Philippine Sea observations of acoustic transmission phase and intensity fluctuations and comparisons to path-integral theory

Abstract

From April 2010 to March 2011, low frequency acoustic transmissions were carried out on a 330-km radius pentagonal acoustic array with a sixth transceiver in the middle in the Philippine Sea. Herein, we describe the fluctuation statistics of the signals originating on the six transceivers and recorded on a water column spanning receiver array located slightly off center of the pentagon. The signals analyzed here are interpretable in terms of specific acoustic ray paths clearly separable in time. Acoustic field statistics treated include (1) variances of phase and intensity, (2) vertical coherence and intensity covariance, (3) glinting and fade out rates, and (4) intensity probability density functions. Several of these observables are compared to predictions from Feynman path integral theory assuming the Garrett-Munk internal wave model suitably modified using Philippine Sea oceanographic observations. Data and theory differ by at most a factor of 2 and reveal the wave propagation regimes of unsaturated, and partially saturated.