Auditory-Visual Lexical Tone Perception in Thai Elderly Listeners with and without Hearing Impairment

Lexical tone perception was investigated in elderly Thais with Normal Hearing (NH), or Hearing Impairment (HI), the latter with and without Hearing Aids. Auditory-visual (AV), auditory-only (AO), and visual-only (VO) discrimination of Thai tones was investigated. Both groups performed poorly in VO. In AV and AO, the NH performed better than the HI group, and Hearing Aids facilitated tone discrimination. There was slightly more visual augmentation (AV>AO) for the HI group, but not the NH group. The Falling-Rising (FR) pair of tones was easiest to discriminate for both groups and there was a similar ranking of relative discriminability of all 10 tone contrasts for the HI group with and without hearing aids, but this differed from the ranking in the NH group. These results show that the Hearing Impaired elderly with and without hearing aids can, and do, use visual speech information to augment tone perception, but do so in a similar, not a significantly more enhanced manner than the Normal Hearing elderly. Thus hearing loss in the Thai elderly does not result in greater use of visual information for discrimination of lexical tone; rather, all Thai elderly use visual information to augment their auditory perception of tone.