Dependence of the Perceptual Discrimination of High-Frequency Vibrations on the Envelope and Intensity of Waveforms

Humans perceive and discriminate high-frequency tactile vibrations based on the intensity and envelope of the stimuli. However, no studies have investigated exactly how the envelope and intensity each affect the ability to discriminate. The objectives of this paper are to identify the boundary at which the envelope begins not to strongly affect the ability to discriminate vibrations and to investigate the effects of the carrier frequency and intensity on the discrimination ability. The results of our testing showed that the ability to discriminate was dependent on the envelope frequency and that the ability to discriminate sinusoidal and amplitude-modulated (AM) vibrations in which the envelope frequency ranged from 12 to 50 Hz was higher than that required to discriminate sinusoidal and AM vibrations in which the envelope frequency was above 80 Hz. When the envelope frequency of an AM vibration was 125 Hz, the ability to discriminate sinusoidal and AM vibrations was found to be low and no significant difference was noted in comparison to discriminating AM vibrations with the same envelope frequency. These results suggest that the boundary for envelope perception was at an envelope frequency of around 80-125 Hz at low intensities and that the carrier frequency had little effect on the discrimination, although the discrimination ability tended to increase as the intensity increased.