Benefits of directional microphone for speech perception in reverberant environments

—A study using a university lecture room—

Abstract

The purpose of this study was to examine the potential benefit of a directional microphone for lessening the influence of reverberation in a lecture room on speech understanding. Sentence lists (HINT Japanese) were played back in a sound proof room and in a university lecture room with a reverberation time of 1.6s and were recorded at a distance of 1m from the speaker (“non-reverberant list”) and at 2m and 8m from the speaker (“reverberant list at 2m, 8m”) using both directional and omni-directional microphones. The speech recognition thresholds (SRTs) of the 6 recordings were then determined by 12 listeners with normal hearing. Among the three lists that were recorded using the omni-directional microphone, the SRTs were significantly higher for the recordings made in the room with the higher reverberation. Under the same reverberant conditions, the SRTs of the lists recorded with the directional microphone were significantly lower than those recorded with the omni-directional microphone. Especially, the SRT of the “reverberant list at 2m” was the same as that of the “non-reverberant list”. This study suggests that difficulties in speech understanding arising from reverberation can be improved if people with hearing impairments sit in the front row of the lecture hall and use a directional hearing aid when listening to lectures in reverberant rooms.