Vibrotactile perception: examining the coding of vibrations and the just noticeable difference under various conditions

High-frequency vibrations are an essential part of numerous manipulation tasks. A promising research area, in particular, are telemanipulation tasks where vibrations occurring in the remote environment are fed back through tactile displays. Three experiments concerning the perception of vibrations were conducted. The first experiment aims at determining whether vibrations are coded primarily by frequency, amplitude, or acceleration by human participants. Results show that primarily frequency and amplitude, but not acceleration of the vibrations were perceived. In the second experiment, participants’ just noticeable difference (JND) for frequency under different conditions was examined. The resulting JND of 18% for frequencies showed dependence neither on the amplitude or acceleration, which were independently held constant, nor on the reference frequencies. Therefore, it is not necessary to adjust the subjective intensity for vibrations for each human operator when designing and using tactile displays. In the third experiment, the stimuli and the procedure of the second experiment were replicated using different configurations and a mere force-output device. The resulting JNDs were 21% for vibrations of 100 Hz, and 17% for vibrations of 150 Hz and above. Furthermore, there was no visual dominance over the haptic modality regarding the JND for frequencies.