The most common occupational health problem, especially in the manufacturing industries is industrial deafness. It is easy to identify, not very difficult to measure, and is in most cases, controllable.
Unfortunately, noise and hearing damage problems do not always receive the attention they deserve. Also, like so many occupational health hazards, noise is continually in the background. Individuals with noise-induced hearing loss may not become aware of the condition, which might have led to seeking hearing loss advice, until it is too late and becomes a severe and permanent handicap.
There is general agreement that daily average noise levels below 80 dB(A) are minimal, but noise levels above 90 dB(A) are hazardous. Individuals exposed between 85and 90 dB(A) need to be monitored because those who are more susceptible will develop a hearing impairment if they are exposed for sufficiently long durations.
Even noise levels as high as 130 to 140 dB(A) can be harmless if the duration is only a matter of a few milliseconds and there are no or few repetitions.
However, some individuals are more susceptible to noise exposure than others. Certain population studies indicate that males and fair-skinned people are more susceptible to noise induced hearing loss than females and dark-skinned people.
In most noisy workplaces, people communicate only minimally and have learned a system of gestures to accompany speech. Normal conversation in quite environments result in voice levels of about 50 to 55 dB(A). In noisy backgrounds, individuals will automatically raise their voices 5 or 6 dB(A) for every 10 dB(A) increase in noise level over approximately 45dB(A), so as to be heard over the background noise.
Research concerning the effects of noise on performance, has produced sufficient evidence to conclude that high levels of noise can adversely affect performance under certain circumstances.
Above levels of 130 or 140 dB(A) visual and motor effects can occur. Complex tasks, especially those involving simultaneous performance, can be disrupted at much lower levels, generally at 95 dB(A) and above. Particularly sensitive tasks can be affected at levels as low as80 to 85 dB(A). Intermittent and impulsive noise is more disruptive than continuous noise, especially when the noise bursts are unpredictable.
Adverse effects can also occur after the noise has ceased, and these often take the form of reduced tolerance for frustration. Finally, studies have shown that even fairly moderate levels of noise can raise anxiety and increase the risk of antisocial behaviour but ear protectors will usually lessen the adverse effects on performance.