Experimental demonstration of acoustic aberration detection with a vertical hydrophone array

When an object crosses the source-receiver line, a weak acoustic field aberration would be generated. However, it is often overwhelmed by strong direct blast. A lake experiment with a vertical receiver array spanning along water column was designed and conducted, with a 10 kHz pulse. The interested signal was the aberration caused by the forward scattering of a submerged object. The acoustic field aberration caused by the forward scattering of the crossing object can be observed directly, but with only about 3 dB maximum around the direct blast. Hence a principal component analysis on stable portion of beam output was developed for detection with the second principal component of beam output on the vertical receiver array. The beam output waveform at the horizontal direction was processed with the proposed method. The experimental results show that the invariant component of direct blast was reduced and the field aberration caused by the forward scattering of the submerged object can be achieved up to about 10 dB above the background acoustic field.