ABSTRACT
Most of us have heard echoes across a deep mountain valley, down an empty street, or in a large hall. Indeed, concert halls need to be specially designed to avoid echoes from walls and ceilings interfering with the performance. Most people, however, pay little attention to more common, but less dramatic, echoes from tables, chairs, walls, and other objects encountered daily, possibly because we suppress this usually unimportant information. Although some animals, including bats and porpoises, are known to use echoes of sounds they emit in order to locate and identify all sorts of objects, we know relatively little about human use of such techniques. Given our usual reliance on vision for object and space perception, it would be interesting to know the extent to which we are able to use echo-location.
