Noise is best defined as unwanted sound; it can be a low background
sound or a loud agreeable or disagreeable sound.
Noise is measured in decibels, running from a virtually silent
0dB(A) up to 120dB (A) or more for the very noisiest of places. For very loud
short burst of sound a special scale is used to measure peak levels of
noise.
Although exposure to low or moderate levels of noise is unlikely to be very dangerous, exposure to loud noise over a prolonged period can impair hearing by damaging the fragile mechanism of the inner ear and destroying nerve cells.
Noise can cause hearing loss that can be temporary or permanent.
People often experience temporary deafness after leaving a noisy place,
although hearing recovers within a few hours. This is a sign that if you
continue to be exposed to the noise your hearing could be permanently damaged.
In some cases reduced hearing may result after only a few minutes or hours of
exposure to a loud noise. In these situations normal hearing will return after
a few hours away from the noise.
The effects of permanent hearing loss include
speech becoming muffled so that it is harder to distinguish similar sounding
words or to pick out a voice in a crowd.
Chronic hearing loss is caused by exposure over a gradual period of time and is sometimes referred to noise induced hearing loss, e.g. using a chainsaw over a period of time without using ear defenders. Because the hearing loss is gradual due to prolonged exposure it may only be when damaged caused by noise over the years combines with hearing loss due to ageing that people realise how deaf they have become. Hearing becomes muffled, conversations become difficult, difficulty using the phone or hearing the television.
Tinnitus is a
condition that causes an intermittent or permanent ringing, buzzing or humming
in the ears; this can cause severe concentration or sleep problems.
There are currently two action values set for workplace exposure
to noise. The lower exposure action value is a daily or weekly personal
noise exposure of 80 dB and a peak sound pressure of 135dB. At the lower action
values, employers must provide their employees with information, instruction
and training on the risks posed by noise and how to protect themselves. They
must also provide hearing protection for employees if they ask for it and
provide health surveillance if the worker is at particular risk.
The Upper exposure action value is a daily or weekly average
noise exposure of 85dB (A) and a peak sound pressure of 137dB. At the upper
exposure action values, employees must be provided with hearing checks and
employers must ensure hearing protection is worn by employees.
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