Noise Pollution: Health Impacts, Measurement, and Control

Posted on Sep 3, 2025 in Other subjects

Harmful Noise: Sources, Evaluation, and Control

Background on Noise Pollution

• Although some presbycusis may occur naturally with age, in many developed nations the cumulative impact of noise is sufficient to impair the hearing of a large fraction of the population over the course of a lifetime.

• Elevated workplace or other noise can cause hearing impairment, hypertension, ischemic heart disease, annoyance, and sleep disturbance.

• Changes in the immune system and birth defects have been attributed to noise exposure.

• The effects of noise on hearing vary among people; individual sensitivity to loud sounds differs, especially at certain frequencies.

• The frequency of a sound determines how low or high a tone is.

• However, any sound that is loud enough and lasts long enough can damage hearing and lead to hearing loss.

Measuring Sound Loudness: Decibels (dB)

• A sound’s loudness is measured in decibels (dB).

  • Normal conversation is about 60 dB.

  • In general, sounds above 85 dB are harmful, depending on how long and how often you are exposed to them and whether you wear hearing protection, such as earplugs or earmuffs.

  • The louder the sound, the shorter the allowable exposure time.

  • Sources of loud noises (> 85 dB):

    • Heavy traffic, noisy restaurant, power lawn mower: 80-89 dB

    • Subway, shouted conversation: 90-95 dB

    • Motorcycle, boom box: 96-100 dB

    • School dance: 101-105 dB

    • Sports crowd, rock concert, loud symphony: 120-129 dB

    • Gunshot, siren at 100 feet: 140 dB

• A sound may be harmful if:

  • You have difficulty talking or hearing others talk over the sound.

  • The sound makes your ears hurt.

  • Your ears are ringing after hearing the sound.

  • Other sounds seem muffled after you leave an area where there’s loud sound.

• Noise-Induced Hearing Loss (NIHL)

  Noise-induced hearing loss (NIHL) can be caused by a single exposure to loud sound or, more commonly, by repeated exposure to sounds at various loudness levels over an extended period.

  • Symptoms of NIHL increase gradually over a period of continuous exposure; sounds become distorted or muffled, and it may be difficult to understand speech.

  • Sometimes the individual may not be aware of the hearing loss, but it can be detected with hearing tests.

Evaluating Noise Levels

• The sound pressure level is measured to determine noise exposures.

• Various instruments and techniques may be used.

• The choice depends on the workplace noise and the information needed.

Common Noise Measurement Instruments

• The most common instruments used are the Sound Level Meter (SLM), the Integrating Sound Level Meter (ISLM), and the Noise Dosimeter.

• Sound Level Meter (SLM)

  An SLM consists of a microphone, electronic circuits, and a readout display.

  • The microphone detects small air pressure variations associated with sound and converts them into electrical signals.

    • These signals are then processed by the instrument’s electronic circuitry.

    • The readout displays the sound level in decibels.

    • The SLM takes the sound pressure level at one instant in a particular location.

  • To take measurements, the SLM is held at arm’s length at ear height for those exposed to the noise.

  • A standard SLM takes only instantaneous noise measurements. This is sufficient in workplaces with continuous noise levels.

  • However, in workplaces with impulse, intermittent, or variable noise levels, the SLM makes it difficult to determine a person’s average exposure to noise over a work shift. Therefore, a noise dosimeter is often a better solution.

• Noise Dosimeter

  • A noise dosimeter is a small, light device that clips to a person’s belt with a small microphone that fastens to the person’s collar, close to an ear.

  • The dosimeter stores the noise level information and carries out an averaging process.

  • It is useful in industries where noise usually varies in duration and intensity, and where the person changes locations.

• Integrating Sound Level Meter (ISLM)

  Similar to the dosimeter, an ISLM determines equivalent sound levels over a measurement period.

  • The major difference is that an ISLM does not provide personal exposures because it is hand-held like the SLM and is not worn.

Methods for Noise Control and Prevention

• Isolation in residential areas: Utilize soundproof windows and isolating walls.

• Wear hearing protection: Essential during work in high-noise industries or at home when using power tools.

• Avoid prolonged exposure to firearm noise and recreational noise.

• Take breaks: Allow your ears to rest in a quiet environment.

• Protect children from excessive noise.

• Seek medical advice: Have a medical examination by an ENT specialist and a hearing test if concerns arise.

• Outdoor Noise Reduction Strategies

  • Roadway noise can be reduced by using noise barriers, limiting vehicle speeds, altering roadway surface texture, limiting heavy vehicles, using traffic controls that smooth vehicle flow to reduce braking and acceleration, and optimizing tire design.

  • Aircraft noise can be reduced by using quieter jet engines, altering flight paths, and adjusting times of day for runway use.