Directional wind‐generated noise and its impact on sensor performance

Abstract

It is well known that characterizing the noise field as isotropic may be an unrealistic assumption, particularly when estimating the performance of narrow beam arrays. In this paper, we investigate the effect of an anisotropic noise field on signal‐to‐noise ratio (SNR) as a function of range. A theoretical model that simulates the vertical directionality of wind‐generated ambient noise in the ocean has been developed and is demonstrated for frequencies between 1 and 24 kHz. Noise received by a Chebyshevweighted planar array is evaluated and displayed for a variety of measurement systems and environmental parameters, including beam elevation angle, array depth, water depth, bottom porosity, sound speed profile, and frequency. Additionally, the model demonstrates the sensitivity of the received noise to multipath energy. Using the noise model results, we then predict SNR versus range for both isotropic and anisotropic noise fields, with higher levels consistently seen in the anisotropic field. A comparison of the noise model predictions at selected frequencies with known data bases shows close agreement.