Psychoacoustical Study of Some Factors Affecting Human Echolocation

Abstract

Echolocation systems similar to those employed by bats are often considered as possible mobility aids for the blind. Echo sound fields would probably provide abundant environmental information if the human auditory system could effectively detect and locate echolike sounds. The refractory nature of the auditory system, however, enables the direct sound from an echolocation sound source to mask the echoes. A series of experiments was designed to investigate this masking phenomenon. In these experiments, both the direct and echo sounds were simulated by binaural clicks presented through earphones. The results indicate that localization judgments are affected by echo-delay time, relative intensity of the echo pulse and the direct sound pulse, and interaural time delay in the direct sound pulse. Sound-intensity level and repetition rate have little effect. Localization errors produced by interaural time delay in the direct pulse indicate that the pulse generator should be positioned on the centerline of the subject's head. This provides an explanation for the failure of echolocation systems employing hand-held sources, and indicates that with a head-mounted sound source human echolocation may become feasible for blind guidance. [This work was supported in part by the U. S. Army, the U. S. Air Force Office of Scientific Research, and the U. S. Office of Naval Research; in part by the National Science Foundation (Grant G-16526); in part by the National Institutes of Health (Grant MH-04737-02).]