Frequency Selectivity in Noise-Damaged Cochleas

Abstract

Measures of auditory threshold and masked threshold were obtained at six audiometric test frequencies along with co-chleograms on a total population of 363 noise-exposed chinchillas. Seventy animals were chosen from this sample and were separated into five relatively homogeneous groups based upon the amount of permanent threshold shift and sensory cell losses the animals incurred. Tuning curve (TC) metrics were compared to the mean preexposure TC metrics for each group and to the reference preexposure TC metrics obtained from the sample of 363 animals. These data show that in animals with relatively little hearing loss changes in TC metrics can provide evidence for noise-induced sensory cell losses and that the low frequency slope of the TC is a sensitive index of trauma.

Key Words:

• Tuning curve
• Sensory cell loss
• Threshold shift
• Evoked potentials
• Frequency selectivity