Marine mammal auditory systems: a summary of audiometric and anatomical data and its implications for underwater acoustic impacts

Concomitant with man's increasing use of the oceans is an increase in the ocean's acoustic budget. In the mid 1970's, it was estimated that noise from human related activity was increasing in coastal areas and shipping lanes at 10 dB per decade. Given our ever increasing activity in all seas and at all depths, this figure is not surprising. It may even be too conservative. Anthropogenie noise is an important component of virtually every human endeavor in the oceans, whether it be shipping, transport, exploration, research, military activities, construction, 01' recreation. For some activities, such as military and construction, impulsive and explosive devices are fundamental tools that are intermittent but intense; for others, such as shipping, the instantaneous noise may be less, but sound is inherent in daily operations and is therefore a constant, pervasive by-product. Because these activities span the globe and produce sounds over the entire audible range of most animals, it is reasonable to assume that man-made noise in the oceans can have a significant adverse impact on marine species. Because marine mammals are especially dependent upon hearing and in many cases are endangered, the concern over noise impacts on these animals is particularly acute. Our concern is both logical and appropriate, but it is also, at this time, unproved and the range of concerns is unbounded. For responsible stewardship of our oceans it is imperative that we begin to measure and understand our impacts, and, more important, that we proceed with a balanced and informed view. To that end, this meeting is a significant, positive step.