Abstract
Functional and morphological changes of the cochlea induced by the white noise of 100 dB SPL were studied using auditory brain-stem response (ABR) and scanning electron microscopy (SEM) in guinea pigs. Twenty guinea pigs with normal Preyer's reflex, weighing about 300g were used for this investigation. They were exposed to white noise of 100 dB SPL for one hour in six (Group A), three hours in six (Group B) and five hours in eight (Group C) experimental animals. ABR and SEM were performed just after and one week after the noise exposure.
A slight and temporary prolongation of the latency of AP (N1) was detected but no morphological changes were observed in Group A. A moderate prolongation of the latency and swelling of supporting cells were observed but these changes returned to the preexposure condition in Group B. Severe and irreversible prolongation of the latency or no response were detected and marked disturbances of surface ultrastructure of hair cells (especially outer hair cells) were observed in the lower half of the third turn in Group C.
The power spectrum analysis of the noise revealed many echos of various cycles and morphological changes of hair cells were most remarkable in the region corresponded to the peaks of these spectra.
