the National Oceanic and Atmospheric Administration, the National Science Foundation, and the U.S. Geological Survey, the National Research Council (NRC) of the National Academies undertook a study to examine the current state of knowledge on ocean noise and its effects on marine mammals. The NRC was asked to

  • evaluate the human and natural contributions to marine ambient noise and describe the long-term trends in ambient noise levels, especially from human activities;

  • outline the research needed to evaluate the impacts of ambient noise from various sources (natural, commercial, naval, and acoustic-based ocean research) on marine mammal species, especially in biologically sensitive areas;

  • review and identify gaps in existing marine noise databases; and

  • recommend research needed to develop a model of ocean noise that incorporates temporal, spatial, and frequency-dependent variables (Box 1).

The committee held three public meetings and received input from underwater acousticians, marine mammalogists, auditory physiologists, and naval oceanographers. The committee reviewed previous NRC reports (NRC, 1994, 2000), current scientific articles, symposium reports, models, and data compiled by the Naval Oceanographic Office.

This report is the third in a series by the NRC examining the potential effects of ocean noise on marine mammals. Although the three reports evolved from very different charges and were generated by separate committees, many similar research needs became evident during each study. The recommendations presented in this report build on, but do not replace, those presented in the earlier efforts (NRC, 1994, 2000). This committee recommends that all three reports be examined in order to better understand the research needs required to mitigate the effects of human-generated ocean noise on the marine ecosystem.


For the purposes of evaluating the potential effects of underwater sound on the marine environment, both ambient noise and noise from identifiable sources must be considered. The term “ambient noise” is used by the underwater acoustics community to refer to the background din emanating from a myriad of unidentified sources. Although the type of noise source may be known, the specific sources are not identified. When examining the possible effects of ocean noise on marine mammals noise from specific sources is also important; therefore, the term “ocean noise” will be used in this report to refer to all types of noise sources.

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