Excessive exposure to noise can damage ()

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4. The health-harmful sound; the sources of it: the modes of evaluating and limiting of noise it out- and in-door ambient


  • -  Although some Presbyacusis 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 → some people's ears are more sensitive to loud sounds, especially at certain frequencies

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

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

  • -  A sound's loudness is measured in decibels (dB)

    • Normal conversation is about 60dB

    • In general, sounds above 85 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 (> 85dB):

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

      •   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): can be caused by a one-time exposure to loud sound as well as by repeated exposure to sounds at Various loudness levels over an extended period of time (more likely)

    • 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 detecting with hearing tests

      Methods for evaluation of loudness:

  • -  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

Source of sound

Sound level

Stun grenades


Jet engine at 1 m


Threshold of pain


Vuvuzela horn at 1 m


Traffic on a busy roadway at 10 m


Hearing damage (over long-term exposure, need Not be continuous)


Passenger car at 10 m


EPA – identified maximum to protect against Hearing loss and other disruptive effects from


noise, such as sleep disturbance, stress, learning Handheld electric mixer




Washing machine, dishwasher


Normal conversation at 1 m


Very calm room


  •  - The most common instruments used are the sound level meter (SLM), the integrating sound level meter (ISLM), and the noise dosimeter

  • -  Sound level meter (SML) = consists of a microphone, electronic circuits and a readout display

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

      •   These signals are then processed by the electronic circuitry of the instrument

      •   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 the 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

       Moreover, 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 → one solution is a noise dosimeter

  • -  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 industry where noise usually varies in duration and intensity, and where the person changes locations

  • -  Integrating Sound Level Meter: similar to the dosimeter

    • It 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

Type of Measurement

Appropriate Instruments (in order of preference)

Personal noise exposure

1) Dosimeter


3) SLM

Noise levels generated by a particular source

1) SLM


Noise survey

1) SLM


Impulse noise

1) Impulse SLM

Methods of limiting noise:

  • -  Isolation in residential areas (sound proof windows, isolating walls)

  • -  Wear hearing protection during work (when working in high-noise industries) or at home (when working w/ power tools)

  • -  Avoid firearm noise and recreational noise for long periods

  • -  Escape; allow your ears to rest in a quiet environment

  • -  Protect children

  • -  Have a medical examination by an ENT specialist and a hearing test

  • -  Outdoors:

    • Roadway noise can be reduced by the use of noise barriers, limitation of vehicle speeds, alteration of roadway surface texture, Limitation of heavy vehicles, use of traffic controls that smooth vehicle flow to reduce braking and acceleration, and tire Design

    • Aircraft noise can be reduced by using quieter jet engines

 Also by altering flight paths and time of day runway 

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