The role of the sound of tapping for nonvisual judgment of gap crossability.

The author investigated the possibility that nonvisual locomotion with a cane depends on the sound of the cane tapping. Blindfolded participants were asked to judge whether a gap in front of them could be crossed by walking. An acoustic analysis suggested that sound could, in theory, distinguish the gaps. Blindfolded sighted participants in Experiments 1 and 2 judged crossability under conditions in which only the sound of tapping was available and in which the sound was minimized; the third and fourth experiments included experienced cane users. Both inexperienced observers and experienced cane users were unaffected by sound reduction and were less able to discriminate gaps when using sound only than when using reduced sound. A fifth experiment indicated that active-passive differences were not responsible for these effects. Results indicate that sound is not necessary or sufficient for judging nonvisible crossability with a probe.