Mechanical and Psychophysical Studies of Surface Wave Propagation during Vibrotactile Stimulation

Tactile displays are often used to present spatial cues about the environment, although the optimal configuration of a display used for spatial cuing is not known. The objective of the present set of experiments was to characterize the properties of surface waves induced by vibrotactile stimulation and to determine if the propagation of surface waves was a factor influencing the ability to localize a point of stimulation in a tactile display. Three sites on the body were tested: the palm of the hand, the forearm, and the thigh. An accelerometer array was fabricated and used to measure the surface waves. The results indicated that there were significant differences between glabrous and hairy skin in terms of the frequency and amplitude of oscillation of the motor. Analyses of the motion of the surface waves across the skin indicated that they were markedly attenuated at 8 mm from the motor, but even at 24 mm the amplitude was still above perceptual threshold. The localization experiment indicated that subjects were much better at identifying the site of stimulation on the palm as compared to the forearm and thigh, and that the latter two sites were not significantly different.