The role of tactile aids in providing information about acoustic stimuli

Devices that convert sound patterns into patterns of vibrotactile stimulation have been shown in laboratory and clinical studies to enable persons to appreciate many aspects of the acoustic environment, and thus are of potential benefit to deaf persons. In the present article, a framework is outlined for describing normal listening situations as a hierarchy of tasks requiring increasingly complex analysis of the acoustic waveform, including sound detection, environmental sound identification, syllable rhythm and stress categorization, phoneme and word identification, and comprehension of connected speech. The types of benefits provided by tactile aids in each of these tasks are exemplified using data from studies of single-channel commercially available devices and multichannel tactile vocoders in our own and other laboratories. The discussion of these data addresses such issues as the features of the acoustic environment that can or should be transmitted through a tactile aid, the differences in the information transmitted by commercially available versus experimental laboratory devices, the comparison of tactile aids and cochlear implants, and the technical problems that remain to be overcome in the design and evaluation of improved vibrotactile aids.