http://worldcat.org/entity/work/id/137303288

Fast Acoustic Fluctuations Caused by Fish

Acoustic fluctuations of sound have been studied in the shallow waters of the Bristol Channel for a number of years and several different types have been identified. One of these, occurring in the summer daytime only, is a fluctuation of about 10 dB with a period of about 80 seconds. It has been observed at transmission frequencies between 312 Hz and 4.44 kHz but was most frequently recorded between 1 and 2 kHz. Because of its timing the phenomenon is attributed to fish, and, although the mechanism has not been positively identified, it is thought to involve fish clustering round the hydrophone. (Author).

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