Volume 118, Issue 6, December 2005
Index of content:
- SPEECH PERCEPTION 
118(2005); http://dx.doi.org/10.1121/1.2118407View Description Hide Description
This study assessed the acoustic and perceptual effect of noise on vowel and stop-consonant spectra. Multi-talker babble and speech-shaped noise were added to vowel and stop stimuli at to S/N, and the effect of noise was quantified in terms of (a) spectral envelope differences between the noisy and clean spectra in three frequency bands, (b) presence of reliable F1 and F2 information in noise, and (c) changes in burst frequency and slope. Acoustic analysis indicated that F1 was detected more reliably than F2 and the largest spectral envelope differences between the noisy and clean vowel spectra occurred in the mid-frequency band. This finding suggests that in extremely noisy conditions listeners must be relying on relatively accurate F1 frequency information along with partial F2 information to identify vowels. Stop consonant recognition remained high even at despite the disruption of burst cues due to additive noise, suggesting that listeners must be relying on other cues, perhaps formant transitions, to identify stops.
118(2005); http://dx.doi.org/10.1121/1.2126932View Description Hide Description
Although many audio-visual speechexperiments have focused on situations where the presence of an incongruent visual speech signal influences the perceived utterance heard by an observer, there are also documented examples of a related effect in which the presence of an incongruent audio speech signal influences the perceived utterance seen by an observer. This study examined the effects that different distracting audio signals had on performance in a color and number keyword speechreading task. When the distracting sound was noise, time-reversed speech, or continuous speech, it had no effect on speechreading. However, when the distracting audio signal consisted of speech that started at the same time as the visual stimulus, speechreading performance was substantially degraded. This degradation did not depend on the semantic similarity between the target and masker speech, but it was substantially reduced when the onset of the audio speech was shifted relative to that of the visual stimulus. Overall, these results suggest that visual speech perception is impaired by the presence of a simultaneous mismatched audio speech signal, but that other types of audio distracters have little effect on speechreading performance.