Optimum Reverberation for Speech Intelligibility for Normal and Hearing-Impaired Listeners in Realistic Classrooms Using Auralization

The objective of this study was to use auralization techniques to investigate the optimal reverberation for speech intelligibility for normal-hearing and hearing-impaired adult listeners in classrooms with non-diffuse sound fields. This extended a previous study involving rooms with diffuse sound fields to more realistic rooms. Modified Rhyme Test (MRT) signals were auralized in six virtual classroom configurations with different reverberation times. Each classroom contained a speech source, a listener at a receiver position, and a noise source located between the talker and the listener. Two speech- and noise-source output-level differences (0 and +4 dB) were tested. Subjects performed speech-intelligibility tests in the virtual classrooms to identify the reverberation time that gave the best results in each case. For both normal and hearing-impaired listeners, the optimal reverberation time was generally non-zero, and increased with decreased speech-to-noise level difference. Hearing-impaired subjects apparently required more early energy than normal-hearing subjects. The optimal reverberation time for speech intelligibility in classrooms is not necessarily zero, as is commonly believed. The optimal value is generally non-zero, and varies with the room, the locations of the speech and noise sources and the listener, and the noise level.