Auditory, visual and audiovisual clear speech

Abstract

The speech intelligibility of syllables spoken under conditions of conversational and clear speech was compared. The stimuli were 18 monosyllables (/C-v/) and 18 bisyllables (/v-C-v/) consisting of six voiced-consonants (/b, d, g, v, z, ʒ/) presented in each of three vowel contexts (/a, i, y/). Six female adults were recorded while they produced four iterations of the stimulus set in each of the two speaking styles. The 1728 videotaped test items were edited, randomized and presented to 12 subjects with normal hearing and normal visual acuity under three conditions: visual-only, auditory-only and audiovisually. A broadband noise was mixed with the signal for the latter two conditions. The results revealed a significant three-way interaction of talker, speaking style and perceptual modality. Post-hoc analyses revealed intra and interspeaker differences in speech intelligibility for both speaking styles, in all three perceptual modalities. Overall, positive clear speech effects were observed in all three modalities. Intermodality comparisons revealed differences in the pattern of clear speech effects displayed by individual talkers. This finding indicates that there is not a direct association between the beneficial effects of clear speech in one perceptual modality and its effects on speech intelligibility in another perceptual modality.