The Effect of Skin Temperature on Vibrotactile Sensibility and Its Model
Hideto Ide and Masafumi Uchida
College of Science & Engineering, Aoyama Gakuin University, 6-16-1 Chitosedai, Setagaya-ku, Tokyo, 157 Japan
The vibration problems of living bodies have so far been studied from the perspectives of engineering, physiology, and psychology. This study shows the relationship between vibratory sensibility and temperature in the living body. Psychological experiments were carried out by using the vibrometer of an acoustical calibration apparatus in sine, triangular, and square waves. The sensibilitythreshold measurements were made using 30-700 Hz sine waves, 30-300 Hz triangular and sawtooth waves, or 30250 Hz square waves. Each of ten subjects was kept seated. The average value of the vibratory levels, varied by ascending and descending steps, was taken as that of the threshold. As the vibrometer in the apparatus used makes a noise at frequencies greater than 250 Hz, it was masked from the subjects by presenting them with a different noise. The threshold curve for square waves was lower by 12.3 dB than that for sine waves at about 30 Hz. The threshold curve of the 26°C sine wave was lower by 10 dB than that of the 58°C sine wave vibration near 200 Hz. At stimulated frequencies above 120 Hz, the lowering of the temperature of the contact point caused the amplitude threshold to increase and the frequency at which the threshold curve was at a minimum to shift to a lower frequency. In addition, a model of the vibratory sensibility system was constructed by electronic circuits. Its spatio-temporal characteristics were compared with the neurophysiological and psychological data on human vibratory sensibility. The results showed the qualitative agreement with the fundamental neurophysiological and psychological data.