Recommended criteria for evaluating the effectiveness of hearing conservation programs

Abstract
Hearing level data from several North Carolina industrial populations is analyzed. The analysis considered several different test retest criteria as well as changes in hearing levels with time at different testing frequencies. The findings demonstrate the necessity for subdividing the populations by race and sex. A characteristic of programs that are classified as acceptable is a significant improvement over the first four to six years of testing in the mean hearing levels (the learning curve) at 3, 4 and 6 kHz with respect to the baseline hearing test. A significant correlation is established between the change in the mean hearing level at 4 kHz and a test retest criterion defined as a shift in mean hearing level equal to or greater than 15 dB at any frequency tested in either ear.