The problem of designing an auditory display for a binaural mobility aid for the blind is investigated. The basis for the project was the binaural linear F.M. echolocation mobility aid proposed by Prof. L. Kay. The sciences of engineering and psychophysics are freely intermixed to define the optimal form of the azimuthal dimension of an auditory spatial display".

It is shown that to take advantage of the frequency domain range coding it is necessary to use interaural amplitude difference (IAD) as the localization cue. A series of experiments confirmed this and suggested a modification to the system concept.

An extensive psychophysical investigation of auditory localization with IAD determined the parametric-form of the localization function, from which the azimuthal dimension of the display was specified and analysed. The problem of generating this display from an echolocation system is discussed.

Measures of the resolution capability of the auditory system in a static. Two object environment are presented. A computer simulation of the auditory display was used to justify the use of data derived from dichotic experiments to specify a display for use with head movement. Adaptive strategies for estimating the localization function are described.