Palm-area sensitivity to vibrotactile stimuli above 1~{kHz}

The upper limit of frequency sensitivity for vibrotactile stimulation of the fingers and hand is commonly accepted as 1 kHz. However, during the course of our research to develop a full-hand vibrotactile musical communication device for the hearing-impaired, we repeatedly found evidence suggesting sensitivity to higher frequencies. Most of the studies on which vibrotactile sensitivity are based have been conducted using sine tones delivered by point-contact actuators. The current study was designed to investigate vibrotactile sensitivity using complex signals and full, open-hand contact with a flat vibrating surface representing more natural environmental conditions. Sensitivity to frequencies considerably higher than previously reported was demonstrated for all the signal types tested. Furthermore, complex signals seem to be more easily detected than sine tones, especially at low frequencies. Our findings are applicable to a general understanding of sensory physiology, and to the development of new vibrotactile display devices for music and other applications.