Sonobuoy Acoustic Data Collection during Cetacean Surveys

National Marine Fisheries Service is the largest user of sonobuoys provided by the Navy (Anu Kumar, pers. comm.), where sonobuoys are largely used to study baleen whales during large shipboard cetacean surveys. Data collected during these NMFS cetacean surveys typically fall into one of three categories: (1) opportunistic buoys (in the presence of sighted cetaceans), (2) sonobuoy stations (for larger scale assessment), or (3) real-time tracking of target whale species for focused studies. Despite the potential, numerous complications particular to sonobuoys can negatively affect the accuracy estimation of bearing angles using the DIFAR signal, the quality of the acoustic data, and the interpretation of the data. This report serves to identify methods for data collection that will alleviate many of the problems associated with marine mammal acoustic studies that rely on sonobuoys for acoustic recording and bearing angle estimation. This includes suggested hardware and software methods for data collection, calibration of the hardware system, and protocols and methods for deploying and calibrating the sonobuoys. These hardware and software methods are expected to change over time and recent technological advancements should be considered prior to implementing a research program involving sonobuoys.