Life span and organ pathology in rats after life-long noise exposure

The role of ambient sound level in longevity, cause of death, and incidence of disease was investigated in rats. Two hundred twenty-seven rats (154 Sprague-Dawley (N), 73 spontaneously hypertensive Wistar (SH)), were housed in three sound isolated boxes and subjected to controlled acoustic milieus from approximately three months of age until their natural death. Thirty-nine of the N rats were kept as external controls in a regular animal room. In one of the boxes, no noise was introduced (control). In the other two, the rats were exposed, respectively, to a frequency-modulated, chopped noise with an equivalent level of 80 dB Leq and 100 dB Leq, ten hours daily. It was found that the SH animals had a shorter life span and a higher incidence of cardiovascular disease than the N rats but a lower rate of malignant tumors. No measurable effects on life span or total incidence of disease were seen. Minor differences in incidence of various disease entities were observed but were not consistent across groups. The results do not support the hypothesis that physical sound environment represents a significant cause of somatic disease.