Study of Ambient Noise in the Deep Ocean

Abstract

An understanding of the characteristics and nature of the ambient noise is fundamental to the design of long-range submarine detection systems. During the summer of 1959 a series of deep-ocean ambient noise measurements were made with a 10-element vertical hydrophone array suspended to a depth of 500 fathoms in 2000-fathom water. Measurements were made over the frequency range of 5 to 25 cps. All data were recorded on magnetic tape and returned to the laboratory for analysis. The objectives of the measurements were to determine the spectral nature of the ambient noise and any special properties such as directionality that the ambient noise might have. By use of a magnet drum delay line, the array was steered in a vertical sense about the center of the array. The intensity and frequency spectrum of the beams was recorded. Broadband spectrum analysis was made, and both frequency and power spectrum plots were obtained of the ambient. A considerable amount of biological noise was recorded, and some classification of these signals was made. This paper describes the method and instrumentation used in recording the raw data and a description of the data analysis techniques. The results of the data analysis program are then discussed in detail.