Horizontal directionality estimation considering array tilt and noise field vertical arrival structure

A new approach to undersea ambient noise field horizontal directionality estimation from towed line array data is presented. This new technique includes the effects of the three-dimensional array response and the noise field vertical arrival structure during the estimation process. It is sufficiently general to include the angle of array tilt from the horizontal and does not require noise field stationarity as do most previous methods. The vertical dimension is included in the estimation process through a transformation of the noise field from a spherical coordinate system to a conical coordinate system of the array with an arbitrary tilt angle. The three-dimensional pseudostationary noise field estimate ? (ϑ,φ) which results is then integrated over the vertical (φ) to obtain the horizontal directionality estimate ? (ϑ). The results indicate significant improvement in ? (ϑ) when the array tilt and noise vertical arrival structure are accounted for.