Most Comfortable Listening Level and Speech Attenuation by Hearing Protectors

Area of Science:

• Audiology
• Occupational Health
• Acoustics

Background:

• Hearing protection devices (HPDs) reduce environmental noise but can also attenuate crucial sounds like speech and warning signals.
• Current methods for evaluating HPD effectiveness lack criteria for assessing changes in the speech-to-noise ratio (SNR).
• An ideal HPD should attenuate background noise while preserving speech intelligibility and audibility of warning signals for workers.

Purpose of the Study:

• To investigate the most comfortable listening level (MCL) shift for speech as a potential metric for evaluating speech attenuation by HPDs.
• To compare the MCL shift with established noise attenuation measures, including the Noise Reduction Rating (NRR) and the high-medium-low (H-M-L) method.

Main Methods:

• Measured the HPD-induced shift in the most comfortable listening level (MCL) for speech presented in quiet conditions.
• Compared the measured MCL shift with the Noise Reduction Rating (NRR) and high-medium-low (H-M-L) attenuation values.

Main Results:

• The study indicates that the MCL shift is a sensitive indicator of speech attenuation caused by HPDs.
• The MCL shift, when considered alongside the H-M-L classification, may provide a comprehensive description of HPD technical properties.

Conclusions:

• The most comfortable listening level (MCL) shift shows promise as a metric for assessing the speech audibility aspects of hearing protection.
• Combining MCL shift measurements with H-M-L ratings could enhance the technical characterization of hearing protection devices (HPDs).