Underwater sound arrival angle estimation by multiple cross-correlation measurements

A method is described for making in situ measurements of the arrival angles of underwater explosion sounds. The cross-correlation versus time delay of signals from three or more pairs of hydrophones of varied spacings are measured. Each function contains maxima at delays controlled by the vertical and azimuthal angles and contaminating maxima related to the bubble pulse period and the spectral content of the signal. The contaminating maxima are reduced by converting the time delays to angles and averaging the correlations. Usable estimates of the vertical arrival angles are obtained when the azimuthal angles are known and vice versa.