Effect of Subthreshold Vibration on the Perception of Electrovibration

Electrovibration is one of the methods by which users can perceive textures. Electrovibration along with vibrotactile stimulus can enhance texture perception. Several studies have already combined electrovibration and vibrotactile stimuli before, however at threshold or suprathreshold. Multi-modal stimuli at threshold had been reported to exhibit tactile masking inherently. Effect of stimuli at subthreshold and the tactile masking have been missing in the literature. In the current study, a psychophysical experiment was conducted to investigate the effect of subthreshold vibrotactile stimulus (SVS) on the perception of electrovibration. The results from the experiment indicate a reduction of electrovibration threshold by 28.52% at 90% SVS and 16.19% at 80% SVS. The 90% and 80% SVS are vibrotactile input at 90% and 80% of the absolute vibrotactile threshold. The experiment was conducted over a range of frequencies (20-320 Hz) for electrovibration, and the vibrotactile stimulus was maintained 235 Hz. The perception of the combined stimuli was evaluated in a separate experiment using the Likert's scale. The results showed that the sensation of electrovibration is dominating at 80% SVS than 90% SVS. The reduction in threshold of electrovibration (EVT) with SVS indicates the perception of electrovibration increased, and the effect of tactile masking was absent under subthreshold conditions. The study provides significant insights toward developing a texture rendering algorithm based on electrovibration and vibrotactile stimuli.