Speechreading supplemented with frequency-selective sound-pressure information.

The benefit of supplementing speechreading with frequency-selective sound-pressure information was studied by auditorily presenting this information to normal-hearing listeners. The sound-pressure levels in one or two frequency bands of the speech signal with center frequencies of 500, 1600, and 3160 Hz, respectively, and with 1- or 1/3-oct bandwidth were used to amplitude-modulate pure-tone carriers with frequencies equal to the center frequencies of the filter bands. Short sentences were presented to 18 normal-hearing listeners under the conditions of speechreading-only and speechreading combined with the sound-pressure information. The mean number of correctly perceived syllables increased from 22.8% for speechreading-only to 65.7% when sound-pressure information was supplied in a single 1-oct band at 500 Hz and to 86.7% with two 1-oct bands at 500 and 3160 Hz, respectively. The latter signal scored only 26.7% correct syllables without accompanying visual information.