Obstacle Detection using Ambient or Self-generated Noise

Abstract

OBJECT ranging can be achieved by humans using the sound reflected or scattered from obstacles. For a range of wave-lengths short compared with the size of its surfaces, and long compared with the size of the irregularities in these surfaces, specular reflexion will be obtained and an acoustic image of the sound source will be formed analogous to an optical image. In many situations, however, such as the approach of an external corner, an acoustic image may not be audible from the observer's position. In these cases sound scattered from the edges and irregularities may, or frequently may not, give the necessary warning. Such signals are, however, weak compared with those of the acoustic image with which we are chiefly concerned.