Hair cell damage in the inner ear of the guinea pig due to noise in a workshop.

Guinea pigs were exposed to noise in various workshops at a shipyard. The equivalent sound level ranged from 87 to 90 dB(A) and the exposure time was 30 days of 8 hours. The numbers of lost outer hair cells were greater than in control animals, thus establishing a relation between the number of lost hair cells and the total noise dose. A comparison between the results obtained here and results obtained in laboratory experiments shows that although many physical sound parameters may be identical, the effect on the hair cells can be quite different. In particular, the total noise dose is not a parameter which can be directly related to hair cell loss. The most probable explanation for the difference in damage between the laboratory and workshop animals seems to be the rest periods of 16 hours between each of the 8-hour exposure periods.