Review of Underwater Acoustics Research: Noise

The purposes, problems, and progress of radiated noise, self‐noise, and ambient noise research are reviewed. Purposes are related primarily to national defense, but applications to fishery and to the utilization of other natural resources are also noted. Basic problems, most of which were recognized 20 years or more ago, involve ascertainment of properties of the noise, identification of noise sources and mechanisms of noise generation, and the discovery and definition of noise dependencies on environmental factors. Many radiated and self‐noise sources and mechanisms have been identified. Major problems are those of noise measurement, noise reduction, and prevention. In the field of ambient noise, most measurements have been of sound‐pressure level. Some of the noise sources and environmental factors have been identified, and a capability for qualitative and gross prediction has been achieved. Recommended are further investigations of the variation of ambient noise with receiver depth, directionality of the noise field, statistics of both noise level and instantaneous noise values, additional work at frequencies below 10 Hz, and additional geographic coverage, making full use of current knowledge to fashion models for experimental guidance. Challenging problems exist in procedures and instrumentation for noise studies.