Trans. Tech. Comm. Psychol. Physiol. Acoust., The Acoustical Society of Japan, Vol. 35, No. 4, H-2005-41, pp. 237-242, 2005 (in Japanese)
Degradation of speech intelligibility in time-reversed reverberation
Abstract: We investigated whether speech in time-reversed reverberation is less intelligible than that in normal (non-time-reversed) reverberation. We generally perform speech communication without noticing the existence of reverberation. Moreover, it is known that reverberation is evident when we play a speech signal recorded in a reverberant room backward in time. However, few quantitative studies have shown speech intelligibility in time-reversed reverberation. We, therefore, conducted a perceptual experiment to compare speech intelligibility between signals convolved with normal and time-reversed impulse responses of a room. The reverberation times (RTs) used were 1.0, 1.5, and 2.0 s. Twenty-four subjects participated in the perceptual experiment; each subject was instructed to listen to 24 sentences under different experimental conditions. As a result, speech intelligibility significantly decreased at all RTs: from 98.6% to 92.2% (RT=1.0 s), from 95.4% to 82.2% (RT=1.5 s), and from 93.9% to 63.7% (RT=2.0 s). This might reflect the temporal asymmetry of both the human auditory system and a speech sound itself.
Keywords: time-reversed reverberation, speech intelligibility, perceptual overlap masking, onset and coda of syllable, Haas effect