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

Abstract

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^® PowerCom Plus™ and Nacre QuietPro^®) 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.

Key Words::

• Hearing loss
• hearing protection
• speech recognition
• noise

Acknowledgements

Work based on Defence R&D Canada Contractor Report DRDC Toronto CR-2011-101. Part of this study was presented at the 21st International Congress on Acoustics in Montréal, Canada (2–7 June, 2013) and the 39th Annual Conference of the National Hearing Conservation Association in Las Vegas, USA (13–15 March, 2014).

Declaration of interests: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.