RANDI II—An ambient noise model that includes coherent hydrophone summation for sonar system performance and signal processing in shallow and deep water

The Research Ambient Noise Directionality II (RANDI II) model is described which predicts noise levels and directionalities in specified environmental/shipping conditions and calculates the response of any arbitrary array of hydrophones to the noise field. The model includes a shallow water option based on normal mode propagation. The array response per ship is calculated by the addition of the complex pressure of individual modes at each hydrophone followed by either coherent or incoherent summation of the modes. Shallow water wind noise is provided by a wave theory model for the correlation matrix between all hydrophones of the array. Modeled results are compared with measured data at three different sites, one in shallow water. The agreement is excellent.