Spatial and temporal fluctuations of the sound field during shallow water 2006 (SW06) experiment

Abstract

During a multi-institutional shallow water experiment in the summer of 2006 (SW06) a series of source-receiver positions were designated to examine the effects of 3D environmental fluctuations on the propagation of low to mid frequency (0.05–3 kHz) broadband acoustic signals. During each scheduled transmission a ship equipped with an acoustic source and a vertical receiver array was positioned at a fixed coordinate determined by the real-time measured position of an internal wave (IW) regime. The passing IW packet in each one of these events was measured by additional research vessels to assess the oceanographic conditions. At the source-receiver ship, the passing IW was observed and its speed and wavelength was measured from surface features using ship’s radar within 3-NM radius from the leading edge of the IW on approach. Each event was photographed at 30-s intervals. In addition, thermistor array data were collected simultaneously. A total of 57 passing IW events were recorded during 21 days through which broadband acoustic signals were transmitted at different source-receiver angles with respect to the IW front. This paper presents preliminary data processing of the observed data. [Work supported by ONR-321OA and RFBR.]