high speed low resolution power hungry types, as used in military radar systems.
High speed test equipment sampling oscilloscopes, may use discrete DACs. A DAC converts an abstract finite-precision number into a physical quantity. In particular, DACs are used to convert finite-precision time series data to a continually varying physical signal. An ideal DAC converts the abstract numbers into a conceptual sequence of impulses that are processed by a reconstruction filter using some form of interpolation to fill in data between the impulses. A conventional practical DAC converts the numbers into a piecewise constant function made up of a sequence of rectangular functions, modeled with the zero-order hold. Other DAC methods produce a pulse-density modulated output that can be filtered to produce a smoothly varying signal; as per the Nyquist–Shannon sampling theorem, a DAC can reconstruct the original signal from the sampled data provided that its bandwidth meets certain requirements. Digital sampling introduces quantization error that manifests as low-level noise in the reconstructed signal.
DACs and ADCs are part of an enabling technology that has contributed to the digital revolution. To illustrate, consider a typical long-distance telephone call; the caller's voice is converted into an analog electrical signal by a microphone the analog signal is converted to a digital stream by an ADC. The digital stream is divided into network packets where it may be sent along with other digital data, not audio; the packets are received at the destination, but each packet may take a different route and may not arrive at the destination in the correct time order. The digital voice data is extracted from the packets and assembled into a digital data stream. A DAC converts this back into an analog electrical signal, which drives an audio amplifier, which in turn drives a loudspeaker, which produces sound. Most modern audio signals are stored in digital form and, in order to be heard through speakers, they must be converted into an analog signal. DACs are therefore found in CD players, digital music players, PC sound cards.
Specialist standalone DACs can be found in high-end hi-fi systems. These take the digital output of a compatible CD player or dedicated transport and convert the signal into an analog line-level output that can be fed into an amplifier to drive speakers. Similar digital-to-analog converters can be found in digital speakers such as USB speakers, in sound cards. In voice over IP applications, the source must first be digitized for transmission, so it undergoes conversion via an ADC, is reconstructed into analog using a DAC on the receiving party's end. Video sampling tends to work on a different scale altogether thanks to the nonlinear response both of cathode ray tubes and the human eye, using a "gamma curve" to provide an appearance of evenly distributed brightness steps across the display's full dynamic range - hence the need to use RAMDACs in computer video applications with deep enough colour resolution to make engineering a hardcoded value into the DAC for each output level of each channel impractical.
Given this inherent distortion, it is not unusual for a television or video projector to truthfully claim a linear contrast ratio of 1000:1 or greater, equivalent to 10 bits of audio precision though it may only accept signals with 8-bit precision and use an LCD panel that only represents 6 or 7 bits per channel. Video signals from a digital source, such as a computer, must be converted to analog form if they are to be displayed on an analog monitor; as of 2007, analog inputs were more used than digital, but this changed as flat panel displays with DVI and/or HDMI connections became more widespread. A video DAC is, incorporated in any digital video player with analog outputs; the DAC is integrated with some memory, which contains conversion tables for gamma correction and brightness, to make a device called a RAMDAC. A device, distantly related to the DAC is t
Atmospheric noise is radio noise caused by natural atmospheric processes lightning discharges in thunderstorms. On a worldwide scale, there are about 40 lightning flashes per second – ≈3.5 million lightning discharges per day. In 1925, AT&T Bell Laboratories started investigating the sources of noise in its transatlantic radio telephone service. Karl Jansky, a 22-year-old researcher, undertook the task. By 1930, a radio antenna for a wavelength of 14.6 meters was constructed in Holmdel, NJ, to measure the noise in all directions. Jansky recognized three sources of radio noise; the first source was local thunderstorms. The second source was weaker noise from more distant thunderstorms; the third source was a still weaker hiss that turned out to be galactic noise from the center of the Milky Way. Jansky's research made him the father of radio astronomy. Atmospheric noise is radio noise caused by natural atmospheric processes lightning discharges in thunderstorms, it is caused by cloud-to-ground flashes as the current is much stronger than that of cloud-to-cloud flashes.
On a worldwide scale, 3.5 million lightning flashes occur daily. This is about 40 lightning flashes per second; the sum of all these lightning flashes results in atmospheric noise. It can be observed, with a radio receiver, in the form of a combination of white noise and impulse noise; the power-sum varies with nearness of thunderstorm centers. Although lightning has a broad-spectrum emission, its noise power increases with decreasing frequency. Therefore, at low frequency and low frequency, atmospheric noise dominates, while at high frequency, man-made noise dominates in urban areas. From 1960s to 1980s, a worldwide effort was made to measure variations. Results have been documented in CCIR Report 322. CCIR 322 provided seasonal world maps showing the expected values of the atmospheric noise figure Fa at 1 MHz during four hour blocks of the day. Another set of charts relates the Fa at 1 MHz to other frequencies. CCIR Report 322 has been superseded by ITU P.372 publication. Atmospheric noise and variation is used to generate high quality random numbers.
Random numbers have interesting applications in the security domain. Radio atmospheric Singh, Big Bang: The Origin of the Universe, Harper Perennial, ISBN 978-0-00-716221-5 Spaulding, Arthur D..
Noise is unwanted sound judged to be unpleasant, loud or disruptive to hearing. From a physics standpoint, noise is indistinguishable from sound, as both are vibrations through a medium, such as air or water; the difference arises when the brain perceives a sound. Acoustic noise is any deliberate or unintended. In contrast, noise in electronics may not be audible to the human ear and may require instruments for detection. In audio engineering, noise can refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as a hiss; this signal noise is measured using A-weighting or ITU-R 468 weighting. In experimental sciences, noise can refer to any random fluctuations of data that hinders perception of a signal. Sound is measured based on the frequency of a sound wave. Amplitude measures; the energy in a sound wave is measured in decibels, the measure of loudness, or intensity of a sound. Decibels are expressed in a logarithmic scale. On the other hand, pitch is measured in hertz.
The main instrument to measure sounds in the air is the Sound Level Meter. There are many different varieties of instruments that are used to measure noise - Noise Dosimeters are used in occupational environments, noise monitors are used to measure environmental noise and noise pollution, smartphone-based sound level meter applications are being used to crowdsource and map recreational and community noise. A-weighting is applied to a sound spectrum to represent the sound that humans are capable of hearing at each frequency. Sound pressure is thus expressed in terms of dBA. 0 dBA is the softest level that a person can hear. Normal speaking voices are around 65 dBA. A rock concert can be about 120 dBA. In audio and broadcast systems, audio noise refers to the residual low-level sound, heard in quiet periods of program; this variation from the expected pure sound or silence can be caused by the audio recording equipment, the instrument, or ambient noise in the recording room. In audio engineering it can refer either to the acoustic noise from loudspeakers or to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as'hiss'.
This signal noise is measured using A-weighting or ITU-R 468 weighting Noise is generated deliberately and used as a test signal for audio recording and reproduction equipment. White noise is energy randomly spread across a wide frequency band containing all notes from high to low, it is called "white" noise as it is analogous to "white" light which contains all the colors of the visible spectrum. Environmental noise is the accumulation of all noise present in a specified environment; the principal sources of environmental noise are surface motor vehicles, aircraft and industrial sources. These noise sources expose millions of people to noise pollution that creates not only annoyance, but significant health consequences such as elevated incidence of hearing loss and cardiovascular disease. There are a variety of mitigation strategies and controls available to reduce sound levels including source intensity reduction, land-use planning strategies, noise barriers and sound baffles, time of day use regimens, vehicle operational controls and architectural acoustics design measures.
Certain geographic areas or specific occupations may be at a higher risk of being exposed to high levels of noise. Noise regulation includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government. Environmental noise is governed by laws and standards which set maximum recommended levels of noise for specific land uses, such as residential areas, areas of outstanding natural beauty, or schools; these standards specify measurement using a weighting filter, most A-weighting. In 1972, the Noise Control Act was passed to promote a healthy living environment for all Americans, where noise does not pose a threat to human health; this policy's main objectives were: establish coordination of research in the area of noise control, establish federal standards on noise emission for commercial products, promote public awareness about noise emission and reduction. The Quiet Communities Act of 1978 promotes noise control programs at the state and local level and developed a research program on noise control.
Both laws authorized the Environmental Protection Agency to study the effects of noise and evaluate regulations regarding noise control. The National Institute for Occupational Safety and Health provides recommendation on noise exposure in the workplace. In 1972, NIOSH published a document outlining recommended standards relating to the occupational exposure to noise, with the purpose of reducing the risk of developing permanent hearing loss related to exposure at work; this publication set the recommended exposure limit of noise in an occupation setting to 85 dBA for 8 hours using a 3-dB exchange rate. However, in 1973 the Occupational Safety and Health Administration maintained the requirement of an 8-hour average of 90 dBA; the following year, OSHA required employers to provide a hearing conservation program to workers exposed to 85 dBA average 8-hour workdays. The European Environment Agency regulates noise control and surveillance within the European Union
Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, urban planning through zoning codes, occupational noise control. Roadway noise and aircraft noise are the most pervasive sources of environmental noise. Social activities may generate noise levels that affect the health of populations residing in or occupying areas, both indoor and outdoor, near entertainment venues that feature amplified sounds and music that present significant challenges for effective noise mitigation strategies. Multiple techniques have been developed to address interior sound levels, many of which are encouraged by local building codes. In the best case of project designs, planners are encouraged to work with design engineers to examine trade-offs of roadway design and architectural design; these techniques include design of exterior walls, party walls, floor and ceiling assemblies.
Many of these techniques rely upon material science applications of constructing sound baffles or using sound-absorbing liners for interior spaces. Industrial noise control is a subset of interior architectural control of noise, with emphasis on specific methods of sound isolation from industrial machinery and for protection of workers at their task stations. Sound masking is the active addition of noise to reduce the annoyance of certain sounds. Organizations each have their own standards, recommendations/guidelines, directives for what levels of noise workers are permitted to be around before noise controls must be put into place. OSHA's requirements state that when workers are exposed to noise levels above 90 A-weighted decibels in 8-hour time-weighted averages, administrative controls and/or new engineering controls must be implemented in the workplace. OSHA requires that impulse noises and impact noises must be controlled to prevent these noises reaching past 140 dB peak sound pressure levels.
MSHA requires that administrative and/or engineering controls must be implemented in the workplace when miners are exposed to levels above 90 dBA TWA. If noise levels exceed 115 dBA, miners are required to wear hearing protection. MSHA, requires that noise levels be reduced below 115 dB TWA. Measuring noise levels for noise control decision making must integrate all noises from 90dBA to 140 dBA; the FRA recommends that worker exposure to noise should be reduced when their noise exposure exceeds 90 dBA for an 8-hour TWA. Noise measurements must integrate all noises, including intermittent, continuous and impulse noises between 80 dBA to 140 dBA; the DoD suggests that noise levels be controlled through engineering controls. The DoD requires that all steady-state noises be reduced to levels below 85 dBA and that impulse noises be reduced below 140 dB peak SPL. Time Weighted Average exposures are not considered for the DoD's requirements; the European Parliament and Council directive require noise levels to be reduced or eliminated using administrative and engineering controls.
This directive requires lower exposure action levels of 80 dBA for 8 hours with 135 dB peak SPL, along with upper exposure action levels of 85 dBA for 8 hours with 137 peak dBSPL. Exposure limits are 87 dBA for 8 hours with peak levels of 140 peak dBSPL. An effective model for noise control is the source and receiver model by Bolt and Ingard. Hazardous noise can be controlled by reducing the noise output at its source, minimizing the noise as it travels along a path to the listener, providing equipment to the listener or receiver to attenuate the noise. A variety of measures aim to reduce hazardous noise at its source. Programs such as Buy Quiet and the National Institute for Occupational Safety and Health Prevention through design promote research and design of quiet equipment and renovation and replacement of older hazardous equipment with modern technologies. Physical materials, such as foam, absorb sound and walls to provide a sound barrier that modifies existing systems that decrease hazardous noise at the source.
The principle of noise reduction through pathway modifications applies to the alteration of direct and indirect pathways for noise. Noise that travels across reflective surfaces, such as smooth floors, can be hazardous. Pathway alterations include sound dampening enclosures for loud equipment and isolation chambers from which workers can remotely control equipment while removed from noise; these methods prevent sound from traveling along a path to other listener. In the industrial or commercial setting, workers must comply with the appropriate Hearing conservation program. Administrative controls, such as the restriction of personnel in noisy areas, prevents unnecessary noise exposure. Personal protective equipment such as foam ear plugs or ear muffs to attenuate sound provide a last line of defense for the listener. Sound insulation: prevent the transmission of noise by the introduction of a mass barrier. Common materials have high-density properties such as brick, thick glass, metal etc. Sound absorption: a porous material which acts as a ‘noise sponge’ by converting the sound energy into heat within the material.
Common sound absorption materials include decoupled lead-based tiles, open cell foams and fiberglass Vibration damping: applicable for large vibrating surfaces. The damping mechanism works by extracting the vibration energy from the thin sheet and dissipating it as heat. A co