3. Effect of Noise on Man

All sounds that are distracting, annoying, or harmful to everyday activities such as work, rest, entertainment, study and so forth are regarded as noises. In fact, any sound judged by the recipient as undesirable can be considered as a noise.

Whether or not a sound is undesired by a person will depend on a number of factors, e.g.

(a) Loudness.

(b) Frequency.

(c) Continuity.

(d) Variation with time.

(e) Time of occurrence.

(f) Information content.

(g) Origin of the sound.

(h) Recipient's state of mind and temperament.

(i) Background noise level.

 

In general, the effects of noises are:

(a) Hearing Loss

Exposure to high noise levels causes hearing loss. This loss of hearing may be temporary, permanent, or a combination of both. Temporary hearing loss, also called Temporary Threshold Shift (TTS), results from exposure to short-term loud noises. As time passes, temporary hearing loss will disappear. However, if the human ear is not given the opportunity to recover, permanent hearing loss or Permanent Threshold Shift (PTS) will result because of the destruction of parts of the ear. Permanent hearing losses cannot be treated.

Figure 4 Permanent Threshold Shift (PTS) with Increasing Years of Exposure

Figure 5 Audiogram Showing Loss of Hearing with Age

(b) Other Health Effects

People living or working in noisy environments develop the habit of shouting; some are stressed and become irritable. There is evidence that noise can lead to psychiatric disorders. When human beings are exposed to high noise levels, the blood vessels constrict and muscles tense.

 

(c) Speech Interference & masking

One cannot effectively use speech communication in an environment in which the background noise level is too high. Sometimes, the masking of warning shouts by background noise is responsible for industrial accidents.

Nevertheless, a reasonable level of background noise is sometimes useful, e.g.

(i) the masking of speech so that speech privacy in large areas is maintained.

(ii) minimizing the effect of intruding noises.

(iii) maintaining the sanity of human beings: human beings cannot tolerate absolute silence in a perfect soundproof environment for any length of time.