What is Noise Pollution?

Noise Pollution: What it is, causes, effects and prevention

Noise pollution is defined as unwanted or excessive sound that can have harmful effects on human health and environmental quality. Noise pollution is a type of environmental pollution and it is commonly generated in many industrial facilities and some workplaces, as well as from road, rail, and air traffic and outdoor construction activities.

Noise pollution is most prevalent in densely populated areas where urbanization and industrialization are on the rise. For example, we can cite the noise pollution caused by construction activities in big cities due to urban renewal.

Noise can encompass all recipient media as a source of origin and propagation. However, noise that directly harms humans is more often associated with air as a recipient medium. Noise, which results from the disturbance of an environmental value, affects the perception of other environmental values and becomes a health-disrupting factor. Therefore, noise is considered an environmental and health problem today.

In developed countries, the problem of noise pollution, which has emerged with the development of industry and technology, is one of the important environmental issues of our time, but it is a less known type of pollution in our country.

Noise pollution is a type of pollution that negatively affects people’s hearing health and perception, disrupts their physiological and psychological balance, reduces their internal performance, and changes the quality of the environment and its serenity.

A series of vibrations initiated by a vibrating object is called sound. Vibrational motion is required for sound to occur. Sound waves are vibrations of air molecules carried from a noise source to the ear. Sound is typically characterized in terms of wave amplitude (loudness) and frequency (pitch). Sound amplitude (sound pressure level or SPL) is measured in decibels (dB).

Sounds must reach a certain level to be considered noise.

The human ear can perceive sounds ranging from approximately 0 dB (hearing threshold) to about 140 dB, and sounds between 120 dB and 140 dB can cause pain (pain threshold). The ambient SPL in a library is approximately 35 dB, while inside a moving bus or subway train, it is roughly 85 dB; building construction activities can produce SPLs of up to 105 dB at the source. SPLs decrease with distance from the source.

The rate at which sound energy is transmitted, called sound intensity, is proportional to the square of the SPL. Due to the logarithmic nature of the decibel scale, a 10 dB increase represents a tenfold increase in sound intensity, a 20 dB increase represents a 100-fold increase in intensity, and a 30 dB increase represents a 1,000-fold increase. When sound intensity doubles, SPL only increases by 3 dB.

For example, if a construction drill produces a noise level of approximately 90 dB, two identical drills working side by side will produce a noise level of 93 dB. On the other hand, when two different sounds with a difference of 15 dB or more are combined, the weaker sound is masked (or drowned out) by the louder sound. For example, if a dozer on a construction site is producing 95 dB and a drill is producing 80 dB, the combined SPL will be measured as 95 dB, and the less intense noise from the compressor will not be noticed.

Measurement and Perception of Noise

The precise measurement and scientific description of sound levels are different from most subjective human perceptions and opinions about sound. People’s subjective responses to noise depend on both the sound spectrum and sound intensity. Typically, normal hearing individuals perceive high-frequency sounds as higher in volume than low-frequency sounds of the same amplitude. Therefore, electronic sound level meters used to measure noise levels take into account changes in perceived sound loudness with changes in sound frequency.

The frequency filters in meters serve to match meter readings to human hearing sensitivity and the relative loudness of various sounds. For example, an A-weighted filter is commonly used to measure the community’s noise because it takes into account the changes in perceived sound loudness with sound frequency. Measurements made with this filter are expressed as A-weighted decibels or dBA.

Most people perceive an increase of 6-10 dBA in SPL reading as doubling the “loudness” of the sound and describe it as such. Another system, the C-weighted (dBC) scale, tends to be more accurate for sounds with low-frequency components and impulsive sounds, such as gunshot noises, which have a different perceived loudness compared to dBA.

Noise levels often vary over time, so noise measurement data are reported as time-averaged values to represent overall noise levels. There are several ways to do this.

For example, the results of a series of repeated sound level measurements can be reported as L90 = 75 dBA, which means that 90% of the levels are equal to or higher than 75 dBA. Another unit called equivalent sound levels (Leq) can be used to express the average SPL over any interest period, such as an eight-hour workday. (Leq is a logarithmic average rather than an arithmetic average, so it tends to be dominated by noisy events.)

Day-night sound level (DNL or Ldn) is another unit that explains that people are more sensitive to noise at night, so a penalty of 10 dBA is added to SPL values measured between 10:00 PM and 7:00 AM.

DNL measurements are very useful for defining the community’s exposure to aircraft noise, for example.

Causes of Noise Pollution

Noise pollution, the unwanted and disruptive sound in our environment, is primarily driven by various human activities and factors. The following are the key contributors to this pervasive issue:

1. Urbanization and Industrialization

The rapid growth of urban areas and expanding industrial facilities contribute significantly to noise pollution. These settings often involve various activities and machinery that generate high levels of noise.

2. Transportation Systems

Road, rail, and air traffic are major contributors to noise pollution, especially in densely populated urban regions with heavy traffic congestion. The continuous movement and operation of vehicles and aircraft emit substantial noise.

3. Outdoor Construction Activities

Construction sites, with their use of heavy machinery and equipment, generate considerable noise pollution. These activities disrupt the peace and quiet of both urban and rural environments.

4. Technological Advancements

The advancement of technology has led to the widespread use of noisy equipment and devices, such as power tools, loudspeakers, and motorized vehicles, further exacerbating noise pollution.

5. Human Activities

Everyday activities, such as social gatherings, entertainment events, and recreational activities, also contribute to noise pollution when they occur at high volumes or in densely populated areas.

6. Natural Phenomena

Although less common, natural phenomena like thunderstorms and volcanic eruptions can produce loud noises that temporarily contribute to noise pollution.

Effects of Noise and Coping Strategies

Noise is more than just an unwanted condition. At certain levels and durations of exposure, it can cause physical damage to the eardrum and the delicate hair cells of the inner ear, leading to temporary or permanent hearing loss. Hearing loss typically does not occur at SPLs below 80 dBA (eight-hour exposure levels are kept below 85 dBA), but most people exposed to levels exceeding 105 dBA consecutively will experience some degree of permanent hearing loss.

In addition to causing hearing loss, excessive noise exposure can also increase blood pressure and heart rate, lead to irritability, anxiety, and mental fatigue, and interfere with sleep, relaxation, and personal communication. Therefore, noise pollution control is important in the workplace and in the community.

Effects of Noise Pollution on Human Health

1. Temporary and permanent hearing impairments
2. Behavioral problems, excessive irritability, stress, sleep disturbances
3. Reduced work productivity, impaired movements, concentration disorders
4. Increased blood pressure, respiratory system effects, circulatory system disorders, changes in heart rhythm, sudden reflex responses

Noise control regulations and laws enacted at the local, regional, and national levels can be effective in reducing the adverse effects of noise pollution.

Environmental and industrial noise in the United States is regulated under the Occupational Safety and Health Act of 1970 and the Noise Control Act of 1972. These laws empower the Occupational Safety and Health Administration to establish industrial noise criteria to ensure compliance with intensity limits.

Indoor noise criteria were summarized with three sets of features obtained by collecting subjective judgments from a wide sample of people in various specific situations. These criteria have become curves known as noise criteria (NC) and preferred noise criteria (PNC) curves, providing design targets for noise levels in various situations. The goal of the NC curves developed in 1957 is to provide a comfortable working or living environment by specifying the maximum allowable noise level in octave bands across the entire sound spectrum.

All 11 curves specify noise criteria for a wide variety of situations. The PNC curves developed in 1971 add limits for low-frequency rumble and high-frequency hiss, making them preferable to the old NC standard. These criteria summarized in the curves provide design objectives for noise levels in various situations. Some of the characteristics of a work or living environment are compatible with an appropriate PNC curve, and sound-absorbing materials can be activated as needed to meet the required standards if the sound level exceeds PNC limits.

Methods to Prevent Noise Pollution

In enclosed spaces, low noise levels can be achieved by using additional absorbing materials such as heavy curtains or sound-absorbing tiles. Low-level detectable noise levels can be distracting or important in situations where unwanted sounds may be distracting or where conversations in adjacent offices and reception areas may require privacy, masking can be used to mask unwanted sounds.

A small white noise source, such as static or flowing air, held in the same way as headphones on the ears, can mask conversation sounds from neighboring rooms without disturbing the ears of nearby workers. These devices are commonly used in doctors’ offices and other professionals’ offices.

Another technique to reduce personal noise levels is to use hearing protectors, such as earmuffs worn over the ears or earplugs inserted into the ear canal.

Using headphone-type hearing protectors available in the market, a decrease of more than 30 dB between 100 Hz and frequencies typically occurs at 100 Hz, allowing for protection of the ears against high-intensity noise.

Outdoor noise limits are also important for human comfort. Standard home construction will provide some protection from external noise if the home meets minimum construction standards and if the external noise level is within acceptable limits. These limits are usually specified for certain periods of the day – for example, during daylight hours, evening hours, and nighttime sleep hours. Due to temperature changes at night that cause atmospheric refraction, relatively high noise levels can be caused by a highway, airport, or railway far away.

An interesting technique for controlling road noise is the installation of noise barriers alongside the road and the separation of the road from adjacent residential areas. The effectiveness of such barriers is limited, particularly in the low-frequency components that dominate in road noise, as it is important to break the sound at the source or observer (preferably at the source).

Source:Brittanica