Measuring the source level of wind-generated ambient noise in the ocean

Measurements of the source level of wind-generated ambient noise in the ocean at low frequencies (10-340 Hz) are presented in this paper. The data were obtained using a vertical line array of hydrophones deployed in the deep water sound channel at various sites in the Northeast Pacific Ocean. The array response was steered vertically upward to measure the locally generated sea-surface noise and eliminate the effect of distant shipping noise. The beamforming was carried out with a frequency-domain beamforming algorithm using a spatial Kaiser-Bessel window function to reduce side-lobe levels in the beam pattern. The beam power levels obtained were referenced to a source level at the sea surface using a simple propagation model. An analysis of the relation between the measured surface source levels and measured wind speed data suggest that the noise level is dependent on local wind speed and is influenced by the presence of breaking waves in the ocean. The source levels are compared with measurements reported in the literature.