A model and experimental approach to the middle ear transfer function related to hearing in the humpback whale (Megaptera novaeangliae)

Abstract

At present, there are no direct measures of hearing for any baleen whale (Mysticeti). The most viable alternative to in vivo approaches to simulate the audiogram is through modeling outer, middle, and inner ear functions based on the anatomy and material properties of each component. This paper describes a finite element model of the middle ear for the humpback whale (Megaptera novaeangliae) to calculate the middle ear transfer function (METF) to determine acoustic energy transmission to the cochlea. The model was developed based on high resolution computed tomography imaging and direct anatomical measurements of the middle ear components for this mysticete species. Mechanical properties for the middle ear tissues were determined from experimental measurements and published values. The METF for the humpback whale predicted a better frequency range between approximately 15 Hz and 3 kHz or between 200 Hz and 9 kHz based on two potential stimulation locations. Experimental measures of the ossicular chain, tympanic membrane, and tympanic bone velocities showed frequency response characteristics consistent with the model. The predicted best sensitivity hearing ranges match well with known vocalizations of this species.