Biological Choruses in the Eastern Indian Ocean.
WEAPONS SYSTEMS RESEARCH LAB ADELAIDE (AUSTRALIA)
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This report is a summary of observations of biological choruses in the eastern Indian Ocean. The data were collected from underwater noise recordings made in the course of sonar performance trials at four sites north-west of Australia, located in intermediate and deep water. Measurements are made for frequencies between 20 Hz and 800 Hz. Chorus noise at 500 Hz consisting of continual drumming sounds, was evident for 10 hours in the evening, with the peak noise level occurring soon after sunset. The noise spectrum level at this peak frequency rose to 72 dB re 1 micro Pa2Hz, approximately 10 dB above the background noise level. Typical spectra and time waveforms for individual noise bursts are presented. The source of the noise is believed to be fish of the family Sciaenidae, commonly known as croakers.
- Biological Oceanography