Integrating ocean acoustic propagation models and marine mammal auditory models

In responding to concerns about the potential impact of active sonar systems on marine mammals, the US Navy has initiated a research and development program to study the effects of sound on the marine environment (EMSE). As part of the ESME effort, the Naval Research Laboratory is developing a workbench for integrating the diverse software modules under development by other ESME researchers. This workbench models the complete sound propagation path: from the source, through the medium, and to the biosensor system. It allows researchers to explore different scenarios for the interaction between sonar, the marine environment, and marine mammals. There are several issues in building such a workbench. First, the Temporary Threshold Shift (TTS) data for marine mammals are very limited. Both behavioral and physiological models for estimating the TTS for marine mammals as a function of auditory exposure are still in their early stages of development. Second, developing an ocean acoustic propagation model that can produce accurate sound field estimations in shallow water environments is still a challenge. Third, collecting accurate oceanographic data directly such as sound speed profiles, sea floor properties, and bathymetric data is very expensive. The accuracy of oceanographic data directly affects the outcome of an ocean acoustics propagation model. As more and more experimental data are collected, the TTS estimation models for marine mammal auditory systems and the ocean acoustic propagation models will both improve. Furthermore, the Navy has an ongoing effort to collect more accurate oceanographic data. To build a software system that can incorporate software components subject to modification, the components should be modular. Modular components may be easily replaced by improved components provided that the interfaces are clearly defined and stable. This paper describes the current state of this software workbench development effort and discusses the issues involved in integrating different software models developed independently for modeling different phenomena.