[Asymptotic points of functional and morphological damages produced by acoustic trauma in guinea pig cochleas]

Experimental animals were exposed to 3 kHz pure tone with an intensity of 110 dB (A) for from 10 minutes to 5 days. Structural damages were assessed by surface specimen technique and functional damages estimated by the N1 threshold audiogram. The asymptote of auditory threshold shift was reached after 2 hours of exposure. Corresponding to it, there was an asymptote of morphological damage as well. The existence of asymptote doesn't mean free from further damage in spite of continuous exposure. The maximum N1 threshold occurred at a frequency higher than the exposed frequency. However, the maximum morphological damage was observed in a region of the organ of Corti corresponding to the exposed frequency.