Speech recognition in noise before and after a work-day's noise exposure.

A common complaint after a work-shift in high noise levels is fatigue, in the sense that listening to other people's spoken messages requires more effort than when well rested. The purpose of this study was to examine if this could be verified as reduced speech recognition in noise due to auditory fatigue. Speech recognition in noise, using low-redundancy sentence material, as well as pure-tone hearing thresholds were tested on 13 subjects at the beginning and end of a 7-8 hours work-shift with equivalent noise levels in the range 78-90 dBA as measured by personal noise dose meters. Seven of the test subjects wore hearing protectors during work while six did not. No significant shift in mean values from the beginning of the work-shift to its end could be found, neither in speech recognition in noise nor in hearing thresholds for pure tones and neither for those wearing hearing protectors nor for those without.