Effects of reverberation on speech segregation
John F. Culling, Chaz Yee Toh, Kathryn I. Hodder · The Journal of the Acoustical Society of America · 2002
Perceptual separation of speech from interfering noise using binaural cues and fundamental frequency (F0) differences is disrupted by reverberation [Plomp, Acoustica 34, 200–211; Culling et al., Speech Commun. 14, 71–96]. Culling et al. found that the effect of F0 differences on vowel identification was robust in reverberation unless combined with even subtle F0 modulation. In the current study, speech reception thresholds (SRTs) were measured against a single competing voice. Both voices were either monotonized or normally intonated. Each came from recordings of the same voice, but interfering sentences were feminized (F0 increased 80%; vocal-tract length reduced 20%). The voices were presented from either the same or from different locations within anechoic and reverberant virtual rooms of Culling et al. In anechoic conditions, SRTs were lower when the voices were spatially separated and/or intonated, indicating that intonated speech is more intelligible than monotonous speech. In reverberant conditions (T60=400 ms), SRTs were higher, with no differences between the conditions. A follow-up experiment introduced sentences with inverted F0 contours. While acceptable in quiet, these sentences gave higher SRTs in all conditions. It appears that reverberant conditions leave intonated speech intelligible, but make it unseparable, while monotonous speech remains separable but is unintelligible.