The interaction of hearing loss and level-dependent hearing protection on speech recognition in noise

Objectives: To determine the effects of different control settings of level-dependent hearing protectors on speech recognition performance in interaction with hearing loss. Design: Controlled laboratory experiment with two level-dependent devices (Peltor (R) PowerCom Plus (TM) and Nacre QuietPro (TM)) in two military noises. Study sample: Word recognition scores were collected in protected and unprotected conditions for 45 participants grouped into four hearing profile categories ranging from within normal limits to moderate-to-severe hearing loss. Results: When the level-dependent mode was switched off to simulate conventional hearing protection, there were large differences across hearing profile categories regarding the effects of wearing the devices on speech recognition in noise; participants with normal hearing showed little effect while participants in the most hearing-impaired category showed large decrements in scores compared to unprotected listening. Activating the level-dependent mode of the devices produced large speech recognition benefits over the passive mode at both low and high gain pass-through settings. The category of participants with the most impaired hearing benefitted the most from the level-dependent mode. Conclusions: The findings indicate that level-dependent hearing protection circuitry can provide substantial benefits in speech recognition performance in noise, compared to conventional passive protection, for individuals covering a wide range of hearing losses.