Near-Surface Ambient-Noise Correlation Measurements

Ambient-noise correlation measurements have been made in a deep ocean area with a vertical hydrophone array suspended at a depth of 100 ft. Spatial correlation coefficients were obtained for vertical hydrophone spacings of from 1 to 12.5 ft over the frequency range 100–2000 Hz and for sea states 2 and 4. The measured coefficients are compared to those obtained from theoretical models of ambient noise. The results indicate that below 200 Hz the noise field is mostly horizontal and is attributed to distant sources. Above this frequency, the field can be interpreted as arising from a uniform distribution of directional noise sources at the sea surface.