A wearable tactile intonation display for the deaf

A wearable device is described which represents the fundamental frequency of voiced sounds as the locus of pitch-synchronous vibrotactile stimulation of the skin. The pitch extractor, which accepts inputs from either a microphone or an accelerometer, uses a combination of low-pass filtering and peak detection to generate a square wave whose frequency is half that of the fundamental frequency of the speech signal. Using a shift register and a clock, the first half of each cycle is timed, the result determining which of eight output channels is actuated during the second half. The output transducer array consists of eight miniature solenoids mounted in a small plastic box. The electronics package is worn on a belt and the solenoid array is mounted on the forearm. The system is powered by thee 9 V NiCad batteries and runs for 2 to 3 h between charges. Experiments with normally hearing subjects confirmed that single channel changes of stimulus location can be detected with relative ease. It was also demonstrated that the system permits discrimination among some of the principal intonation contours of English. The potential value of this device in the rehabilitation of hearing-impaired children is currently under investigation.