On acoustic attenuation by swimbladder fish

This letter presents a theoretical study of sound attenuation by swimbladder fish. Since the sound attenuation is related to the sound extinction cross section, the focus of the letter is on theoretical calculation of the extinction cross section of swimbladder fish. A forward scattering theorem is used for the purpose. Based on simple scattering models for swimbladder fish, the frequency dependence of the extinction cross section is obtained. The result shows that while the air-filled swimbladder dominates the forward scattering of sound at low frequencies, the fish body may dominate the forward scattering in the high-frequency range. Without fitting parameters, the theoretical results compare favorably with some existing experimental data.