Background Noise in Underwater Acoustic Listening Systems.

摘要

In the last few years it has been shown that under most circumstances there are two primary sources of ambient noise in the frequency range from 10 to 10,000 Hz. Their relative importance varies from situation to situation, and under some conditions, such as heavy rain or high biological-noise levels, additional sources are important. However, in all cases, the two primary sources must be considered. One of these sources is surface agitation. It is highly wind-dependent, and the noise that it generates arrives at our systems from vertical and nearly-vertical angles. The other source is distant shipping. Shipping noise is not wind-dependent and arrives at listening systems from nearly-horizontal angles. If one neglects nearby shipping, then this noise is characteristically lower in frequency than surface noise and propagates for long distances. The information presented here will relate to knowledge of ambient noise consisting of contributions only from the two primary sources--surface agitation and distant shipping. We shall consider first the reliability with which ambient-noise levels can be predicted and then the important characteristics of the noise itself.