How humans develop echolocation skills is revealed in new research

Like our fellow mammals, dolphins and bats, humans can find their way through an environment by making sounds and listening for the echoes. With practice, we can learn to use the volume, pitch and timbre of echoes from a tapping cane, or one’s own voice, to navigate an environment without relying on sight, says Bo Schenkman , an associate professor at KTH Royal Institute of Technology in Stockholm.

Unlike with dolphins and bats, echolocation is a byproduct of human hearing, not a sense in itself. However, people who are blind from an early age are better at echolocation, says Schenkman, who is doing research that explores how people can be trained to use this ability even later in life.

While the ability to detect volume and pitch shifts is known, Schenkman reports  that preliminary research shows people are able to also detect the timbre of an echo, that is, the characteristics that give a sound its distinctness. Timbre, for example, is the quality that enables us to tell a violin from a cymbal, even if they are in the same volume and pitch.

Schenkman’s research shows that visually impaired people are on average better at perceiving the quality of two sounds that are close together in time. He also finds that blind people can more easily counteract the "precedence effect," a phenomenon that occurs when sounds overlap, and a person judges the location of the sounds to be from the location of the first arriving sound, rather than from the ones that arrive later.

Previously a lecturer in the subjects of human-computer interaction and psychology, Schenkman works in the Department of . He presented his findings recently at the Acoustical Society of America and the European Acoustics Association, in Boston, Massachusetts.

David Callahan