Sound information notification system by two-channel electrotactile stimulation for hearing impaired persons

Hearing impaired persons (HIPs) are afraid of walking along a street and living a life alone. If they can successfully get sound information via some machine interface, dangerous situations outdoors will be avoided, and their quality of life indoors will be improved. This paper describes a notification system for transmitting sound information to HIPs with two-channel electrotactile stimulation, assuming that it is used both outdoors and indoors. The proposed system consists of two subsystems: one is a block which detects sound information and another one is to transmit the detected sound information with electrotactile stimulation. In the system developed, sound information is provided with the attention arousal, notifying the direction of the sound source (four states) and the sound category (seven states). Thus, 28 states of sound information are sent. We adopted 12 stimulation patterns comprising several burst profiles, each burst composed of several pulses modulated in amplitude. In the first subsystem, recognition ratio of the direction was 90% and detection ratio of the sound category was 80%. In the second subsystem, recognition experiments for the direction of the sound source and the sound category performed for four healthy subjects showed that the average percentages of correct recognition were 91 % and 89 %, and the reaction times 1.21 seconds and 1.62 seconds. These results suggested the possible applicability of the proposed system to assist HIPs.