Bats use echos to find food and avoid objects. Credit: © GettyImages

A bat-inspired sonar walking stick could help visually impaired people sense their surroundings.

The lightweight device emits sound too high-pitched for the human ear to detect. It also picks up the reflections of these waves to map obstacles up to three metres away in three dimensions. Buttons on the cane's handle vibrate gently to warn a user to dodge low ceilings and sidestep objects blocking their path.

So far the cane has been tested by 25 visually impaired people in Britain, Germany, Canada and Australia. Participants received 30 minutes of training. "Feedback was very positive," designer Dean Waters told this week's British Association Festival of Science in Salford. "Plus, people on the street were really interested in these modern gadgets."

Waters, a zoologist at the University of Leeds, UK, got his inspiration by watching bats find food. "They echolocate, like submarines," he says. The animals emit ultrasonic chirps that bounce back off their mosquito prey. Bats work out the distance to dinner by timing the echo's return - a long delay means the snack is far away.

Waters' team devised a system small enough to mount on a white walking stick that sends 60,000 sound pulses per second and receives the faint echoes. Four pulsating pads on the stick's handle enable a blind walker to feel the strength of the ultrasound reflections. A fast and strong signals means that an obstacle is close.

Due to be manufactured commercially by the end of the year, the canes should cost around £400 (US$635) each.

Joanne Baker is a British Association Media Fellow