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. 2019 Jul 22;6(5):921–928. doi: 10.1093/nsr/nwz085

Figure 1.

Figure 1.

Design of PPM device. (A) Image of a finless porpoise. (B) Computed tomography imaging of the porpoise, where I, II, III, IV, and V correspond to melon, muscle, connective tissue, skull, and air sacs, respectively. (C) Sound velocity distributions of melon, muscle, and connective tissues. (D) Schematic illustration of the fabrications of air structure, steel maxilla, and hybrid metamaterials. Melon, muscle, and connective tissue were mimicked by using a steel cylinder array with φ = 0.44, an aluminum cylinder array with φ = 0.62, and a steel cylinder array with φ = 0.66, respectively. (E) Assembly of the PPM device. (F) Acoustic beam formations of a model with air component V, a model with V and solid structure IV, and the PPM model with I, II, III, IV, and V, where frequency 30 kHz was used.