Effect of waveform distortion on sonic boom noise penetration into a flat ocean

Abstract

The penetrating underwater sound field due to an N-shaped sonic boom incident on a flat ocean surface is well described by existing theory. However, in realistic situations, most of the waves that hit the surface are not perfect N waves but are distorted by such processes as atmospheric turbulence. In the present research, N waves are created that contain the same amount of energy as experimentally measured sonic booms produced by aircraft in the U.S. Air Force. Each signature is input to an algorithm recently presented by Sparrow and Ferguson [AIAA Paper 97-0486 (1997)] to calculate the respective underwater sound fields. By comparing the underwater wave shapes and plots of peak pressure with respect to depth, initial results of the effect of waveform distortion on sonic boom noise penetration into a flat ocean are determined. Preliminary figures show that waveform distortions at the surface cause a slightly greater penetration depth underwater. However, the magnitude of the effect is dependent on the incident sonic boom. [Work supported by Armstrong Laboratory, Air Force Materiel Command, USAF, under Grant No. F41624-96-1-0003.]