Low‐frequency ambient noise measurements in the South Fiji Basin

Abstract

The effect of wind speed on low‐frequency ambient noise has been measured in an experiment carried out in the South Fiji Basin. This site provides an ideal location for studying sea surface noise, owing to the low density of shipping in the basin. The data were recorded using a towed line array over an 11‐day period in the winter storm season. The local wind speed was measured at the site, with an observed variation between 0–35 kn. The noise measurements in the frequency band 15–250 Hz were strongly correlated with the variations in the local wind speed. The relationship between wind speed v and noise level N is expressed by N = B + 20 n log(v). The constants B and n have been determined by fitting this model to the data at frequencies from 15–250 Hz. At 250 Hz, the values are 22 dB and 1.5 for B and n, respectively. This value for n is higher than the results of similar experiments carried out in the northern hemisphere oceans where the influence of shipping is greater.