Using only ocean ambient noise recordings it is possible to approximate the local time domain Green’s function (TDGF) and extract the time delays associated with different ray path between the elements of a bottom hydrophone array. Comparing the strength of the noise correlation function taken over increasing time windows with residual fluctuations points to an optimum time window to use in the noise correlation function. Through comparison with computer simulations the resulting time series is shown to accurately approximate noise responses in the environment. Analysis of the TDGF gives accurate environmental detail, specifically the critical angle at the water-sediment interface.
Measurements of ambient noise have been used to infer information about the ocean acoustic environment. In recent years the correlation of ambient noise has been shown to give estimates of the travel time of acoustic paths between the sensors recording the noise. A number of issues affect the results of the noise correlation. This paper presents the results of noise correlation of the two horizontally separated arrays of sensors in the 2010 ambient noise experiment. Using the experimental data, the effects on the convergence of the noise correlation are examined with respect to the size and shape of the arrays, the length of time used, and the directionality of the noise field.
This letter demonstrates that the dominant coherent component of low-frequency (1 Hz < f < 20 Hz) ambient noise propagating between hydrophone pairs of the same hydroacoustic station, deployed in the deep sound channel of the Indian Ocean, is directional and mainly originates from Antarctica. However, the amplitude of the peak coherent noise arrivals, obtained using a 4-month-long averaging interval, was relatively low given the small hydrophones spacing hydrophones (<2 km). Hence, extracting similar coherent arrivals between two distinct hydroacoustic stations separated instead by thousands of kilometers for noise-based acoustic thermometry purposes seems unlikely, even using a year-long averaging.
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