Although 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, UConn 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 Michael Turvey, a professor of psychology, examined people's ability to determine the dimensions of an object, based solely on the sound it made when struck.

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. Although the participants didn't precisely reproduce the object's actual dimensions, they did accurately perceive its shape. For example, square rectangles were perceived as equal in height and width, while long, thin rectangles were perceived as long and thin. The perceived dimensions also were in the vicinity of the actual dimensions.

The researchers say the results were surprising, given that the participants had no foreknowledge of the sizes of the plates and could adjust their reports anywhere within an area of 2.5 x 1.5 meters.

In the second experiment, participants were again asked to determine the height or width of an unseen object after it was struck. The plates were made of steel, Plexiglass or wood. As in the first experiment, the subjects perceived the shapes accurately, regardless of the material.

In the third experiment, participants heard an unseen, steel object being struck and were then asked to identify it as circular, triangular or rectangular. They accurately identified the 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 plates made of three different materials. In only one instance did a participant incorrectly identify the material of the plate. And 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 findings suggest that something in the acoustic pattern allows listeners to perceive one dimension separate from another.

Although much research has been done on aspects of hearing such as pitch and tone, says Turvey, research on how listeners hear events in the world is sparse.

The researchers' work is an important preliminary step in understanding people's ability to hear an object's physical properties.

Allison Thompson