Effects on the inner and outer hair cells.

Scanning electron microscopy has improved the quality of the information obtained on morphological changes in the organ of Corti caused by noise exposure and the development of non-standard statistical methods has made accurate quantitative evaluation of these morphological changes possible. Many different types of hair cell damage were observed in noise-exposed cochleas, and the changes found in the inner and outer hair cells were found to differ considerably. Both analysis of impulse noise and continuous noise gave different results when applied to the inner hair cells as compared to when applied to the outer hair cells. However, of the outer hair cell rows the outermost was most frequently damaged by both impulse noise and continuous noise. The results of this investigation support previous suggestions that the inner and outer hair cell rows should be evaluated separately in experimental research.