Mechanical Sound Sources for Obstacle Perception by Audition

Abstract

Two simple devices of the type mentioned in the title will be discussed. Each consists essentially of a cup-sized parabaloidal plastic reflector with a vibrator in the focal plane. The first type, similar to one developed by D. R. Griffin at Cornell, employs a dented flat steel spring and produces loud broad-band high frequency clicks when triggered. The second employs a miniature reed whistle and produces several different high frequency squeaks (depending on how a rubber bulb built into the horn is manipulated). Preliminary tests with four subjects indicate the following: The first type produces sufficient sound for distinct echoes to be returned from distant objects outdoors but is too loud for indoor use; the second type is useful indoors up to a far point of 5–20 feet (depending on ambient noise), giving rise to essentially the same sort of cues obtained with the continuous wave electronic models employed previously.