The cubic distortion product otoacoustic emissions from the normal and noise-damaged chinchilla cochlea.

A normative study of the cubic distortion product emissions from 104 monaural and binaural chinchillas was undertaken to establish criteria upon which noise exposed animals could be evaluated. From this normative group, 47 randomly selected chinchillas were exposed to various high level (150-, 155-, and 160-db peak SPL) impulse noises. Auditory evoked potentials and cubic distortion product otoacoustic emissions were measured on each animal pre- and post-exposure and related to the sensory cell populations 30 days post-exposure. Both group mean and individual animal data indicated that the distortion product emissions were more sensitive, frequency-specific indices of noise-induced cochlear effects than pure-tone threshold measures. This was particularly evident near the threshold for noise-induced damage to the outer hair cell system.