Early ocean ambient sound monitoring, precursor to soundscapes today, influenced by J. Nystuen

Abstract

In the early 1990s, as the Acoustic Thermometry of Ocean Climate (ATOC) program was starting, simple statistics of ocean ambient sound were unknown. For instance, what fraction of time does the sound level at some frequency exceed a certain value? When the Cold War ended, US Navy SOSUS arrays became available for “dual use” science. At the Applied Physics Laboratory, University of Washington, we began to collect ambient sound data in 1994 from Navy arrays in the Pacific. Initial data spanning 2 years were presented by Curtis et al. [JASA (1999)]. Data and corresponding analyses were separated according to process, i.e., shipping, marine mammals, and wind, as well as for the total. This monitoring effort continued for nearly two decades as reported by Andrew et al. [JASA (2011)], with other collaborators involved (Metzger and Mercer). Throughout, J. Nystuen was always providing guidance and advice in the data analysis and interpretation of the ambient sound data, in fact influencing the first author as graduate students together. We review these early results and connect them to present day understanding and data collection efforts that reflect the status of Ocean Sound as an Essential Ocean Variable of the Global Ocean Observing System.