Hearing protection devices (HPDs) are essential safety equipment for workers in noisy settings but can also degrade auditory perception. Reports have suggested HPDs reduce speech intelligibility at low levels, or improve intelligibility at higher levels, while others find no effect for normal-hearing listeners. Here, we assess HPD use on speech intelligibility in normal hearing subjects, and compare behavioral performance to acoustical predictions with the Speech Intelligibility Index (SII). 127 audiometrically normal-hearing young adults across two sites were administered the Quick Speech-in-Noise (QuickSIN) and Modified Rhyme Test (MRT). Subject were tested under open-ear and 6 HPD listening conditions, while the signal-to-noise ratio (SNR) was varied (QuickSIN: multi-talker babble; MRT: pink noise), and performance characterized as percentage of words correctly identified. SII was calculated from recordings made with an acoustic manikin (GRAS 45CB). Subject performance was comparable to open ear for most HPDs, except performance was somewhat degraded with a high-attenuation earplug (both tasks) and improved (MRT only) with an active muff. Results are predicted by SII when HRTF, insertion loss, and speech spectrum are accounted for. These results suggest robust speech perception across most listening conditions, but emphasize the importance of appropriate HPD selection for applications where communication is critical.
Butler et al. (2025) studied this question.