A method of estimating the influence of ship's noise on ambient noise measurements

Abstract

Ambient noise measurements are often adversely affected by noise from passing ships. Here, a method is presented which allows the estimation of this influence. The method is especially suitable for shallow water applications. It is based on mode interference. The broad-band ship-generated noise is transmitted to the measuring sensor by modes. Because of the interference of these modes, the spectrogram of the noise exhibits interference patterns. Disturbance of ambient noise measurements occurs whenever interference patterns appear in the spectrogram. The degree of the disturbing effect is specified by a mode interference modulation factor which is defined here. In addition, the number of ships and their distance from the measurement sensor can be estimated from the interference patterns. Measurement results are shown which have been evaluated with this method.