Summary: | The purpose of this study was to measure effects of speechreading and signal-to-noise
ratio (SNR) on understanding mainstream American English (MAE) heard by 30 Indian adults
compared to 30 American adults. Participants listened to a recording of a female speaker of MAE
saying 10 lists of 10 different Everyday Speech Sentences per list. Participants heard sentences
from a TV loudspeaker at a conversational speech level while a four-talker babble played
through two surrounding loudspeakers at a +6, 0, -6, -12, or -18 dB SNR. Participants heard and
watched a different list of sentences at each SNR (i.e., through the Auditory-Visual modality) and
only heard a different list of sentences at each SNR (i.e., through an Auditory modality). After
listening to each sentence, participants wrote verbatim what they thought the speaker said. Each
participant’s speechreading performance at each SNR was computed as the difference in words
correctly heard through Auditory-Visual versus Auditory modalities. Consistent with most
previous research, American participants benefitted significantly more from speechreading at
poorer SNRs than at favorable SNRs. The novel finding of this study, however, was that Indian
participants benefitted less from speechreading than American participants at poorer SNRs, but
benefitted more from speechreading than American participants at favorable SNRs. Linguistic
(and, possibly, nonlinguistic) variables may have accounted for these findings; including an
increased need for Indian participants to integrate more auditory cues with visual cues to benefit
from speechreading, presumably because they only spoke English as a second language. These
findings have theoretical implications for understanding the role of auditory-visual integration on
cross-language perception of speech, and practical implications for understanding how much
speechreading helps people understand a second language in noisy environments. === Thesis (Ph.D.)--Wichita State University, College of Health Professions, Dept. of Communication Sciences and Disorders
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