Directional hearing or binaural phenomenon?

Abstract

Binaural phenomenon is known to be responsible for sound localization in humans. A similar mechanism is thought to provide the dolphin with the ability to localize targets and sound source. At the same time, the dolphin possesses quite good directional hearing, let alone very directional click transmission, which is absent in humans. The directional hearing in the dolphin, at least in the horizontal plane, appears to be consistent with two ears’ reception. Does it signify that the binaural phenomenon coexists in dolphins with directional hearing? As far as humans are concerned, the spatial hearing does not involve any substantial hearing directionality. The directionality seems to negate the main advantage of the binaural hearing, that is instantaneous determination of a sound source direction, and complicate the use of binaural cues. It was found that the lesser intensity of high-frequency clicks the smaller an angle between their sources should be for the dolphin to hear them simultaneously. The directivity pattern of the dolphin’s auditory system was measured as a dependence of the threshold angle between the sources on the click’s intensity. At high frequencies, the dolphin’s auditory system performed as a directional system rather than an omnidirectional binaural system known for humans.