Auditory-visual tone perception in hearing impaired Thai listeners

This study investigated the effects of hearing impairment and auditory vs. auditory-visual perception of lexical tone by native Thai hearing impaired listeners: Hearing Impaired with Hearing Aids (HI+HA), Hearing Impaired without Hearing Aids (HIHA), and Normal Hearing (NH). Adults’ discrimination of the 5 Thai tones was investigated in auditory-visual (AV), auditoryonly (AO), and visual-only (VO) conditions. Generally, NH participants performed better than the two HI groups with hearing aids facilitating tone perception (HI+HA > HI-HA). The Falling-Rising (FR) pair of tones was the easiest to discriminate for all three groups and there was a similar ranking of the relative discriminability of all 10 tone contrasts across groups. There was better tone discrimination in AV than in AO and both were much better than VO; and this was equally the case for all groups. The results show that Hearing Impaired individuals either with or without hearing aids can and do use visual speech information to augment auditory perception of tone, but do so in a similar, not a significantly more enhanced manner as the Normal Hearing individuals.