Practice effects in industrial hearing screening.

Abstract

Two samples of employees were drawn at random from the total population of approximately 12,000 employees in one large company. The base-line audiograms and two subsequent annual retests were studies on a sample of 118 employees to determine whether the mean threshold values improved with subsequent years of testing. In addition, the audiometric earphones were reversed so that the right ear was tested first on an automatic audiometer, followed by the left ear on a different sample of 400 employees in an effort to determine whether there is a significant difference between the first and second ear tested. Results indicate that subsequent retests do not show significant improvements. It is possible, however, the small improvements of 1 or 2 dB reported by other investigators over several years of testing may not be seen when mean values are used on populations of this size. Of more importance, however, was the fact that a consistent and significant difference was seen between the first and second ear tested, with the first ear tested showing the poorer threshold. When earphones were reversed, the left or previously poorer ear, showed better thresholds than the right in the low- and midfrequencies. The right ear continued to show better thresholds in the high frequencies, regardless of which ear was tested first.