Comparison of speech intelligibility scores for direct listening and headphone playback

Abstract

Speech recognition test scores from direct listening and headphone playback were compared to validate the use of headphone playback for investigating the effects of varied room acoustics conditions. Varied acoustical conditions for direct listening, that were representative of classrooms, were achieved using simulated sound fields in an anechoic room with an 8-channel electro-acoustic simulation system. Eight conditions consisting of the combinations of 2 reverberation times and 4 signal-to-noise ratios were used. By recording these conditions with an acoustical mannequin, headphone playback of the same conditions could be achieved and the corresponding speech recognition scores compared. Two different approaches for correcting for the microphone and headphone responses were compared. Subjects also responded to a short questionnaire to describe the audible differences between direct playback and headphone listening. Because spatial characteristics were frequently found to differ between the two listening modes, further comparisons were carried out using sound fields with systematic differences in the locations of the speech and noise sources. Although there were always some audible differences between the two playback modes, it was possible to obtain the same speech recognition scores using headphone playback as with direct listening. [Work supported by CLLRnet.]