Ridgway S H, Carder D A, Kamolnick T, Smith R R, Schlundt C E, Elsberry W R
Marine Mammal Program, D35, PLBS, 53560 Hull Street, San Diego, CA 92152-5001, USA.
J Exp Biol. 2001 Nov;204(Pt 22):3829-41. doi: 10.1242/jeb.204.22.3829.
Hearing is attenuated in the aerial ear of humans and other land mammals tested in pressure chambers as a result of middle ear impedance changes that result from increased air density. We tested the hypothesis, based on recent middle ear models, that increasing the density of middle ear air at depth might attenuate whale hearing. Two white whales Delphinapterus leucas made dives to a platform at a depth of 5, 100, 200 or 300 m in the Pacific Ocean. During dives to station on the platform for up to 12 min, the whales whistled in response to 500 ms tones projected at random intervals to assess their hearing threshold at each depth. Analysis of response whistle spectra, whistle latency in response to tones and hearing thresholds showed that the increased hydrostatic pressure at depth changed each whale's whistle response at depth, but did not attenuate hearing overall. The finding that whale hearing is not attenuated at depth suggests that sound is conducted through the head tissues of the whale to the ear without requiring the usual ear drum/ossicular chain amplification of the aerial middle ear. These first ever hearing tests in the open ocean demonstrate that zones of audibility for human-made sounds are just as great throughout the depths to which these whales dive, or at least down to 300 m.
在压力舱中接受测试的人类及其他陆地哺乳动物的气导耳听力会减弱，这是由于空气密度增加导致中耳阻抗变化所致。基于近期的中耳模型，我们测试了这样一个假设：在深海中增加中耳空气密度可能会减弱鲸鱼的听力。两头白鲸（白鲸属）潜入太平洋中5米、100米、200米或300米深处的一个平台。在潜入平台并停留长达12分钟的过程中，鲸鱼会对以随机间隔投射的500毫秒音调发出鸣叫，以评估它们在每个深度的听力阈值。对反应鸣叫频谱、对音调的鸣叫潜伏期和听力阈值的分析表明，深度增加带来的静水压力变化改变了每头鲸鱼在深度处的鸣叫反应，但并未总体上减弱听力。鲸鱼听力在深度处未减弱这一发现表明，声音是通过鲸鱼的头部组织传导至耳朵的，而无需像气导中耳那样通过通常的鼓膜/听小骨链放大。这些首次在公海中进行的听力测试表明，人造声音的可听区域在这些鲸鱼潜入的整个深度范围内，或者至少在300米深度内，同样广阔。
