The influence of wearing hearing protectors on the detection of seven railway warning signals in noise was evaluated by comparisons of the masked thresholds measured with and without hearing protectors, out of a total of eighty listeners. The results show that wearing the HPDs improves the audibility for normal hearing listeners whereas it tends to impede the audibility for hearing impaired listeners. Moreover, the impediments greatly depend on the warning signal acoustical characteristics. Statistical analyses were performed in order to propose a criterion for hearing impaired listeners that guarantees their security when wearing hearing protectors. If we do not consider one given high-pitched signal that is not suitable as a warning signal, the conclusion is that the security is assured when the average absolute hearing threshold (average at 500, 1000 and 2000 Hz on the best ear) of the listeners remains lower than 30 dB Hearing Level.

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