bratakos2001 implements the single-band envelope cue described in
Maroula S. Bratakos, Charlotte M. Reed, Lorraine A. Delhorne, Gail Denesvich, "A single-band envelope cue as a supplement to speechreading of segmentals: A comparison of auditory versus tactual presentation." Ear and Hearing 22, no. 3 (2001): 225-235.
The method takes input audio and produces one channel of tactile output, based on filtering and extracting an amplitude envelopes.