HUMAN ECHOLOCATION USING CLICK TRAINS AND CONTINUOUS NOISE

Blind people may detect objects from the information in reflected sounds, echolocation. Detection as a function of the number of clicks compared to a continuous noise was tested by presenting clicks of 5 ms with rates from 1 to 64 clicks during a 500 ms period and a 500-ms continuous white noise. The sounds were recorded in an ordinary room through an artificial binaural head. The reflecting object was an aluminum disk, diameter 0.5 m, at distances of 1 and 1.5 m. These sounds were later presented to 3 blind and 16 sighted participants in a laboratory using a 2AFC methodology. The task was to detect which of the two sounds that contained a reflecting object. Feedback was provided. The blind participants had a higher detection than the sighted, but there were also differences among the blind. These results are put in relation to physical features such as the autocorrelation function and spectral variations. Blind people use sounds to find out how the world around them is constituted. One source of information is the direct sounds emitted by sound source