Perceptual Evaluation of the Quantization Level of a Vibrotactile Signal.

The quantization of vibrotactile signals is generally performed in the same way as for audio signals. However, the specificities of the sense of touch may allow other choices for the digitization of vibrotactile signals, in particular on the number of quantization bits. The objective of this paper is to define the minimal number of quantization bits, ensuring an imperceptible digitization to touch. For this, a perceptual study is conducted on a set of signals for several quantization levels. For each signal, the total perceptible harmonic distortion (PTHD), taking into account the vibrotactile thresholds, is defined and calculated. PTHD seems to predict a threshold from which the quantization level of the vibrotactile signals is perceptible. This result was obtained by a perceptive study carried out on 29 subjects from pairwise comparison with vibrotactile signals emitted by an electrodynamic transducer placed in a wristband. If the PTHD of a vibrotactile signal is less than 35dB, the digitization effect will be imperceptible. This suggests that 8-bit DACs may be sufficient to generate vibrotactile signals without the digitization effects being perceptible.