Dept. of Physics, East Carolina University, Greenville, NC, United States of America.
Dept. of Biology, Virginia Commonwealth University, Richmond, VA, United States of America.
PLoS One. 2022 Jul 12;17(7):e0267338. doi: 10.1371/journal.pone.0267338. eCollection 2022.
Although the continental slope and abyss comprise the largest habitat on earth, the absence of documented fish sounds from deep waters is striking. Fishes with sexually dimorphic muscles attached to their swim bladders suggests that sounds are likely used in male courtship on the upper, mid and lower continental slope. To investigate the effects of environmental extremes on fish sound production, the acoustic behavior of a driven bubble is examined. This study is also relevant to target strength of sonar returns from fish and hearing in auditory specialist fishes. A bubble is a classic, if imperfect, model for swim bladder behavior since the swim-bladder wall is an anisotropic viscoelastic structure responsible for rapid damping. Acoustic properties of bubbles-including far-field resonant frequency, damping factor, and quality factor-are calculated in warm and cold surface conditions and in cold deep-water (depths 1000 m, 2000 m, and 3500 m) conditions using parameters for oxygen and nitrogen, the dominant gases in swim bladders. The far-field resonant frequency and damping factor of a bubble increase with depth, and the scattering cross-section and quality factor decrease with depth. These acoustic properties scale with undamped oscillation frequency of the bubble and do not vary significantly due to gas type or temperature. Bubbles in the deep-water environments are much less efficient radiators of sound than bubbles near the surface because the far-field radiated power for the same excitation decreases with depth. A bubble at depth 3500 m has a 25 dB loss in radiated sound power compared to the same-radius bubble at the surface. This reduction of radiation efficiency in deep water likely contributes to the absence of fish sound recordings in those environments.
尽管大陆坡和深海深渊构成了地球上最大的栖息地，但深水中没有记录到鱼类声音却引人注目。具有性二态肌肉的鱼类附着在它们的鳔上，这表明声音可能在大陆坡的上部、中部和下部用于雄性求偶。为了研究环境极端对鱼类发声的影响，研究了驱动气泡的声学行为。本研究还与声纳回波的鱼类目标强度和听觉特化鱼类的听觉有关。气泡是鳔行为的经典模型（尽管不完美），因为鳔壁是一种各向异性粘弹性结构，负责快速阻尼。使用鳔中占主导地位的氧气和氮气的参数，计算了包括远场共振频率、阻尼因子和品质因数在内的气泡的声学特性，这些参数在温暖和寒冷的表面条件以及寒冷的深海条件（深度为 1000m、2000m 和 3500m）下。气泡的远场共振频率和阻尼因子随深度增加而增加，散射截面和品质因数随深度减小。这些声学特性与未阻尼气泡的振荡频率相关，与气体类型或温度无关，变化不大。由于相同激励下的远场辐射功率随深度减小，深海环境中的气泡比近地表的气泡作为声音辐射体的效率低得多。与同一半径的表面气泡相比，深度为 3500m 的气泡在辐射声功率方面损失了 25dB。深海中这种辐射效率的降低可能是这些环境中缺乏鱼类声音记录的原因之一。
