DETECTION OF WARBLE TONES IN WIDE-BAND NOISE WITH AND WITHOUT HEARINGPROTECTION DEVICES

Noise attenuation by linear hearing protection devices (HPDs) is consi dered to be independent of the environmental noise level. Linearity of HPDs is one of the basic assumptions underlying the Real Ear Attenuat ion at the Threshold (REAT) method of HPD testing, which utilizes quie t conditions. However, non-linear growth of masking al high intensity levels may result in the effects of HPDs on detection of speech and wa rning signals being different From those at high noise levels. The pur pose of this study was to determine if the non-linear growth of maskin g can affect detection of warble signals by persons using HPDs in wide band noise presented at the 100 dB(A) level. Audiometric thresholds of hearing of 10 listeners were measured under four experimental conditi ons: (1) noise off, HPDs off(condition C1); (2) noise off, HPDs on (co ndition C2); (3) noise on, HPDs on (condition C3); and (4) noise on, H PDs off (condition C4). The results of this study indicate that detect ion of signals by persons using HPDs in noise < 100dB(A) can be well p redicted From noise attenuation characteristics of HPDs measured in qu iet without the need for a correction factor accommodating non-linear growth of masking. This finding has implications for predicting the au dibility of warning signals in noise by persons wearing HPDs.