Inverting for surface displacement fields using directly measured point-to-point sensitivity kernels.

Abstract

The effect of surface perturbations on underwater acoustic fields has been directly measured in an ultrasonic tank experiment. High-frequency transducer arrays of 64 elements each are placed 600 mm apart, submerged in ~50 mm of water. A point perturbation is used to displace the surface sequentially in 1-mm steps between the two arrays. At each position a 3.8-MHz signal is transmitted from the source array (round-robin), and the response recorded on the receive-aray, both with and without the presence of the surface probe. The difference between these two measurements yields the point-to-point acoustic sensitivity to that perturbation. These data are explored with respect to inferring the surface structure through both linear full-wave inversions and double-beamforming.