The commercial era of vessel underwater radiated noise: past, present, and future

Today Underwater Radiated Noise (or URN) is not just about keeping submarines and combatant surface vessels undetectable.  Since the mid 1990’s, vessel URN moved into the public domain for many purposes.  Approaching 30 years as an open topic, much has been learned, many new standards have been issued, and many more are being developed.  As an example, the standard for general acoustic terms, ANSI S1.1 was first published in 1960 with roots back to 1942.  Whereas the standard for general underwater acoustic terms, ISO-18405 was just published in 2017, as much as 75 years later.  Methodologies for measurement of URN have been codified by ANSI, ISO, and ship classification societies.  Europe has written directives for URN limits; Canada is in the process of similar limits and U.S. environmentalists would like to follow.  The International Maritime Organization (IMO, a UN subsidiary) has significant guidelines on vessel URN.  This paper will highlight where and when URN became commercially relevant.  The current metrics, methods, and other guidelines for measurement of ship source sound levels will be addressed.  Finally, what will the future bring for shipboard URN limitations.