Kastelein Ronald A, van Schie Robbert, Verboom Wim C, de Haan Dick
Sea Mammal Research Company, Julianalaan 46, 3843 CC Harderwijk, The Netherlands.
J Acoust Soc Am. 2005 Sep;118(3 Pt 1):1820-9. doi: 10.1121/1.1992650.
The unmasked underwater hearing sensitivities of an 8-year-old male and a 7-year-old female Steller sea lion were measured in a pool, by using behavioral psychophysics. The animals were trained with positive reinforcement to respond when they detected an acoustic signal and not to respond when they did not. The signals were narrow-band, frequency-modulated stimuli with a duration of 600 ms and center frequencies ranging from 0.5 to 32 kHz for the male and from 4 to 32 kHz for the female. Detection thresholds at each frequency were measured by varying signal amplitude according to the up-down staircase method. The resulting underwater audiogram (50% detection thresholds) for the male Steller sea lion showed the typical mammalian U-shape. His maximum sensitivity (77 dB re: 1 microPa, rms) occurred at 1 kHz. The range of best hearing (10 dB from the maximum sensitivity) was from 1 to 16 kHz (4 octaves). Higher hearing thresholds (indicating poorer sensitivity) were observed below 1 kHz and above 16 kHz. The maximum sensitivity of the female (73 dB re: 1 microPa, rms) occurred at 25 kHz. Higher hearing thresholds (indicating poorer sensitivity) were observed for signals below 16 kHz and above 25 kHz. At frequencies for which both subjects were tested, hearing thresholds of the male were significantly higher than those of the female. The hearing sensitivity differences between the male and female Steller sea lion in this study may be due to individual differences in sensitivity between the subjects or due to sexual dimorphism in hearing.
采用行为心理物理学方法，在水池中测量了一头8岁雄性和一头7岁雌性北海狮未蒙眼时的水下听力敏感度。对这些动物进行正强化训练，使其在检测到声学信号时做出反应，未检测到信号时不做反应。信号为窄带调频刺激，持续时间600毫秒，雄性的中心频率范围为0.5至32千赫，雌性为4至32千赫。根据上下阶梯法改变信号幅度，测量每个频率下的检测阈值。雄性北海狮的水下听力图（50%检测阈值）呈现出典型的哺乳动物U形。其最大敏感度（相对于1微帕均方根值为77分贝）出现在1千赫。最佳听力范围（相对于最大敏感度相差10分贝）为1至16千赫（4个倍频程）。在1千赫以下和16千赫以上观察到较高的听力阈值（表明敏感度较低）。雌性的最大敏感度（相对于1微帕均方根值为73分贝）出现在25千赫。对于16千赫以下和25千赫以上的信号，观察到较高的听力阈值（表明敏感度较低）。在对两个个体都进行测试的频率上，雄性的听力阈值显著高于雌性。本研究中雄性和雌性北海狮听力敏感度的差异可能是由于个体之间敏感度的差异，或者是由于听力上的两性差异。
