Relative ear protector performance in high vs low sound levels

The attenuation of one specific ear protector was determined for a group of five normal hearing subjects and a group of five hearing impaired subjects. The hearing impaired group yielded significantly less attentuation than the normal hearing group. Since the measuring sound intensity level was high for the hearing impaired listeners and low for the normal listeners, it appears that a threshold procedure using normal subjects, as presented in the American standard (ANSI S3.19-1974), may overestimate the actual attenuation of ear protectors in most noisy environments.