Acoustic transients research at the Naval Research Laboratory

Abstract

From 1988 to 1992 the Naval Research Laboratory conducted basic research in acoustic transients. This paper will summarize the key results of that research. First, the time‐domain parabolic equation model was developed to predict the effects of the ocean environment on acoustic transient signals. Comparisons between modeled and measured ocean impulse responses will be reviewed and the ability of the model to predict signal feature distortion will be shown for data from an Atlantic, downward refracting, range‐dependent environment. Second, the development of a multi‐sensor deconvolution estimator which makes full use of an array aperture will be discussed. Use of the full array aperture ensures that no part of the impulse response spectrum drops out due to poor illumination. Multi‐sensor deconvolution processors based on this principle have produced stable reconstructions of source time‐series. Data will be shown that illustrate successful multi‐sensor deconvolution that was obtained by a large, vertical, line‐array in a deep Pacific environment for source–receiver separations of 1–2 convergence zones. Third, time‐domain higher‐order correlators were developed for the detection and time‐delay estimation of short‐time/broadband transients. The signal and environmental conditions required for higher‐order processors to outperform conventional cross‐correlators will be shown.