Special acoustical role of pinna simplifying spatial target localization by the brown long-eared bat Plecotus auritus

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Special acoustical role of pinna simplifying spatial target localization by the brown long-eared bat Plecotus auritus

Xin Ma, Sen Zhang, Zheng Dong, Hongwang Lu, Jinke Li, and Weidong Zhou

Phys. Rev. E 102, 040401(R) – Published 15 October 2020

Abstract

Echolocating bats locate a target by sonar. The performance of this system is related to the shape of the binaural conformation in bats. From numerical predictions, it was found that in a central frequency band, the orientation of a strong sidelobe is shifted nearly linearly in the vertical direction. Inspired by this, the authors built an accurate wide-scope elevation estimation system by constructing a pair of erect artificial pinnae and realized simultaneous elevation and azimuth estimation by constructing a pair of orthogonal pinnae. By demonstrating the simplicity of spatial target echolocation, the authors showed that only two independent single-output neural networks were needed for either elevation or azimuth estimation. This method could be applied to imitate any other mammal species with similar pinna directivity patterns to facilitate and improve an artificial echolocation system.

Received 27 May 2020
Revised 24 August 2020
Accepted 29 September 2020

DOI:https://doi.org/10.1103/PhysRevE.102.040401

Physics Subject Headings (PhySH)

Bioacoustics Sound detection

General Physics

Authors & Affiliations

Xin Ma ^1,2,*, Sen Zhang¹, Zheng Dong¹, Hongwang Lu³, Jinke Li⁴, and Weidong Zhou^5,*

¹School of Information Science and Engineering, Shandong University, Qingdao, Shandong 266237, China
²Shenzhen Research Institute, Shandong University, Shenzhen, Guangdong 518057, China
³School of Physics, Shandong University, Jinan, Shandong 250100, China
⁴Department of Mathematics, University of Kansas, Lawrence, Kansas 66045, USA
⁵School of Microelectronics, Shandong University, Jinan, Shandong 250101, China

^*max@sdu.edu.cn; wdzhou@sdu.edu.cn

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Issue

Vol. 102, Iss. 4 — October 2020

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Images

Figure 1
Pinna of the brown long-eared bat and its aural spatial directivity: (a) an outline of a pinna model from the brown long-eared bat; (b) aural spatial directivity pattern visualized by three-dimensional isosurfaces of beam gain; (c) $- 3$ dB contours of a ventral sidelobe (first sidelobe), which performs a frequency-driven scan in the band from 34 to 60 kHz. The scale bar here also applies to the isosurface blobs (b).
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Figure 2
Artificial parallel erect pinnae (a) and their ideal $- 3$ dB contours (b); artificial orthogonal pinnae (c) and their ideal $- 3$ dB contours (d).
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Figure 3
Definition of elevation angle (a) and locations of the target and device during training and testing; the elevation was changed by altering the height of the rubber ball used as the target. (b) The artificial batlike ear device was moved in turn to each of the eight locations (white circles) surrounding the spherical target to locate and obtain the data. The data obtained at each site served as test data, and the data obtained at other sites served as training data in the eightfold cross-validation experiments.
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Figure 4
Example of a signal emitted by the loudspeaker and echoes received by the two ears: (a), (b), (c) emitted signal and echoes received by left and right microphones; (d), (e), (f) spectrograms for the emitted signal and the echoes received by the left and right microphones.
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Figure 5
Single-pulse estimation results obtained by parallel erect pinnae. The horizontal axes of (a) and (b) represent the error boundaries for counting the estimated results. (a) The mean and standard deviation of cumulative distributions in the eight cross-validation cycles for elevation estimation. The different bar colors stand for different limited scopes ranging from $\pm 0^{\circ}$ to $\pm 90^{\circ}$ of azimuth for the data. (b) The mean and standard deviation of cumulative distributions in the eight cross-validation cycles for azimuth estimation. The data came from a unique limited scope in the vertical direction, which was $20^{\circ}$ to $55^{\circ}$ .
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Figure 6
Elevation and azimuth estimated with orthogonal pinnae: (a), (b) comparisons of the azimuth and elevation estimates in the single-pulse test with actual values; (c) joint cumulative distributions for the common errors of azimuth and elevation estimates under pulse trains with different numbers of observations; the abscissa axis represents the error constraint that both azimuth and elevation must meet simultaneously.
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