High-frequency reciprocal transmission experiments in the Delaware Bay: Focus on the direct path

Abstract

Broadband reciprocal transmission experiments were performed in the Delaware Bay during March and September of 1997. Also, direct measurements of current, temperature, and salinity profiles as well as winds and surface wave spectra were conducted during the course of both experiments. The purpose of these experiments was to quantitatively assess the impact of different components of environmental variability (such as tides, wind, etc.) on the stability and coherence of broadband acoustic signals (1–20 kHz) in shallow estuarine environments. In general, the stability and coherence of the received signal will be affected by both surface and volume variabilities, but the impact of volume variability can be most clearly isolated by focusing exclusively on the direct-path component of the received signal. The connection between the stabilty and coherence of the direct-path arrival is studied under different tidal phases, varying wind conditions, and sea states. A preliminary analysis of the impact of volume variability on the direct-path component of the received signal is discussed. Attempts to reproduce these measurements using a high-frequency parabolic equation (PE) model are also shown.