Subjective Magnitude Functions for Vibrotaction

An investigation of the subjective magnitude of vibrotaction was undertaken in order to 1) determine the growth of sensation as a function of intensity at a number of different frequencies; 2) establish contours of equal subjective intensity for vibrotaction; and 3) compare the psychophysical methods of direct scaling and intensity matching for a wide range of intensity and frequency. The results show that the growth of sensation is a power function having a slope of about 0.89 for frequencies up to 350 Hz. Near the threshold of detectability the subjective magnitude is proportional to the physical intensity. Contours of equal subjective magnitude were established at eleven levels of intensity and across ten frequencies. It is clearly shown that data obtained by direct scaling and by interfrequency-intensity matching are comparable.