Effect of wearing hearing protectors on the audibility of railway warning signals for hearing-impaired listeners — an experimental study

摘要

In order to evaluate the effect of wearing hearing protector devices (HPDs) on the audibility of railway warning signals, masked thresholds measurements were performed in the laboratory with and without wearing the HPDs. Seven railway warning signals and two HPDs (custom molded earplugs and a passive earmuff) were tested on normal-hearing (NH, N=11) and hearing-impaired (HI, N=60) listeners with various hearing loss profiles. The results show that for NH subjects, the audibility is generally improved when wearing the HPDs (i.e. the protected thresholds are lower than the unprotected thresholds). On the contrary, for HI subjects, the protected thresholds are higher than the unprotected thresholds and this detrimental effect of HPDs tends to increase with increasing hearing loss. To guarantee the security of HI workers, it was considered that their protected thresholds should not be higher than the unprotected thresholds of the NH subjects. Based on this statement, the results show that the security of HI workers is guaranteed up to around 25 d B of hearing loss (dB HL), in average at 500,1000 and 2000 Hz in the best ear.