Experimental-Theoretical Model of Directional Ambient Ocean Noise

Abstract

A mathematical-experimental model for the prediction of the directional characteristics of deep ocean ambient noise for an arbitrary environment is developed from ray acoustics. The surface disturbance is assumed to be an invariant for all deep-ocean environments and is calculated from directional noise data for several Beaufort wind speeds and frequencies between 500 and 1500 Hz. Utilizing the calculated surface disturbance, dependence of the anisotropic noise on depth (from 150 to 12 000 ft) bottom loss and velocity profile were investigated. Comparison of Beckens averaged data with data predicted from the model agree to within 1° for the location of the null, and to within 1.5 dB for the magnitude at a particular angle. Results indicate the feasibility of predicting the anisotropic noise and show that the shape of the directional noise field is dependent upon receiver depth, the presence of shadow zones, and bottom loss. The predicted change with depth of the noise level as would be measured by an omnidirectional hydrophone was from 0.5 1.5 dB for depths from 150 to 12 000 ft.