Measuring the vertical directional spectra caused by sea surface sound

Abstract

The objective of the measurements discussed here is the development of a database of directional spectra obtained in an acoustically isolated area (Tongue of the Ocean, the Bahamas) where the acoustic ambient is principally controlled by the local (observable) sea surface conditions. The purpose of the database is the identification of a model of the space‐time statistics of sea surface sound. A wideband (40‐ to 4000‐Hz) vertical acoustic linear antenna system was used. Data logging took place in a remote autonomously operating subsurface buoy system. Recording restrictions limited each of the seven octavely nested apertures of the sensor system to four wavelengths. However, quite adequate spatial resolution of the directional spectral estimates was obtained using a physically based parametric model of the random process. The results of the initial 2‐month deployment (wind speed range of 2–16 m/s) are discussed here. The measured directional spectra are displayed as a function of frequency, elevation angle, and surface friction velocity. The sea surface sound source structure is discussed.