Variability analysis of low-frequency and very low-frequency ambient ocean noise

Abstract

Much of the information presented was made possible by the presence over the past several years of a collection of deep water hydroacoustic arrays with long-term, high data rate recorders of ocean ambient noise, deployed and maintained under the auspices of the United Nations Comprehensive Nuclear Test Ban Treaty Office (CTBTO). Not only does the long time span of the noise record allow high frequency resolution of annual and multi-year variability, but the high data rate supports as well the analysis of high temporal resolution minute-by-minute variability. The present analysis is directed at acoustic frequencies where the noise level and its variability are governed primarily by natural events : planetary—such as the influence of tides, oceanographic—such as the influence of El Nino, and meteorological—such as the influence of storms and routine weather. The analysis is focused on the fluctuations of a series of narrow band tonals at acoustic frequencies between 0.1 and 10 Hz. Results of the analysis display the time scales of the various processes that drive the fluctuations.