The effects of mechanical property manipulation on Minke Whale hearing sensitivity

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TitleThe effects of mechanical property manipulation on Minke Whale hearing sensitivity
Publication TypeConference Paper
Year of Publication2011
AuthorsTubelli, A. A., A. L. Zosuls, D. R. Ketten, and D. C. Mountain
Conference Name19th Biennial Conference on the Biology of Marine Mammals
Pagination296-297
Date Published11
PublisherSociety for Marine Mammology
Conference LocationTampa, FL
Keywordsbiomechanics, hearing, hearing models, hearing sensitivity, mechanical property manipulation, middle ear, minke whale, mysticetes
AbstractThere is little knowledge about the biomechanics of hearing in mysticetes. Biophysical models of the middle ear can predict audiograms in part via the middle-ear transfer function.
Full TextThere is little knowledge about the biomechanics of hearing in mysticetes. Biophysical models of the middle ear can predict audiograms in part via the middle-ear transfer function. Previous work predicted that the frequency range of best sensitivity for the Minke Whale (Balaenoptera acutorostrata) is near the range of vocalizations for that species. A revised middle ear finite element model incorporates middle ear soft tissues as geometry, including the glove finger, the ear drum homologue familiar from terrestrial mammalian species. Since the mechanical properties of cetacean tissue have not been measured extensively, mechanical properties of human tissue were used in the model. In this study, we measure the sensitivity of the minke middle ear model to changes in those mechanical properties. Results show that increasing the Young's modulus of the annular ligament causes the transfer function to decrease in the middle and lower frequencies. Increasing any other parameter by up to two orders of magnitude changed the transfer function by less than 10%. Since input of sound to the middle ear is not well understood, the location of the incident pressure was also moved to determine the effect on the transfer function. The two areas tested were the tip of the glove finger and the area of attachment of the fat pad to the tympanic bone. Pressure at the tympanic plate resulted in the transfer function magnitude being one order of magnitude greater than pressure applied to the glove finger. The tympanic plate input also resulted in a remarkably higher bandwidth for the best sensitivity region of the transfer function; the high-frequency cutoff moved from 2 kHz to 60 kHz. The low-frequency cutoff remained the same. Assuming minimal impedance mismatch, the model shows it is possible that the fats could play a role in sound transmission. Supported by OPNAV Environmental Division.