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Noise, which is often referred to as unwanted sound, is typically characterised
by the intensity, frequency, periodicity (continuous or intermittent) and duration
of sound. Sound is the result of pressure changes in the air caused by vibration.
Unwanted sound to some may be considered wanted sound by others, as in the case
of loud music.
More people are affected by noise exposure than any other environmental stressor.
However, because its associated health effects are not as life-threatening as those
for air, water and hazardous waste, noise has been on the bottom of most environmental
priority lists.
More recently, research has focused on noise as an auditory stressor that can produce
both direct and indirect health effects. The direct health effect known to be attributable
to noise is hearing loss (resulting from damage to the inner hair cells of the organ
of corti) with noise exposure higher than 90 decibels. There are several non-auditory
physiological effects of noise exposure including a possible increase in cardiovascular
disease from elevated blood pressure and physiological reactions involving the cardiovascular
endocrine system. In addition, community noise has been shown to adversely affect
sleep, communication, performance and behaviour, reading and memory acquisition,
and mental health.
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