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The Indo-Pacific humpback dolphins (Sousa chinensis) are nearshore odontocetes, distributed in tropical and sub-tropical oceans. This species has been studied to unveil its ability to echolocate. Indo-Pacific humpback dolphin, like its Odontocetes companion, relies on echolocation system to navigate and detect targets, which contains a sound transmitting system in the forehead and a sound reception in the jaw. Their soft tissues present gradient sound speed and density distributions in the forehead. Solid skull, air structures and soft tissues form a natural multi-phase meta-material to modulate sounds into energy focused beams. This multi-phase property is also applied to the hearing system as revealed in current papers. Here in this work, the physical mechanism of sound reception in the Indo-Pacific humpback dolphin is studied by using the computed tomography (CT) scanning, physical measurements and numerical simulation. Hounsfield units (HUs) of the forehead tissues are extracted from CT scanning results. A linear relationship is revealed between HU and sound speed, HU and density, which are combined with HU distribution to reconstruct the sound speed and density distribution of the sound reception system. The CT scanning shows that the sound reception system located at lower head is composed of external mandibular fat, internal mandibular fat, mandible and hearing bones. Model of sound reception system is developed on the basis of CT scanning results and used in subsequent simulations. The physical process of sound reception reveals that the hearing system can guide sounds through variable pathways to reach hearing bones. Sounds can enter into the reception system along the acoustic pathways composed of mandible, external mandibular fat and internal mandibular fat. Mandibular fat and mandible form a unique sound pathway. In addition, another pathway which is composed of external mandibular fat, pan bone and internal mandibular fat can lead the sound to propagate and finally arrive at hearing bones. The diversity of acoustic pathways is applicable to a range of frequencies from 30 to 120 kHz. The variability of acoustic pathways in Indo-Pacific humpback dolphin shows the complexity of its biosonar system. The anatomy and simulation results can deepen our understanding of the mechanism of echolocation of Indo-Pacific humpback dolphin and provide references for designing man-made sound reception devices.
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Keywords:
- Indo-Pacific humpback dolphin /
- sound reception /
- bioacoustics /
- acoustic fat
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Wang X Y, Miao X, Wu F X, Yan C X, Liu W H, Zhu Q 2012 J. Oceanogr. Taiwan Strait 31 225Google Scholar
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Wang D, Wang K X, Liu R J, Chen P X, Shen G, Wang Z F, Lu W X, Yang S Z 1989 Nat. Sci. J. Xiangtan Univ. 2 116
[28] 肖友芙, 王丁, 王克雄 1993 海洋学报 15 125
Xiao Y F, Wang D, Wang K X 1993 Acta Oceanolog. Sin. 15 125
[29] 王丁, 王克雄, 刘仁俊, 谌刚, 卢文祥 1988 华中理工大学学报 3 55
Wang D, Wang K X, Liu R J, Shen G, Lu W X 1988 J. Huazhong Univ. Sci. Tech. 3 55
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图 2 中华海豚头部声接收系统不同截面的声速、密度分布 (a) 水平截面(xz)声速分布; (b) 垂直截面(yz)声速分布; (c) 水平截面(xz)密度分布; (d) 垂直截面(yz)密度分布
Figure 2. Distributions of sound speed and density in different planes of reception system in Indo-Pacific humpback dolphin: (a) Sound speed distribution in horizontal plane; (b) sound speed distribution in vertical plane; (c) density distribution in horizontal plane; (d) density distribution in vertical plane.
图 3 中华白海豚不同截面声接收模型网格划分 (a) 水平截面计算域; (b) 垂直截面计算域; (c) 头部水平截面声接收系统; (d) 头部垂直截面声接收系统
Figure 3. Meshing of sound reception models in different planes: (a) Computing domain in horizontal plane; (b) computing domain in vertical plane; (c) sound reception system in horizontal plane; (d) sound reception system in vertical plane.
图 7 无指向性的单频声波从0°入射中华白海豚声接收系统不同截面的稳态声场 水平截面: (a) 30 kHz, (b) 60 kHz, (c) 120 kHz; 垂直截面: (d) 30 kHz, (e) 60 kHz, (f) 120 kHz
Figure 7. The sound field of omnidirectional single-frequency sound waves with an incident angle of 0° in different sections directionless single-frequency sound waves. Horizontal section: (a) 30 kHz, (b) 60 kHz, (c) 120 kHz; vertical section: (d) 30 kHz, (e) 60 kHz, (f) 120 kHz.
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[1] Au W W L 1993 The Sonar of Dolphins (New York: Springer-Verlag) pp1−21
[2] Jefferson T A, Hung S K 2004 Aquat. Mamm. 30 149Google Scholar
[3] Van Parijs S M, Corkeron P J 2001 J. Mar. Biol. Assoc. U. K. 81 533Google Scholar
[4] 王先艳, 妙星, 吴福星, 闫晨曦, 刘文华, 祝茜 2012 台湾海峡 31 225Google Scholar
Wang X Y, Miao X, Wu F X, Yan C X, Liu W H, Zhu Q 2012 J. Oceanogr. Taiwan Strait 31 225Google Scholar
[5] 刘文华, 黄宗国 2000 海洋学报 22 95Google Scholar
Liu W H, Huang Z G 2000 Acta Oceanolog. Sin. 22 95Google Scholar
[6] Chen B Y, Zheng D M, Ju J F, Xu X R, Zhou K Y, Yang G 2011 Zool. Stud. 50 751
[7] Li S H 2020 Science 367 1313Google Scholar
[8] Fang L, Wu Y P, Wang K X, Pine M K, Wang D, Li S 2017 J. Acoust. Soc. Am. 142 771Google Scholar
[9] Fang L, Li S H, Wang K X, Wang Z T, Shi W J, Wang D 2015 J. Acoust. Soc. Am. 138 1346Google Scholar
[10] Wang Z T, Fang L, Shi W J, Wang K X, Wang D 2013 J. Acoust. Soc. Am. 133 2479Google Scholar
[11] Song Z C, Zhang Y, Wang X Y, Wei C 2017 J. Acoust. Soc. Am. 142 EL381Google Scholar
[12] Zhang Y, Song Z C, Wang X Y, Cao W W, Au W W L 2017 Phys. Rev. Appl. 8 064002Google Scholar
[13] Song Z C, Zhang Yu, Berggren P, Wei C 2017 J. Acoust. Soc. Am. 141 681Google Scholar
[14] Song Z C, Zhang Yu, Wang X Y 2018 Europhys. Lett. 124 64004Google Scholar
[15] Song Z C, Zhang Y, Mooney T A, Wang X Y, Smith A B, Xu X H 2019 Bioinspiration Boimimetics 14 016004Google Scholar
[16] Purves P E, Pilleri G E 1983 Echolocation in Whales and Dolphins (London: Academic Press) pp1−631
[17] Purves P E 1996 Anatomy and Physiology of the Outer and Middle Ear in Cetaceans In Whales, Dolphins, and Porpoises (Berkeley: University of California Press) pp321−380
[18] Norris K S 1968 The Evolution of Acoustic Mechanisms in Odontocete Cetaceans in Evolution and Environment (New Haven: Yale University Press) pp297−324
[19] Bullock T H, Grinnell A D, Ikezono E, Kameda K, Katsuki J, Nomota M, Sato O, Suga N, Yanagisawa K 1968 Z. Vergleichende Physiol. 59 117
[20] McCormick J G, Wever E G, Palin J 1970 J. Acoust. Soc. Am. 48 1418Google Scholar
[21] Brill R L, Sevenich M L, Sullivan T J, Sustman J D, Witt R E 1988 Mar. Mammal Sci. 4 223Google Scholar
[22] Varanasi U S, Malins D C 1970 Biochemistry 9 4576Google Scholar
[23] Cranford T W, McKenna M F, Soldevilla M S, Wiggins S M, Goldbogen J A, Shadwick R E, Krysl P, Leger J A S, Hildebrand J A 2008 Anat. Rec. 291 353Google Scholar
[24] Cranford T W, Krysl P, Hildebrand J A 2008 Bioinspir. Boimim. 3 016001Google Scholar
[25] Aroyan J L 2001 J. Acoust. Soc. Am. 110 3305Google Scholar
[26] Ketten D R 2000 Cetacean Ears In Hearing by Whales and Dolphins (New York: Springer) pp43−108
[27] 王丁, 王克雄, 刘仁俊, 陈佩薰, 谌刚, 王治藩, 卢文祥, 杨叔子 1989 湘潭大学自然科学学报 2 116
Wang D, Wang K X, Liu R J, Chen P X, Shen G, Wang Z F, Lu W X, Yang S Z 1989 Nat. Sci. J. Xiangtan Univ. 2 116
[28] 肖友芙, 王丁, 王克雄 1993 海洋学报 15 125
Xiao Y F, Wang D, Wang K X 1993 Acta Oceanolog. Sin. 15 125
[29] 王丁, 王克雄, 刘仁俊, 谌刚, 卢文祥 1988 华中理工大学学报 3 55
Wang D, Wang K X, Liu R J, Shen G, Lu W X 1988 J. Huazhong Univ. Sci. Tech. 3 55
[30] Li S H, Wang D, Wang K X, Taylor E A, Cros E, Shi W J, Wang Z T, Fang L, Chen Y F, Kong F 2012 J. Exp. Biol. 215 3055Google Scholar
[31] Wei C, Zhang Y, Au W W L 2014 J. Acoust. Soc. Am. 136 423Google Scholar
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