Low frequency sound scattering from a submerged bubble cloud: The Seneca Lake experiment

Abstract

Acoustic backscatter from the sea surface is governed by the roughness of the surface and subsurface microbubble distributions. At low frequencies, scattering results primarily from coherent and/or collective scatter from bubbles entrained by the subsurface vorticity or carried to depth by Langmuir circulation and thermal convection. In 1947, Carstensen and Foldy published seminal work on sound scattering and attenuation from bubble screens (JASA 19, 481-501, 1947) in which they employed an effective medium approximation to model the problem. Drawing insights from this work, W. Carey postulated that resonance scattering from submerged bubble clouds can be described by a Minnaert formula modified to account for the enhanced compressibility of the mixture. In 1990, experiments to test this concept were conducted at the US Navy Sonar Test Facility at Seneca Lake, New York (JASA 92, 2993-2996, 1992). Measurements of frequency-dependent backscatter from a submerged bubble cloud proved consistent with model pre...