Tour company Ride the Ducks is suing rival tour company Bay Quackers, alleging that it holds trademark rights to the sound made by tourists using duck call devices, while on amphibious vehicle tours. San Francisco-based Ride the Ducks holds a 'sound mark' on the noise. Very few companies hold sound marks, but some of the more famous include: the NBC chimes and the MGM lion. The company holds US Trademark No. 2,484,276, which protects a mark consisting of 'a quacking noise made by tour guides and tour participants by use of duck call devices throughout various portions of [guided amphibious vehicle] tours.' Reading this makes my think that there is a room full of litigious monks somewhere, just waiting for someone to try clapping with one hand.