Amplitude envelopes and speechreading Free

Amplitude envelopes derived from filtered bands of speech provide varying degrees of benefit to speechreading. Three parameters related to envelope extraction are examined using both easy and difficult sentence materials: (1) the bandwidth and center frequency of the filtered speech signal used to obtain the envelope, (2) the bandwidth of the envelope signal, and (3) the carrier signal used to convey the envelope. Thus far, results for normal hearing subjects presented with difficult speech materials suggest that: (1) the envelope of wideband speech did not always provide the greatest benefit to speechreading when compared to envelopes derived from octave bands of speech; (2) as the bandwidth of the envelope signal increased from 100–4000 Hz, auditory‐visual (AV) performance improved slightly, whereas bandwidths below 100 Hz resulted in AV scores that were equal to or worse than speechreading alone; and (3) low‐frequency carrier signals were better than high‐frequency or wideband carrier signals, at least for envelopes derived from an octave band of speech centered at 500 Hz. Similar tests with easy speech materials are in progress. [Work supported by NIH.]