Implementation and Evaluation of Auditory Models for Human Echolocation

Blind people use echoes to detect objects and to find their way, the ability being known as human echolocation. Previous research have found some of the favorable conditions for the detection of the object, with many factors yet to be analyzed and quantified. Studies have also shown that blind people are more efficient than the sighted in echolocating, with the performance varying among the individuals. This motivated the research in human echolocation to move in a new direction to get a fuller understanding for the high detection of the blind. The psychoacoustic experiments solely cannot determine how the superior echo detection of the blind listeners should be attributed to perceptual or physiological causes. Along with the perceptual results it is vital to know how the sounds are processed in the auditory system. Hearing research has led to the development of several auditory models by combining the physiological and psychological results with signal analysis methods. These models try to describe how the auditory system processes the signals. Hence, to analyze how the sounds are processed for the high detection of the blind, auditory models available in the literature were used in this thesis. The results suggest that repetition pitch is useful at shorter distances and is determined from the peaks in the temporal profile of the autocorrelation function computed on the neural activity pattern. Loudness attribute also plays a role in providing information for the listeners to echolocate at shorter distances. At longer distances timbre aspects such as sharpness information might be used by the listeners to detect the objects. It was also found that the repetition pitch, loudness and sharpness attributes in turn depend on the room acoustics and type of the stimuli used. These results show the fruitfulness of combining results from different disciplines through a mathematical framework given by signal analysis.