The reception of environmental sounds through wearable tactual aids

Objective: The objective of this study was to investigate the ability to identify environmental sounds through a wearable tactual aid. Design: A test of the ability to identify environmental sounds was developed, employing closed sets of ten sounds in each of four different settings (General Home, Kitchen, Office, and Outdoors). The participants in the study included a group of three laboratory-trained subjects with normal hearing and a group of three subjects with profound deafness who were experienced users of a tactual device (the Tactaid 7). Identification testing was conducted in each of the four environmental-sound settings using a one-interval, ten-alternative, forced-choice procedure. The laboratory-trained subjects received training with trial-by-trial correct-answer feedback, followed by testing in the absence of feedback using the Tactaid 7 device. The experienced tactual-aid users were tested initially without feedback to establish baseline levels of performance derived from their prior field experience with the Tactaid 7. These subjects then received additional trials in the presence of correct-answer feedback to determine the effects of training on their performance. The data were summarized in terms of overall percent-correct identification scores and information transfer (IT) in bits. Confusion patterns were described using a hierarchical clustering analysis. Results: Post-training results with the laboratory-trained subjects on the Tactaid 7 indicated that performance was similar for the four test environments, with percent-correct scores averaging 65% (and IT of 2.0 bits). For the experienced tactual-aid users, performance was similar across the four environments, averaging 36% correct (and IT of 1.4 bits) for initial testing without feedback. Scores were increased to 60% correct (and IT of 1.9 bits) in the presence of correct-answer feedback. Similar trends were observed in the hierarchical-clustering analysis across both groups of subjects. Within each stimulus set, certain items tended to cluster together, whereas other items tended to appear in single-item clusters. The highly identified stimuli tended to be characterized by unique temporal patterns and confused stimuli seemed to be most similar in terms of their spectral characteristics. Conclusions: Through the multi-channel spectral display of the Tactaid 7 device, subjects were able to identify roughly 2 bits of information in each of four 10-item sets of sounds representative of different environmental settings. Temporal cues appeared to play a larger role in identification of sounds than spectral or intensive cues.