Kastelein R A, Mosterd P, van Santen B, Hagedoorn M, de Haan D
Harderwijk Marine Mammal Park, The Netherlands.
J Acoust Soc Am. 2002 Nov;112(5 Pt 1):2173-82. doi: 10.1121/1.1508783.
The underwater hearing sensitivity of an 18-year-old male Pacific walrus was measured in a pool by using a go/no-go response paradigm and the up-down staircase method. Auditory sensitivity was measured using narrow-band, frequency-modulated signals (1500 ms duration) with center frequencies ranging from 0.125 to 15 kHz. The resulting underwater audiogram (50% detection thresholds) for this individual walrus shows the typical mammalian U-shape. Maximum sensitivity (67 dB re 1 microPa) occurred at 12 kHz. The range of best hearing (10 dB from the maximum sensitivity) was from 1 to 12 kHz. Sensitivity fell gradually below 1 kHz and dropped off sharply above 12 kHz. The animal showed a peculiar insensitivity for 2 kHz signals. His much higher sensitivity for 1.5- and 3-kHz signals indicated that this is a narrow-band phenomenon. Walrus hearing is relatively sensitive to low frequency sound, thus the species is likely to be susceptible to anthropogenic noise. The thresholds found during a small test with four frequencies with signal durations of 300 ms did not differ significantly from those obtained with signal durations of 1500 ms.
通过使用“是/否”反应范式和上下阶梯法，在一个水池中测量了一头18岁雄性太平洋海象的水下听觉敏感度。使用中心频率范围为0.125至15千赫兹的窄带调频信号（持续时间1500毫秒）测量听觉敏感度。这头海象的水下听力图（50%检测阈值）呈现出典型的哺乳动物U形。最大敏感度（相对于1微帕为67分贝）出现在12千赫兹处。最佳听力范围（相对于最大敏感度相差10分贝）为1至12千赫兹。敏感度在1千赫兹以下逐渐下降，在12千赫兹以上急剧下降。这头海象对2千赫兹的信号表现出特殊的不敏感。它对1.5千赫兹和3千赫兹信号的敏感度要高得多，这表明这是一种窄带现象。海象的听力对低频声音相对敏感，因此该物种可能易受人为噪声的影响。在对四个频率进行的小测试中，信号持续时间为300毫秒时测得的阈值与信号持续时间为1500毫秒时获得的阈值没有显著差异。
