Research Proposal: Vibrotactile Body Mapping of Sound Wave Vibrations Near the Skin

By Grant Powell
School of Behavioral and Brain Sciences, University of Texas at Dallas
ACN 6332 Perception
Professor Rachna Raman
May 4, 2023

Purpose

The focus of this research proposal is to answer the following research question: Where on the body is there the most sensitivity to soundwave vibrations as it hits the skin not when they are introduced through a medium attached to the skin, but when it is unattached and away near the skin’s surface? This idea is similarly based on a perceptual measurement concept from the 1800s called the Just Noticeable Difference (JND) according to Weber’s Law by German psycho-physicist Ernst Weber. It is centered around the question of what is the smallest detectable change in the intensity of a stimulus needed for a person to notice that either the stimulus is being perceived or there are two or more stimuli being perceived instead of one? Basically, a mean average relative threshold of noticing whether a stimulus or stimuli are being felt, heard, smelt, tasted, or viewed is being searched for. Although there have been experiments in the past that have utilized this concept to answer research questions like the one being proposed here, they were all done in a slightly different manner.

Background

In a comprehensive bibliography by Proctor (1984), the first experiment on testing sensitivity to soundwave vibrations through touch to determine if they can be heard this way was in 1924 by Robert H. Gault. Gault transmitted his own speech soundwave vibrations by speaking through a tube’s 14-foot-long air column that contacted the surface of the palm of a normal-hearing subject’s hand. The subject whose hearing was completely muted in the lab was able to correctly match the vibrations with 34 English words in non-sentence form and comprehend the meaning of those words in sentence form in various combinations (Gault, R.H., 1924 & 1926). Through a Gault-teletactor in an experiment by Goodfellow (1934), it was found, though not statistically significant, that at the lowest possible decibel the highest sensitivity amongst 13 body areas of 2 totally deaf and 4 normal hearing subjects to speech and music soundwave vibrations at 64 Hz was in the left index finger, at 256 Hz was in the palm of the right hand, and at 1,024 Hz was in the fingernail of the right index finger. Although these experiments and later experiments that expanded on these findings only used measurement apparatuses that contacted the skin and put a higher focus on touch sensitivity to speech soundwave vibrations instead of music soundwave vibrations (Proctor, A, 1984), the goal of the proposed research is still going to be like the experiment by Goodfellow.

Hypothesis

Therefore, the following research hypothesis will be posited: When introduced to music soundwave vibrations through a medium unattached and away near the skin’s surface, any part of the hand will be considered the body area most sensitive to soundwave vibrations in comparison to the other body areas.

Method

The proposed research will use an apparatus of some kind involving a sound speaker fitted with a cone over it to help filter the sound through the hole of the cone onto a specific body area without touching the skin much in the same way that the pinna of the human ear helps filter soundwaves directly into the ear. The same frequencies of soundwaves in Goodfellow (1934) will be introduced through the apparatus onto the skin region of a certain body area. First, it will make direct contact onto the skin to develop a baseline decibel range that can be felt. Second, the apparatus will be moved back .5 inches away from the skin’s surface and the decibel knob turned down until the frequency of the soundwave vibrations cannot be felt. Third, continue repeating step two until the frequency, itself, cannot be felt and measure the distance from the body area.

Reference

Gault, R.H. (1924). Progress in experiments on tactual interpretation of oral speech. The Journal of Abnormal Psychology and Social Psychology, 19(2), 155-159. https://doi.org/10.1037/h00657 52 (/doi/10.1037/h0065752)

Gault, R.H. (1926). Tactual interpretation of speech. The Scientific Monthly, 22(2), 126-131. https://www.jstor.org/stable/7438

Goodfellow, L.D. (1934). The sensitivity of various areas of the body to vibratory stimuli. The Journal of General Psychology, 11(2), 435-440, https://doi.org/10.1080/00221309.1934.9917848

Proctor, A. (1984). Tactile aids for the deaf: A comprehensive bibliography. American Annals of the Deaf, 129(5), 409-416. https://www.jstor.org/stable/44399523