Passive Acoustic Monitoring from Autonomous Platforms

Mark Baumgartner. Woods Hole Oceanographic Institution

Abstract

Passive acoustic monitoring is a vital part of NMFS’ mission to assess and manage
marine mammal stocks, since it provides a persistent and cost effective complement to more traditional monitoring approaches (i.e., shipboard and aerial surveys). Recent advances in automated detection and classification techniques for low-frequency baleen whale calls have made real-time assessment from in-situ acoustic instrumentation feasible. We have developed the capability to remotely detect and report a wide variety of calls produced by several species of baleen whales from autonomous platforms, including Slocum ocean gliders, wave gliders, and moored buoys. The enabling technology for this project is the digital acoustic monitoring (DMON) instrument and the low-frequency detection and classification system (LFDCS), a combined hardware (DMON) and software (LFDCS) system capable of detecting and reporting low-frequency narrowband sounds in real time. The DMON instrument collects, conditions, processes, and records audio from up to three attached hydrophones, and since it is programmable, applications can be developed to detect, classify, and report sounds from the collected audio in real time. The LFDCS is software that detects and describes sounds using pitch tracking, and classifies those sounds using quadratic discriminant function analysis. The combined DMON/LFDCS has been integrated with several autonomous platforms. We propose to (1) demonstrate the utility of real-time passive acoustic monitoring from autonomous platforms, (2) validate the accuracy of our in-situ detection and classification capability when used on a variety of stationary and mobile autonomous platforms, and (3) incorporate this new technology into NMFS whale and fish monitoring efforts. We envision that this project will provide flexible tools for long-term reduction in analytical effort and improved efficiency of existing monitoring technologies (e.g., visual surveys). We anticipate that NOAA will be able to significantly enhance its monitoring efforts using real-time detection information to identify areas of persistent whale occurrence, and to direct airplane or ship based surveys to regions that require additional visual surveillance.