Perceptual space of amplitude-modulated vibrotactile stimuli

Amplitude-modulated vibrotactile stimuli have been broadly used for tactile perception and rendering research. However, understandings of the perceptual relations between amplitude-modulated vibrations are not comprehensive yet. In this paper, we present a perceptual analysis on the identifying characteristics of amplitude-modulated vibrations and their perceptual relations. We estimated the perceptual dissimilarities among one carrier and seven amplitude-modulated sinusoidal vibrations (150-Hz carrier frequency; seven modulation frequencies in 1-80 Hz) in a psychophysical experiment. The dissimilarity scores were inspected using multi-dimensional scaling to obtain an appropriate perceptual space. The optimal perceptual space was two-dimensional, where the vibration points exhibited a circular formation. The analysis showed that the pulse-like low-frequency sensation of an amplitude-modulated vibration increased for very low modulation frequencies (1-10 Hz), then decreased for higher modulation frequencies (10-80 Hz), and eventually converged to the smooth vibrational sensation of the 150-Hz carrier signal. It also suggested that the envelope waveform is primary information for the discrimination of amplitude-modulated signals, instead of their spectral energy distributions. These findings can contribute to the design of perceptually salient and distinctive vibrotactile signals using amplitude modulation.