Infrasonic and Low-Frequency Ambient-Noise Measurements Off Newfoundland
Infrasonic and low-frequency ambient-noise signals were measured using three bottom-mounted omnidirectional hydrophones located on the Grand Banks off Newfoundland. Ambient-noise signals from two hydrophones at depths of approximately 600 fm and one at approximately 2300 fm were recorded on magnetic...
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| Format: | Text |
| Language: | English |
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1973
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| Online Access: | http://www.dtic.mil/docs/citations/AD0913868 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0913868 |
| Summary: | Infrasonic and low-frequency ambient-noise signals were measured using three bottom-mounted omnidirectional hydrophones located on the Grand Banks off Newfoundland. Ambient-noise signals from two hydrophones at depths of approximately 600 fm and one at approximately 2300 fm were recorded on magnetic tape continuously for 8 days from 20 to 28 July 1972. The average value of ambient noise in 25 contiguous 1/3-octave bands, at frequencies ranging from 1 to 250 Hz, was measured for consecutive 10-s intervals. Hourly averages were then computed by grouping the 10-s averages into hourly intervals. Autocorrelations of ambient-noise level and wind speed, as well as crosscorrelations of ambient-noise level with wind speed, are presented. The measured ambient-noise spectra in the 4- to 250-Hz range are produced, predominantly, by large ships local to or near the listening area, whereas in the 1- to 4-Hz range a strong wind-speed dependence is observed. It is suspected that the high values of standard deviation (as a function of frequency) were caused by the proximity of the few ships in the area to the hydrophones. The correlation coefficient of wind speed to sea noise is variable and directly dependent on the wind-speed distribution and the amount and location of shipping during the measurement period. |
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