Investigation of Human Tactile Stochastic Resonance Depending on Frequency Effect

Stochastic Resonance (SR) is a significant concern for design of robotic tactile sensors because of its considerable enhancement of sensitivity of human tactile sensation. In the last few decades, researchers have found that noise previously considered detrimental in fact provides the benefit of SR phenomena. However, there are no experimental results for dependence on vibrotactile frequency, which issued as basic data for robotic tactile sensors. In this paper, we investigated the influence of the SR phenomena on human tactile sensation in the context of frequency-dependence of absolute thresholds (AT). We developed a system composed of an experimental apparatus and a computer program based on psychophysics in order to measure the AT of human vibrotactile sensation. We performed three series of psychophysical experiments using normal vibration, 8-mm-sized stimulus point and the continuous sinusoidal signals of 32, 50 and 75 Hz to obtain the AT variation in frequency. The results show that since normal ATs decrease with appropriate noise, SR is observed in normal stimuli tests in the frequency range from 32 to 70 Hz. Since the inclination of the curve of AT in a double logarithmic graph is around -1 in both with-noise and without-noise conditions, SR is caused by the FA-I mechanoreceptive unit in the range of frequency.