Action Potential Threshold Elevation in the Guinea-Pig as a Function of Impact Noise Exposure Energy

Abstract

Eighteen groups of guinea pigs were exposed to a simulated impact noise for periods of 1.5-24 h. The peak level was kept constant at 131.5 dB and the repetition rate was varied to give seven different equivalent levels (L_eq) between 96 and 117 dB. The auditory thresholds were assessed by electrocochleography after 1 month and compared with those of a control group. Significant damage occurred even at the lowest exposure energy used. When the total exposure energy was expressed on a decibel scale, the threshold elevation (1-10 kHz) increased 1.07 dB for each decibel increase in the exposure energy, regardless of the combination of L_cq and exposure time. The results of the study thus support the equal-energy hypothesis under these conditions.

Key Words:

• Impact noise
• Threshold shift
• Equal-energy hypothesis