| Abstrakt: |
Recordings of ambient sea noise from four deep water sites between Australia and New Zealand have been examined for correlation between the narrow-band spectrum level and the observed local wind speed. Significant wind dependence is observed at all frequencies between 37 and 800 Hz. When the results are reprocessed to examine only locally generated noise (horizontally arriving sound from distant sources is rejected by making use of the directional properties of a steerable vertical hydrophone array), it is found that the wind dependence of the observed noise at low frequencies is significantly enhanced. The rate of increase of locally generated noise with wind speed is very similar to published values for Australian waters, except for frequencies below 100 Hz, and much lower than most reported measurements in northern hemisphere waters. By steering upward-looking beams, the levels of sound radiated (per steradian) from the surface, at various wind speeds, were measured. The measurements were adjusted, where necessary, to account for variations in bottom loss at different sites, using measured normal incidence bottom reflection losses. At the higher wind speeds the spectrum of the estimated surface source level appears to be almost flat across the band of frequencies observed, which is a feature of recent published results from other oceans. At lower wind speeds the results rise with decreasing frequency below 100 Hz suggesting the addition of noise from a different source which has not been identified. [ABSTRACT FROM AUTHOR] |
