Speech-in-noise recognition during hearing protector use: Human performance and acoustic prediction

Area of Science:

• Audiology and Acoustics
• Occupational Safety and Health

Background:

• Hearing protection devices (HPDs) are crucial for noise exposure mitigation in occupational settings.
• The impact of HPDs on speech intelligibility remains debated, with varying effects reported for normal-hearing individuals.

Purpose of the Study:

• To evaluate the effects of various HPDs on speech intelligibility across different signal-to-noise ratios (SNRs).
• To compare behavioral performance with acoustical predictions using the Speech Intelligibility Index (SII) and a spatially-informed version (sSII).

Main Methods:

• 124 normal-hearing subjects participated in speech intelligibility tests (Quick Speech-In-Noise and Modified Rhyme Test) under open-ear and six HPD conditions.
• Acoustical predictions were made using SII and sSII, incorporating head-related transfer functions (HRTFs) for spatial accuracy.

Main Results:

• Most HPDs yielded speech intelligibility comparable to open-ear conditions.
• A high-insertion-loss passive earplug significantly degraded performance, while electronic earmuffs showed a modest improvement in one test.
• The spatially-informed sSII model demonstrated a substantially higher predictive accuracy (R²=0.497) compared to the standard SII (R²=0.212).

Conclusions:

• Speech perception is generally well-maintained with most commonly used HPDs.
• Incorporating spatial acoustic information significantly enhances the prediction of speech intelligibility with HPDs.
• Careful selection of HPDs is important, and advanced acoustical modeling improves understanding of speech perception in noise.