be advantageous to have all data in a single database in order to improve the ability of interested parties to access the data sets and use them in research, for scientific publications, in education, and for management and regulatory purposes. This database could be a distributed network of linked databases, using a standardized series of units of measure. International cooperation in this database development effort, as well as international access to the information, should be encouraged since the marine mammal and ocean noise issue is global.

Recommendation: Existing data on marine noise from anthropogenic sources should be collected, centralized, organized, and analyzed to provide a reference database, to establish the limitations of research to date, and to better understand noise in the ocean.

Each characteristic of noise from anthropogenic sources may differentially impact each species of marine mammals. The complex interactions of sound with marine life are not sufficiently understood to specify which features of the acoustic signal are important for specific impacts. Therefore as many as characteristics as possible should be measured and reported.

Recommendation: Acoustic signal characteristics of anthropogenic sources (such as frequency content, rise time, pressure and particle velocity time series, zero-to-peak and peak-to-peak amplitude, mean squared amplitude, duration, integral of mean squared amplitude over duration, repetition rate) should be fully reported. For transients, publication of actual acoustic pressure time series would be useful. Experiments should be conducted that expose marine mammals to variations in these characteristics in order to determine the physiological and behavioral responses to different characteristics. Particular attention should be paid to the sources that are likely to be the large contributors to ocean noise in particularly significant geographical areas and to sources suspected of having significant impacts on marine life.

Little is known about long-term trends in ocean noise levels. Although evidence is limited concerning long-term trends in ocean noise, and few observations concerning the effects of ocean noise on marine life exist, the current data are sufficient to warrant increased research and attention to trends in ocean noise.

Recommendation: A long-term ocean noise monitoring program over a broad frequency range (1 Hz to 200 kHz) should be initiated. Monitoring and data analysis should include average or steady-state ambient noise as well as identifiable sounds such as seismic surveying sources, sonars, and explosive noise that are not identified in classical ambient noise data sets. Acoustic data collection should be incorporated into global ocean observing systems initiated and under discussion in the United States and elsewhere. A research program should be initiated that develops a predictive



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