Finding the direction of a sound

It is believed that many animals determine the direction of a low frequency sound by comparing the times at which the sound arrives at its ears. Some years ago Jeffress proposed that this is accomplished by a network of coincidence detection neurons together with a system of delay line-like axons connecting these neurons to the two ears. There is substantial experimental evidence in favor of many aspects of this model, although some recent experiments, particularly in mammals, seem to be at odds with certain aspects of the Jeffress picture. We point out that from an engineering standpoint the original Jeffress approach to coincidence detection is not a very efficient way to accomplish sound localization. Recent experiments which seem difficult to reconcile with the Jeffress picture, might be understood in terms of a different coincidence detection scheme. 1 I. INTRODUCTION AND BACKGROUND The problem of how an animal determines the direction of a sound has been discussed and studied for many years. Lord Rayleigh (1907) pointed out that for low frequency sounds, directional information is contained in the difference in the phases of the sound waves a