Vibrotactile frequency for encoding a speech parameter

Abstract

Frequency of vibration has not been widely used as a parameter for encoding speech-derived information on the skin. Where it has been used, the frequencies employed have not necessarily been compatible with the capabilities of the tactile channel, and no determination was made of the information transmitted by the frequency variable, as differentiated from other parameters used simultaneously, such as duration, amplitude, and location. However, several investigators have shown that difference limens for vibration frequency may be small enough to make stimulus frequency useful in encoding a speech-derived parameter such as the fundamental frequency of voiced speech. In the studies reported here, measurements have been made of the frequency discrimination ability of the volar forearm, using both sinusoidal and pulse waveforms. Stimulus configurations included the constant-frequency vibrations used by other laboratories as well as frequency-modulated (warbled) stimulus patterns. The frequency of a warbled stimulus was designed to have temporal variations analogous to those found in speech. The results suggest that it may be profitable to display the fundamental frequency of voiced speech on the skin as vibratory frequency, thought it might be desirable to recode fundamental frequency into a frequency range more closely matched to the skin's capability.

Vibrotactile intensity and frequency information in the Pacinian system: A psychophysical model

“…This process was repeated using different standard frequencies. The Weber fraction predicted by the model was found to be constant at 0.22 and matched almost exactly that measured by Mountcastle et al (1969) and Rothenberg et al (1977) for sinusoidal stimuli.…”

“…One of the central assumptions underlying the model is that Δf /f is constant across frequencies (Franzén & Nordmark, 1975;Horch, 1991;Mountcastle et al, 1969;Rothenberg et al, 1977). The only other plausible assumption would be that Weber fractions increase with frequency, as has been found to be the case by Goff (1967).…”

“…There is disagreement as to the form of the psychometric function relating frequency difference limens (DL) to frequency of the standard. In developing the model, we assumed that the Weber fraction was constant across frequencies (see Franzén & Nordmark, 1975;Horch, 1991;Mountcastle et al, 1990;Mountcastle et al, 1969;Rothenberg, Verrillo, Zahorian, Brachman, & Bolanowski, 1977). The possibility that Δf /f increases with frequency, as has been found to be the case by Goff (1967), is explored below.…”

Primacy of dimensions in vibrotactile perception: An evaluation of early holistic models

“…The pattern was similar in vibrotaction whether the frequency range was high (pacinian) or low (Pacinian and non-Pacinian). It is also interesting to note that the psychological differences along dimensions were relatively small in this study (see Craig, 1972;Rothenberg et al, 1977), and appreciably smaller than in Melara and Marks's auditory study. Apparently, the magnitude of stimulus differences is inconsequential to the overall pattern of effects of orientation on RT (cf.…”

Contours of equal perceived amplitude and equal perceived frequency for electrocutaneous stimuli

“…Pulses applied through a large contactor (1.9 em diameter) on glabrous skin apparently activate pacinian corpuscles, and perceived amplitude increases with both the frequency and the number ofpulses as though passing through an energy integrator with a 200-msec time constant (Verrillo, 1965; although see Sherrick, 1985). In marked contrast, pulses delivered through a small contactor (diameter < 0.16 em; Verrillo, 1965) or to hairy skin (Rothenberg, Verrillo, Zahorian, Brachman, & Bolanowski, 1977) show little or no integration at or above threshold, suggesting that they excite one or more of the non-pacinian receptor systems known to lack temporal integration (for reviews of receptor systems in glabrous and hairy skin, see Bolanowski, Gescheider, & Verrillo, 1994;Bolanowski, Gescheider, Verrillo, & Checkosky, 1988). Perhaps electrical stimuli also excite these non-pacinian receptors, resulting in relatively flat electrocutaneous contours of equal perceived amplitude, although the mechanism for such selectivity is uncertain (e.g., Blamey et aI., 1990).…”