Impulse noise of different durations.

This paper describes a comparison between auditory threshold elevations and morphological cochlear changes evaluated with scanning electron microscopy in order to identify cochlear defects in guinea pigs exposed to impulse noise of varying durations. There was a significant difference in the auditory threshold shifts between animals exposed for 3 and 12 hours. Hair cell loss is generally used as a morphological correlate to noise-induced hearing loss. Minor stereocilia changes, quantified with non-standard statistical methods have been used as a complement. Morphologically, it was not possible to separate cochleas exposed to impulse noise for 3 and 12 hours when only lost hair cells were evaluated. Quantitative evaluation of subtle morphological changes are valuable in the correlation of noise-induced hearing loss with morphologic changes.