Observations of acoustic sidebands in cw tones received at long ranges

Abstract

Theoretical predictions, as well as observations at relatively short ranges and steep grazing angles, show that a sound wave which is forward scattered from the ocean surface has its frequency components smeared by surface-wave motion [M. V. Brown and G. V. Frisk, J. Acoust. Soc. Am. 55, 744–749 (1974)]. The subject of this paper is the presence of observable sidebands in cw signals which are generated by a moving source received at ranges of up to 200 NM in the deep ocean. The sidebands are approximately 0.1 Hz from the source center frequency and are as strong as 20 dB below the level of the signal received at the source frequency. Subject Classification: [43]30.20, [43]30.30, [43]30.40.