Physiological aspects of the effects of sound on man and animals.

A review of some short-term and long-term physiological effects of sound on non-auditory body functions is given. It is pointed out that the short-term effects depend closely on the acoustic properties of the sound. Habituation is rapid for steady signals but slow for interrupted ones. Irrelevant, meaningless sound, presented to rats over their life-time in such a way as to simulate an industrial acoustic environment, did not affect blood pressure, life-span or morbidity incidence. As far as the injurious effect of sound on the inner ear is concerned, it was shown that spontaneously hypertensive rats were considerably more susceptible to such impairment than were normotensive ones. Hence sound does not produce hypertension, but susceptibility to ear injury may be greater in hypertensive individuals. The protential role which individual variability in physiological properties of the sound conduction system might play for the observed individual variability in noise-induced hearing loss is also discussed.