Effect of Vibrotactile Stimulation on Auditory Timbre Perception for Normal-Hearing Listeners and Cochlear-Implant Users.

The study tests the hypothesis that vibrotactile stimulation can affect timbre perception. A multidimensional scaling experiment was conducted. Twenty listeners with normal hearing and nine cochlear implant users were asked to judge the dissimilarity of a set of synthetic sounds that varied in attack time and amplitude modulation depth. The listeners were simultaneously presented with vibrotactile stimuli, which varied also in attack time and amplitude modulation depth. The results showed that alterations to the temporal waveform of the tactile stimuli affected the listeners' dissimilarity judgments of the audio. A three-dimensional analysis revealed evidence of crossmodal processing where the audio and tactile equivalents combined accounted for their dissimilarity judgments. For the normal-hearing listeners, 86% of the first dimension was explained by audio impulsiveness and 14% by tactile impulsiveness; 75% of the second dimension was explained by the audio roughness or fast amplitude modulation, while its tactile counterpart explained 25%. Interestingly, the third dimension revealed a combination of 43% of audio impulsiveness and 57% of tactile amplitude modulation. For the CI listeners, the first dimension was mostly accounted for by the tactile roughness and the second by the audio impulsiveness. This experiment shows that the perception of timbre can be affected by tactile input and could lead to the developing of new audio-tactile devices for people with hearing impairment.