Comparison of obstacle sense ability between the blind and the sighted: A basic psychophysical study for designs of acoustic assistive devices

Abstract

The ability by which the blind can recognize objects around them solely by hearing is called “obstacle sense.” By analyzing and modeling the mechanism of this sense, the resultant model could be utilized in new concepts for blind mobility aids as well as training methods. In this paper, we first conducted a comparative experiment regarding coloration perception between the blind and the sighted. In the experiment, subjects are asked to answer whether two successive sounds with a different dip-to-dip interval are perceived to be same by means of two alternative forced choices. The results show no significant difference in discrimination between the two groups; the blind and the sighted. Next, “impressions” elicited by the sounds with various dip-to-dip intervals are analyzed on the two groups using the Semantic Differential Method (SDM). The results indicate that the sighted tend to focus mainly on the quantitatively represented changes such as pitch and loudness of the sounds, while the blind are inclined to focus not only on the quantitative sound change, but also on qualitative impressions in the sound changes. Since it is assumed that the qualitative impressions are related to distances of the obstacles from the blind, third, we carry out a comparative experiment regarding the obstacle-distance perception. The result indicates that the blind can more exactly answer the obstacle-distance than the sighted. From the results of the three experiments and past studies, we discuss whether the obstacle sense is formed in the peripheral process or in the central process of the auditory nervous system, and then we propose new concepts for blind mobility aids as well as the obstacle sense training method.