Speech recognition in noise under hearing protection: A computational study of the combined effects of hearing loss and hearing protector attenuation

Abstract

Objective: To investigate the effects of hearing protection on speech recognition in noise. Design: Computational study using a speech recognition model that was previously empirically validated. Study sample: Recognition scores were calculated in unprotected and protected conditions for four sets of hearing protector attenuation functions in two different noises, for three simulated hearing profiles illustrative of those anticipated in the noisy workplace. Results: For a normal-hearing profile, recognition scores were not sensitive to the slope of the attenuation function and the overall amount of noise reduction, but protected conditions provided a small but consistent 7–12% benefit compared to unprotected listening. For profiles simulating hearing loss, recognition scores were much more sensitive to the attenuation function. Substantial drops of 30% or more were found compared to unprotected listening in some conditions of steep attenuation slopes and large noise reductions. Attenuation functions modelled from real hearing protectors with nearly-flat attenuation yielded a benefit compared to unprotected listening for all hearing profiles studied. These findings were true in both noises. Conclusions: Limiting the slope of the hearing protector attenuation function and/or the overall amount of noise reduction is useful and warranted for workers with hearing loss to prevent adverse effects on speech recognition.

Key Words:

• Hearing protection
• hearing loss
• speech recognition
• noise

Acknowledgements

The careful review and helpful comments by Cameron Fackler that enhanced the clarity of the manuscript, are appreciated.

Declaration of interest

The first author reports no conflicts of interest. The second author is employed at 3M, the manufacturer of 3M™ Hi-Fi™ Earplugs. The authors alone are responsible for the content and writing of the paper. Note that Musicians Earplugs is a trademark of Etymotic Research, Inc. 3M and Hi-Fi are trademarks of 3M Company.