Marine mammal noise exposure criteria: initial scientific recommendations (2007)

A group of experts in acoustic research from behavioral, physiological, and physical disciplines was convened over a several year period. The purpose of this panel was to review the expanding literature on marine mammal hearing and on physiological and behavioral responses to anthropogenic sound, and to propose exposure criteria for certain effects. The group employed all available relevant data to predict noise exposure levels above which adverse effects on various groups of marine mammals are expected. Recent advances in these fields and the pressing need for a science-based paradigm to assess the effects of sound exposure were the primary motivations for this effort. Two categories of effects were considered: (1) injury and (2) behavioral disturbance. The proposed criteria for the onset of these effects were further segregated according to the functional hearing capabilities of different marine mammal groups, and according to the different categories and metrics of typical anthropogenic sounds in the ocean. The group achieved many of its objectives but acknowledges certain limitations in the proposed criteria because of scarcity or complete absence of information about some key topics. A major component of these recommendations is a call for specific research on critical topics to reduce uncertainty and improve future exposure criteria for marine mammals. This publication marks the culmination of a long and challenging initial effort, but it also initiates a necessary, iterative process to apply and refine noise exposure criteria for different species of marine mammals.