Sea Mammal Research Company, Julianalaan 46, Harderwijk 3843 CC, The Netherlands.
J Acoust Soc Am. 2011 Apr;129(4):2307-15. doi: 10.1121/1.3559679.
Naval sonar systems produce signals which may affect the behavior of harbor porpoises, though their effect may be reduced by ambient noise. To show how natural ambient noise influences the effect of sonar sweeps on porpoises, a porpoise in a pool was exposed to 1-s duration up-sweeps, similar in frequency range (6-7 kHz) to those of existing naval sonar systems. The sweep signals had randomly generated sweep intervals of 3-7 s (duty cycle: 19%). Behavioral parameters during exposure to signals were compared to those during baseline periods. The sessions were conducted under five background noise conditions: the local normal ambient noise and four conditions mimicking the spectra for wind-generated noise at Sea States 2-8. In all conditions, the sweeps caused the porpoise to swim further away from the transducer, surface more often, swim faster, and breathe more forcefully than during the baseline periods. However, the higher the background noise level, the smaller the effects of the sweeps on the surfacing behavior of the porpoise. Therefore, the effects of naval sonar systems on harbor porpoises are determined not only by the received level of the signals and the hearing sensitivity of the animals but also by the background noise.
海军声纳系统产生的信号可能会影响港湾鼠海豚的行为，尽管环境噪声可能会降低这种影响。为了展示自然环境噪声如何影响声纳扫描对海豚的影响，一个水池中的海豚暴露在持续 1 秒、频率范围（6-7kHz）与现有海军声纳系统相似的上扫信号中。扫描信号的扫描间隔随机生成，范围为 3-7 秒（占空比：19%）。在暴露于信号期间的行为参数与基线期间的参数进行了比较。这些会议是在五种背景噪声条件下进行的：当地正常环境噪声和模拟海况 2-8 下风噪声频谱的四种条件。在所有条件下，与基线期相比，扫描使海豚游得更远，浮出水面的次数更多，游得更快，呼吸更用力。然而，背景噪声水平越高，扫描对海豚浮出水面行为的影响就越小。因此，海军声纳系统对港湾鼠海豚的影响不仅取决于信号的接收水平和动物的听力灵敏度，还取决于背景噪声。
