People hear shape, UConn researchers find (Released: 2/25/00)
by Allison Thompson, Office of University Communications
STORRS, Conn. -- While identifying the source of a sound is important, ascertaining the source's physical properties can play an equally critical role in determining a person's response to the sound. In recently completed research, University of Connecticut scientists found that people are able to hear the shape of a vibrating object.
In "Hearing Shape," published in the February issue of Journal of Experimental Psychology: Human Perception and Performance, Andrew Kunkler-Peck of UConn's Center for the Ecological Study of Perception and Action and Psychology Professor Michael Turvey examined people's ability to determine the dimensions of an object based solely on the sound it made when struck.
While much research has been done on aspects of hearing such as pitch and tone, research on how listeners hear events in the world is sparse, Turvey says. Kunkler-Peck and Turvey's current work is an important preliminary step in understanding people's ability to hear an object's physical properties.
In the first of four experiments, participants were asked to record either the height or width of an unseen, steel plate after it was struck. While the participants didn't precisely reproduce the object's actual dimensions, they did accurately perceive its shape. For example, square objects were perceived as equal in height and width while long, thin rectangles were perceived as long and thin. In addition, the perceived dimensions were in the vicinity of the actual dimensions and were ordered properly, Kunkler-Peck and Turvey write.
"This pattern of results suggests that participants' responses were scaled by definite impression of the height and width of the plates," they write.
In the second experiment, participants were again asked to determine the height or width of an unseen object after it was struck. In this experiment, the plates were made of steel, Plexiglass and wood. As in the first experiment, the subjects perceived the shapes of the plates accurately regardless of the material.
In the third experiment, subjects heard an unseen, steel object being struck and were then asked to identify it as circular, triangular or rectangular. According to the experiment's results, the participants accurately identified the correct shape at a level well above chance.
In the final experiment, participants were asked to discern, again on the basis of hearing alone, the shape and material composition of three different plates made of three different materials. In only one instance did a participant incorrectly identify the material of the plate, misidentifying Plexiglass as steel. For each shape category, participants accurately identified the shape at a level well above chance.
"In sum, the shapes of thin, vibrating plates can be heard," Kunkler-Peck and Turvey write.
The current findings suggest that something in the acoustic pattern allows listeners to perceive one dimension or another. Given the intent to perceive height, it seems that a listener can detect the modal frequencies associated with it separately from those associated with width. The same can be said for the intent to perceive width.
Kunkler-Peck and Turvey write, "The ability of listeners to attend to one aspect of a vibrating body over other aspects suggests that there must be a level of differentiation in the acoustic pattern to support the individual perceptions."