Cunningham Kane A, Reichmuth Colleen
Department of Ocean Sciences, Long Marine Laboratory, University of California, Santa Cruz, 100 Shaffer Road, Santa Cruz, CA 95060, USA.
Institute of Marine Sciences, Long Marine Laboratory, University of California, Santa Cruz, Santa Cruz, CA 95060, USA.
Hear Res. 2016 Jan;331:83-91. doi: 10.1016/j.heares.2015.10.002. Epub 2015 Oct 28.
Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism.
现有证据表明，一些鳍足类动物（海豹、海狮和海象）能够探测到远高于其物种传统高频听力极限的水下声音。然而，这一现象尚未得到充分研究：超出传统高频极限频率的灵敏度模式尚未得到很好的解析，而且介导这些频率听力的听觉机制的性质也不清楚。在本研究的第一部分，对一只加州海狮（加利福尼亚海狗）、一只港海豹（港海豹）和一只斑海豹（斑海豹）在50 - 180千赫范围内的听觉灵敏度模式进行了测量。结果显示，所有三个受试对象的听力图高频端都存在两个明显的斜率区域。第一个区域的特征是灵敏度随频率增加而迅速下降，即斜率陡峭，随后是灵敏度下降不太迅速的区域，即斜率较浅。在本研究的第二部分，进行了一项掩蔽实验，以研究一只港海豹受试对象的基底膜对以140千赫为中心的窄带掩蔽噪声的声能是如何反应的。测量到的掩蔽模式表明,受试对象听力图高频端灵敏度最初的迅速下降并非如先前假设的那样是由于耳蜗限制，而是由于传导机制的限制。
