Helena Joyce
Noise pollution, or sound pollution, is defined as the propagation of noise or sound with potentially harmful effects on humans, animals, and the environment. The unit used to measure noise pollution is the decibel (dB), which is a logarithmic unit that measures the loudness or sound pressure level (SPL) of a sound wave. SPL can be expressed as A-weighted decibels (dBA) or C-weighted decibels (dBC), with the former being the most commonly used metric. Noise pollution is commonly generated in industrial facilities, workplaces, and from transportation, construction, and urban activities. It can cause various negative health effects, including hearing loss, cardiovascular issues, stress, and sleep disturbances.
| Characteristics | Values |
|---|---|
| Unit of Sound Pollution | Decibel (dB) |
| Synonyms | Noise Pollution, Unwanted Sound |
| Sources | Machines, Transport, Propagation Systems, Industrial Facilities, Workplaces, Traffic, Construction, etc. |
| Effects | Hearing Loss, Cardiovascular Disorders, Hypertension, Stress, Tinnitus, Sleep Disturbances, etc. |
| Measurement Parameters | Pressure, Intensity, Frequency |
| Measurement Units | dB, Watts per meters-squared, Hertz (Hz) |
| Safe Exposure Limit | Below 80-85 dB (for 8-hour exposure) |
| Equivalent Units | dBA, dBC, Leq, LAeq, LAmax, etc. |
| Control Measures | Urban Planning, Noise Barriers, etc. |
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What You'll Learn
DeciBels (dB)
Sound is typically described in terms of loudness (amplitude) and pitch (frequency). Loudness, or sound pressure level, is what is being measured in decibels. Most people perceive a 6- to 10-dBA increase in an SPL reading as a doubling of "loudness". For example, an increase from 75 dB to 85 dB will sound roughly twice as loud.
The threshold at which noise becomes harmful to human health is 55 decibels, according to the World Health Organization (WHO). Exposure to sound levels above 81 dB has been shown to increase the chances of prehypertension and hypertension in a local population in Pakistan. Hearing loss does not usually occur at SPLs below 80 dBA, but most people exposed to more than 105 dBA will suffer from some degree of permanent hearing loss.
Noise pollution is unwanted or excessive sound that can have detrimental effects on human health, wildlife, and environmental quality. It is often generated in industrial facilities and other workplaces, as well as from road, rail, and air traffic, and construction activities. Noise pollution can also interfere with an animal's ability to attract a mate, communicate, navigate, find food, or avoid predators.
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Sound pressure level (SPL)
Sound pressure is the local deviation from the ambient air pressure caused by a sound wave. It is measured in pascals (Pa) and can be measured in the air using a microphone and in water using a hydrophone. The mathematical definition of sound pressure is the total pressure, which equals static pressure plus dynamic pressure. Sound pressure can also be described in terms of loudness (amplitude) and pitch (frequency).
The sound pressure level (SPL) is calculated by taking the ratio of the sound pressure to the reference level of sound pressure and then taking the logarithm (base 10) of that ratio, and then multiplying by 20. This gives the SPL in decibels (dB). For example, if the sound pressure is 200 µPa, then the ratio of the RMS sound pressure to the reference level of sound pressure is 10. Taking the logarithm (base 10) of this ratio gives 1, and multiplying by 20 gives an SPL of 20 dB.
SPL measurements can indicate the potential for hearing damage. Prolonged exposure to sound pressure levels above 85 dB can cause hearing damage, while levels above 120 dB can cause immediate and permanent hearing damage. Therefore, it is important to take appropriate measures to protect against loud noise exposure, such as wearing ear protection.
Noise pollution, or unwanted and excessive sound, can have detrimental effects on human health, wildlife, and environmental quality. It is often generated in industrial facilities, workplaces, and from traffic and construction. Noise pollution can cause hearing loss, raise blood pressure and pulse rates, and lead to stress, anxiety, and mental fatigue. It can also impact wildlife by interfering with their ability to communicate, navigate, and find food.
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Sound intensity
The unit of sound intensity is the decibel (dB). Decibels are used to calculate sound intensity and other physical quantities. Decibel is a tenth of the auxiliary unit of measurement Bel, named after Alexander Graham Bell. The sound pressure level is abbreviated with Lp (Level Pressure), and decibel with the letters dB. To calculate the sound intensity in decibels, a decibel meter is used. This is a measuring instrument that assesses sound levels by measuring sound pressure.
There are also subjective measures of sound intensity: the phon and the sone. The phon (or fon) refers to the sound intensity of 10-16 W/c2 at a frequency of 1,000 hertz. This corresponds to a sound pressure level of 2 x 10-10 bar. The sone is the psychoacoustic unit of measurement for the subjective loudness N of a sound event. At 1000 Hz sine, one sone corresponds to 40 phons or 40 decibels.
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Frequency
The unit of sound pollution is the decibel (dB), which is a logarithmic unit used to measure sound pressure level (SPL), or "loudness." An increase of 10 dB represents a ten-fold increase in sound intensity, while an increase of 20 dB represents a 100-fold increase, and so on.
Sound level meters are used to measure noise levels at different frequencies, typically using A- and C-weighted levels. The A-weighted decibel (dBA) scale is commonly used, with most people perceiving a 6- to 10-dBA increase as a doubling of loudness. The C-weighted (dBC) scale is often employed for impact noise levels, such as gunfire, and tends to be more accurate for the perceived loudness of low-frequency sounds.
In the context of noise pollution, frequency plays a crucial role in how sound is perceived and its potential impacts. Noise pollution, defined as unwanted or excessive sound, can have detrimental effects on human health, wildlife, and the environment. High noise levels have been linked to hearing loss, increased blood pressure and pulse rates, anxiety, and interference with sleep and communication. Additionally, noise pollution can affect wildlife, impacting their ability to communicate, navigate, and reproduce.
The frequency of sound waves helps distinguish anthropogenic noises from natural ones. Researchers also use different weights to account for noise frequency and intensity, as humans perceive sound at different loudness levels. For example, Z-weighting, or zero-weighting, represents noise levels without any frequency weights, while C-weighting is used for peak sound pressure or impulse noise, similar to loud, short-lived noises from machinery.
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A-weighted equivalent sound level (LAeq)
Sound pollution, or noise pollution, is defined as unwanted or excessive sound that can have harmful effects on human health, wildlife, and environmental quality. The unit used to measure noise pollution is Decibels (dB).
The A-weighted equivalent sound level, commonly represented as LAeq, is a measure of sound exposure that accounts for the varying sensitivity of the human ear to different frequencies. It is based on the equivalent continuous sound level (Leq), which quantifies the noise environment as a single value of sound level for any desired duration. The A-weighting is a frequency-weighting filter that approximates the frequency response of the human ear at typical conversational levels. It emphasizes frequencies that the human ear is most sensitive to and de-emphasizes those frequencies where our hearing is less sensitive. This makes LAeq particularly relevant for understanding human exposure to noise, as it represents noise in a way that aligns with our perceptual response.
The Leq equation represents the time average of the square of the sound pressure over a given time period. This average is then compared to the square of the reference pressure using a logarithm to convert the ratio to a decibel scale. The result is a single dB value that represents the equivalent continuous sound exposure. This value can be used to derive other acoustic indicators, such as LEX,8h for occupational noise or Rating Level for environmental noise.
LAeq can be calculated for different durations, such as 6, 8, 16, or 18 hours, depending on the specific application or context. It is an important metric for understanding the impact of noise on human health and welfare, as it provides a holistic understanding of the sound environment by averaging the entire audible frequency range.
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Frequently asked questions
The unit used to measure sound or noise pollution is Decibels (dB).
Sound pollution, or noise pollution, refers to unwanted or excessive sound that can have harmful effects on human health, wildlife, and environmental quality.
Sound pollution is commonly generated inside industrial facilities and some other workplaces. It can also come from road, rail, and air traffic, as well as construction activities, transportation, lawn care maintenance, electrical generators, and wind turbines.
