Perceptive Deafness and Presbycusis

Noise-Imduced Deafness

Abstract

The changes in hearing after patients with noiseinduced deafness have left their jobs at noisy working places were studied and a follow-up study showed the following results.
1) While persons were working at noisy places, their hearing under a noisy environment was deteriorated rapidly and relatively early, between 5 and 15 years, and thereafter it remained unchanged or deteriorated very slowly. This slow deterioration was almost consistent with physiological presbycusis. In the high frequency region, hearing deteriorated in those who were exposed to high pitch noise.
2) According to the results of a follow-up of more than 10 year's duration after leaving from their jobs at noisy places, hearing was deteriorated in almost the same manner as in presbycusis at 250Hz to 2000Hz. At 4kHz and 8kHz, however, the deterioration was slow compared with presbycusis, probably because hearing was already deteriorated considerably at the time of leaving from their jobs.
3) The results of a follow-up of more than 5 year's duration were almost the same as the results of the aforementioned 10 year's follow-up. In the low to middle frequencies, however, hearing was deteriorated markedly compared to presbycusis in some cases.
On the basis of the results, pathophysiology of the inner ear was discussed in reference to noiseinduced deafness and presbycusis.