Underwater noise as source of information on conditions and dynamics of ocean environments

Abstract

Leonid Brekhovskikh wrote in his book The Ocean and the Human (1987): ‘‘Ocean noise is as important oceanographic parameter as temperature, current, and wind.’’ Brekhovskikh created and headed the Laboratory of Acoustic Methods of Ocean Research in 1956. One of the scientific directions of the Laboratory was investigation of underwater noise both as interference for sound reception and a source of environmental information. Long-term studies on the unique acoustic research vessels created under the initiative of Brekhovskikh resulted in numerous important findings, including ambient noise spectra and envelopes of acoustic fluctuations, depth dependence of noise directivity, and mechanisms of ambient noise generation. Brekhovskikh was always eager to find practical applications of scientific results. Different methods of ensuring noise immunity of hydroacoustic arrays were developed under his supervision. Passive methods of acoustic navigation based on use of natural noise were suggested. Techniques for underwater acoustic monitoring of the ocean based either on ambient noise analysis or reemission of noise from a point away from the receiving system have been developed. The success of the team of scientists headed by Brekhovskikh was determined by the creative atmosphere around him: there was neither competition nor commercial interests. The common goal was knowledge of the ocean.