Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, KY16 8LB, United Kingdom.
Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT, United Kingdom.
Ecol Appl. 2019 Jul;29(5):e01906. doi: 10.1002/eap.1906. Epub 2019 Jun 12.
Concerns exist about the impacts of underwater noise on marine mammals. These include auditory damage, which is a significant risk for marine mammals exposed to impulsive sounds such as explosions, pile-driving, and seismic air guns. Currently, impact assessments use different risk criteria for impulsive and non-impulsive sounds (e.g., ships, drilling). However, as impulsive sounds dissipate through the environment, they potentially lose hazardous features (e.g., sudden onset) and become non-impulsive at some distance from the source. Despite management implications, a lack of data on range-dependent characteristics currently limits their inclusion in impact assessments. We address this using acoustic recordings of seismic air guns and pile-driving to quantify range dependency in impulsive characteristics using four criteria: (1) rise time < 25 ms; (2) quotient of peak pressure and pulse duration > 5,000 Pa/s; (3) duration < 1 s; (4) crest factor > 15 dB. We demonstrate that some characteristics changed markedly within ranges of ~10 km, and that the mean probability of exceeding criteria 1 and 2 was <0.5 at ranges >3.5 km. In contrast, the mean probability of exceeding criteria 3 remained >0.5 up to ~37.0 km, and the mean probability of exceeding criteria 4 remained <0.5 throughout the range. These results suggest that a proportion of the recorded signals should be defined as impulsive based on each of the criteria, and that some of the criteria change markedly as a result of propagation. However, the impulsive nature of a sound is likely to be a complex interaction of all these criteria, and many other unrelated parameters such as duty cycle, recovery periods, and sound levels will also strongly affect the risk of hearing damage. We recommend future auditory damage studies and impact assessments explicitly consider the ranges at which sounds may lose some of their potentially hazardous characteristics.
人们对水下噪声对海洋哺乳动物的影响表示担忧。这些影响包括听觉损伤，对于暴露于爆炸、打桩和地震气枪等脉冲噪声中的海洋哺乳动物来说，这是一个重大风险。目前，影响评估对脉冲噪声和非脉冲噪声（例如船只、钻探）采用不同的风险标准。然而，随着脉冲噪声在环境中消散，它们可能会失去危险特征（例如突发性），并在距离声源一定距离处变为非脉冲噪声。尽管存在管理方面的考虑，但目前缺乏有关距离相关特征的数据，限制了它们在影响评估中的纳入。我们使用地震气枪和打桩的声记录来解决这个问题，使用四个标准来量化脉冲特征的距离依赖性：（1）上升时间<25ms；（2）峰值压力与脉冲持续时间的商>5000Pa/s；（3）持续时间<1s；（4）峰值因子>15dB。我们证明，一些特征在10km 的范围内发生了显著变化，并且在距离>3.5km 处，超过标准 1 和 2 的平均概率<0.5。相比之下，在距离37.0km 以内，超过标准 3 的平均概率仍>0.5，而超过标准 4 的平均概率在整个范围内均<0.5。这些结果表明，根据每个标准，记录信号中的一部分应被定义为脉冲，并且一些标准由于传播而发生显著变化。然而，声音的脉冲性质可能是所有这些标准的复杂相互作用，许多其他不相关的参数，如占空比、恢复周期和声音水平，也将强烈影响听力损伤的风险。我们建议未来的听觉损伤研究和影响评估明确考虑声音可能失去一些潜在危险特征的距离。
