Most comfortable loudness shift as a measure of speech attenuation by hearing protectors

The feasibility of using most comfortable loudness (MCL) as a real-world measure of speech attenuation introduced by hearing protection devices (HPDs) was studied. The authors compared three insert HPDs and an earmuff under three test conditions: (a) monaural earphone listening, (b) binaural earphone listening, and (c) sound field listening. The earmuff was used only in the sound-field condition. In addition, three sets of fitting instructions were utilized. Twelve normal hearing subjects participated. Results indicate that MCL shift can be used as a simple measure of speech attenuation provided by HPDs. The observed MCL shifts were affected by the fitting instruction but not by the listening condition. Findings support the notion that MCL-based tests of speech attenuation by HPDs can be conducted reliably both in sound field and under earphones and may be a simple and valid tool for assessing changes in speech audibility due to the wearing of HPDs.