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Sound-diffracting flap in the ear of a bat generates spatial information
Rolf Müller1, Hongwang Lu, John R Buck
1School of Physics and Microelectronics, Shandong University, Hongjia Lou 5, 250100 Jinan, China. mueller@sdu.edu.cn
Physical Review Letters
|March 21, 2008
Summary
Sound diffraction by the ear provides directional cues. A bat
Area of Science:
- Bioacoustics
- Auditory Neuroscience
- Mammalian Sensory Systems
Background:
- Sound diffraction by the external ear (pinna) is a known source of auditory directional information.
- Quantifying the precise information content derived from pinna morphology has been challenging.
Purpose of the Study:
- To develop and apply a numerical method for quantifying sound-based directional information generated by the mammalian ear.
- To investigate the contribution of specific pinna structures, like a bat's flap, to auditory spatial awareness.
Main Methods:
- Utilized numerical predictions to quantify sound diffraction patterns.
- Employed the Cramér-Rao lower bound as an information measure.
- Analyzed the directivity patterns of sound pressure levels.
Main Results:
- A numerical approach successfully quantified directional information from sound diffraction.
- A small flap on a bat's pinna significantly increased the solid angle of directional information.
- The presence of the flap more than doubled the directional information capacity in a specific frequency band.
Conclusions:
- Physical ear shape is directly linked to sensory information through frequency-dependent directivity patterns.
- The developed method allows for the quantification of pinna contributions to directional hearing.
- This approach facilitates interspecific comparisons of auditory spatial processing in mammals.
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