vibrotactile identification of signal-processed sounds from environmental events presented by a portable vibrator: a laboratory study

objectives: to evaluate different signal-processing algorithms for tactile identification of environmental sounds in a monitoring aid for the deafblind. two men and three women, sensorineurally deaf or profoundly hearing impaired with experience of vibratory experiments, age 22-36 years. methods: a closed set of 45 representative environmental sounds were processed using two transposing (trha, tr1/3) and three modulating algorithms (am, amfm, ammc) and presented as tactile stimuli using a portable vibrator in three experiments. the algorithms trha, tr1/3, amfm and ammc had two alternatives (with and without adaption to vibratory thresholds). in exp. 1, the sounds were preprocessed and directly fed to the vibrator. in exp. 2 and 3, the sounds were presented in an acoustic test room, without or with background noise (snr=+5 db), and processed in real time. results: in exp. 1, algorithm amfm and amfm(a) consistently had the lowest identification scores, and were thus excluded in exp. 2 and 3. trha, am, ammc, and ammc(a) showed comparable identification scores (30%-42%) and the addition of noise did not deteriorate the performance. discussion: algorithm trha, am, ammc, and ammc(a) showed good performance in all three experiments and were robust in noise they can therefore be used in further testing in real environments.