Blind taught to ‘see’ like a bat

Blind British children are to be taught a pioneering bat-style echolocation technique to visualise their surroundings. The children are learning how to build up detailed images of the world around them by clicking their tongue and interpreting the sound as it echoes back.

The technique is used by animals such as bats, dolphins and whales to navigate and hunt in the dark. Bats are able to manoeuvre around caves and catch tiny insects on the wing by emitting short bursts of high-pitched noise and reading the sound waves as they bounce back to their highly evolved ears.

There is emerging evidence that blind people can harness their sense of hearing – which is often more acute – to interpret reflected sound and create detailed mental images of their surroundings, including the distance, size and density of objects.

The technique is being piloted in Glasgow, where 10 children aged five to 17 are being taught by staff from Visibility, one of the city’s oldest charities for the blind. The children are learning how to make the clicking sound and how to use the technique even in noisy urban areas, including the underground system.

Blind people in America, where human echolocation was pioneered, have learnt to differentiate between people, trees, buildings and parked cars by interpreting the pitch and timbre of the echo they produce. Practitioners say they can determine the height, density and shape of objects up to 100ft away.

People using echolocation can determine the distance they are from an object by the length of time it takes for the sound to travel back. Its position can be established by whether the echo hits the left or right ear first. The size of an object can be determined by the intensity of the echo. A smaller object reflects less of the sound wave. The object’s direction of movement can be established by the pitch of the echo, which is lower if it is moving away from the source.