Sound Producing Devices
Regulations do not specifically require vessels less than 12 meters (39.4 ft) in length to carry a whistle, horn or bell; however, the Navigation Rules require sound signals to be produced under certain circumstances. Also, many boats will want to have a horn aboard for negotiating locks and opening bridges. When travelling in fog, proper signals must be used.
Vessels 12 meters (39.4 ft) or more in length are required to carry on board a power whistle or power horn and a bell. The horn or whistle must be capable of a 4 second blast audible for a 1/2 mile for all boats.