A Comparison of Auditory and Tactual Presentation of a Single-Band Envelope Cue as a Supplement to Speechreading

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Research on auditory supplements to speechreading has clearly demonstrated that even highly simplified auditory signals can lead to substantial improvements in intelligibility. In general, the effects observed with such auditory supplements are greater than those typically observed with tactual aids to speechreading. The purpose of the current study was to compare benefits to speechreading of a supplementary low bandwidth signal presented through either the auditory or tactual system. The supplementary signal, which consisted of a 200 Hz carrier amplitude modulated by the envelope of an octave band of speech centered at 500 Hz, was presented through a high- performance single-channel vibrator for tactual stimulation or through headphones for auditory stimulation. Performance of normal-hearing subjects on the reception of words in sentences and the reception of several suprasegmental properties was examined under conditions of speechreading alone and speechreading supplemented by either the auditory or tactual signal. Benefits to speechreading were observed with both the auditory and tactual supplements for the reception of words in sentences. The size of the benefit observed with the tactual signal was roughly one-third of that observed with the auditory signal. In suprasegmental tests of the ability to discriminate rising from falling pitch contours and the location of the stressed word in a short phrase, neither the auditory nor tactual supplement resulted in improvements in performance over speechreading alone. Possible explanations for the differential effects obtained for auditory and tactual presentation of the same envelope cue are discussed.

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