Vibrotactile sensitivity in active finger pressing

Abstract

An experiment was performed to study the effect of actively applied forces on vibrotactile thresholds. The task consisted in pressing the fingertip against a flat rigid surface which provided broadband vibration noise of varying amplitude. Three force levels were considered, ranging from light touch to hard press. Possibly due to the concurrent effect of large contact area, spectrally complex stimuli and active pressing force, the measured sensitivity thresholds are considerably lower than what is found in most of the previous literature. Moreover, significant differences in thresholds were found between the lowest and middle force level, and the highest and middle force level.

Vibrotactile Sensitivity in Active Touch: Effect of Pressing Force

“…Thresholds were highest at the Low force condition, and decreased significantly at both Mid and High force levels. In good accordance with what reported in our preliminary study [21], for noise vibration the lowest threshold was obtained at the Mid force condition, while at the Low and High conditions thresholds were higher, resulting in a U-shaped threshold contour with respect to the applied force. However, considering that the spectral centroid of the noise vibration generally shifted towards 300 Hz and higher frequencies for the Mid and High force conditions (Section 2.4 and the appendix, available in the online supplemental material), we suggest that the U-shape of the threshold-force curve might be partially due to the response of the Pacinian channel, which has a U-shaped contour over the frequency range 40-800 Hz with maximum sensitivity in the 200-300 Hz range [2].…”

“…A previous experiment considering only the noise condition had been performed a year earlier without contact area measurement [21]. One participant in each condition of the experiment presented here had also performed the previous experiment.…”

“…Two participants-one in each vibration condition-had taken part in a related experiment a year earlier [21]. In order to verify the possible effect of learning on them, t-tests were computed to compare their individual mean thresholds in the current experiment with those of the remaining naive participants.…”

“…Indeed, novel technology and approaches have been developed in recent years, which open new possibilities in this regard [18], [19], [20]. Extending a previous study by some of the present authors [21], we designed an experiment to investigate vibrotactile sensitivity while addressing the following factors: active pressing force, unconstrained contact of the finger pad, broadband or sinusoidal vibration stimuli. In this rather ecological setting, sensitivity thresholds were examined as participants actively exerted different contact forces.…”

Perception of Vibrotactile Cues in Musical Performance

“…Thresholds were highest at the Low force condition and decreased significantly at both Mid and High force levels. In good accordance with what reported in a preliminary study [44], for noise vibration the lowest threshold was obtained at the Mid force condition, while at the Low and High conditions thresholds were higher, resulting in a U-shaped threshold contour with respect to the applied force. However, as shown in Sect.…”