biased by the animals moving close to the surface in the presence of the sound in order to reduce the received sound pressure level.
This report describes sound origins, trends, effects on marine mammals, and current modeling efforts (Figure 1-4). Chapter 2 provides descriptions of the natural and human sources of ambient noise in the ocean and the possible reasons and evidence for long-term trends in ocean noise. Chapter 3 describes what is known about the impacts of marine noise on mammals, including masking, sensitization, and habituation. Chapter 4 summarizes existing modeling efforts and ocean noise databases, particularly those that integrate the known information about noise with behavioral databases on marine life. Chapter 5 synthesizes findings and recommendations of the committee for future research.