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Modeling whale audiograms: effects of bone mass on high-frequency hearing
S Hemilä1, S Nummela, T Reuter
1Laboratory of Physics, Helsinki University of Technology, Espoo, Finland.
Hearing Research
|December 22, 2000
Summary
A mechanical model of the toothed whale middle ear accurately predicts hearing ranges. Ossicular mass is identified as a key factor limiting high-frequency hearing in toothed whales and other mammals.
Area of Science:
- Bioacoustics
- Mammalian Physiology
- Comparative Anatomy
Background:
- A previous study developed a mechanical model of the toothed whale middle ear using species-specific anatomical data.
- This model successfully predicted behavioral audiograms for five out of six odontocete species.
Purpose of the Study:
- To re-evaluate the mechanical model with new data for the killer whale (Orcinus orca).
- To investigate the relationship between middle ear size, ossicular mass, and hearing frequency limits in odontocetes.
Main Methods:
- Utilized new published audiogram data for the killer whale.
- Applied a four-bone mechanical model to analyze the killer whale's auditory capabilities.
- Investigated the effect of isometric scaling and ossicular mass on audiogram characteristics across different species.
Main Results:
- New data indicate the previous killer whale audiogram was from a specimen with impaired high-frequency hearing.
- A revised audiogram for the killer whale aligns with the mechanical model and other odontocete audiograms.
- Audiograms of different toothed whale species become similar after scaling by a factor related to ossicular mass (1/m^3).
Conclusions:
- The mechanical model, considering ossicular mass, accurately predicts high-frequency hearing limits in toothed whales.
- Ossicular mass is a critical determinant of high-frequency hearing sensitivity in toothed whales, analogous to terrestrial mammals.