Model tests to determine propeller-induced hull pressure fluctuations are carried out on a regular basis for many ship types, such as cruise ships, yachts, container vessels and bulk carriers. Such tests focus on onboard noise and vibrations. Underwater radiated noise (URN), however, was traditionally mainly of interest for naval vessels in relation to their signature. Class rules also include noise limits for fishery and seismic research vessels because self noise can influence the operability of such vessels. Recently, noise of other ships types has also received regulatory attention. URN-related class notations have been introduced for cruise vessels and yachts for example. These can be used to show that the URN of such a vessel has been controlled to reduce the impact on marine wildlife. The noise from ships should be sufficiently low to avoid interference with sound used by marine mammals and fish to communicate and navigate. It is likely that in the near future local regulations concerning URN will come into force to protect wildlife in particular sensitive areas. Furthermore the European Union has included URN in methodological standards regarding good environmental status.