Mathematics of two-microphone sound localization using ITDs and motion

What is it about?

Sound localization is one of the key processes for the survival of any higher animal. There have been many attempts to analyze and understand the mechanisms of this process in the context of its implementation into robots. The focus of our contribution lies on the mathematical description of the variations of Interaural Time Delay (ITD), which constitute essential cues in the case of motion in combination with a binaural system. Our work establishes the equivalence between these variations and the binaural Doppler effect. Furthermore, we show that sound localization in three dimensions can be easily deduced from measurements of ITDs and rotation speed. Theory is illustrated with an experimental part.

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Why is it important?

The mathematical developments might throw some light on the fact that Nature put the auditory and the vestibular systems in mammals in physical proximity. Motion provides essential information about localization of the body in space. More particularly, the effects of head movements are noticed by the vestibular system. Together with the perception of ITDs, this information helps the animal identify its position in space relative to a sound source (foe or prey). The understanding of the fundamentals of the dynamic sound localization process is useful for the development of robots, which start entering our physical environment. One problem to solve in this context is the dynamic acoustic localization of persons, animals and machines in their roles as obstacles, dangers or targets.

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