Morphology and Some Hearing Mechanisms of the External Ears of Bottlenose Dolphin (Tursiops truncatus) and Human Ears

Abstract

A comparative analysis has been performed on the morphology and some hearing mechanisms of the evolutionary new external ears of bottlenose dolphin (Tursiops truncatus) and human ears. It has been established that the role of external hearing canals in dolphins is played by corresponding mental foramens (MF), mandibular canals (MC), and soft tissues (ST) filling them. It has been demonstrated that the hearing canals of dolphins are maximally ported out to the tip of the rostrum towards echos and sounds reflected from underwater objects, in contrast to the hearing canals of humans, which are located on the left and right sides of the head. The major factors influencing the mechanisms of the formation of unique features in the spatial sound localization of dolphins are asymmetry in the architecture of their hearing canals, rostrum, and skull. However, for humans, these mechanisms are caused by the symmetric location of hearing canals on the left and right sides of the head. The morphology of the external ears of dolphins is adapted to utilize the destructive interference of reflected coherent interferences with the purpose of improving the signal/reflected interferences ratio. In general, the specific features of dolphin and human hearing cause fundamental distinctions in the morphology and auditory mechanisms of their external ears.