Science Is Unlocking The Secrets Of 'Seeing' Through Sound

Scientists are studying the notion of human echolocation with hopes that it may one day be possible to teach the visually impaired and others how to navigate the world through sound like a bat winging its way through a pitch black cave, but without the wings.

Many people who were born blind or lost sight later in life learn to use a variety of sounds to make their way safely through environments by listening to the pitch, loudness and timbre of the resulting echoes. Tapping a cane is a popular way to hear how the sound it makes bounces off walls and other objects, although clicks, shushing sounds and snapping noises are also used.

Bo Schenkman, an associate professor at Stockholm's KTH Royal Institute of Technology, presented a summary of his work on human echolocation at a joint meeting of the Acoustical Society of America and the European Acoustics Association Sunday in Boston.

Schenkman has found that people without sight can be particularly adept at detecting not just the pitch and volume of echoes, but also the timbre, particularly the sharpness aspects of timbre. In this way, it appears that people may actually be able to acquire the ability to better discern higher frequencies. He also finds that people who are visually impaired are better than sighted individuals at "separating" overlapping sounds to judge their origin.

Schenkman says that while the type of echolocation used by bats and humans is similar -- for example, there is an ideal interval for each for emitting sounds in order to echolocate -- humans listen for both a sound and its echo. Bats, on the other hand, rely more on just the echo for navigation help.

"It's a byproduct of our hearing system that we can use echolocation, so we're not as proficient at it as bats," Schenkman said.

But he adds that he thinks there is still much to learn in comparing the way people and bats use echoes differently. His goal is to use his work to improve ways to train people without vision, particularly those that lose it later in life, to navigate the world better through sound.