A radio station in Kansas, KNOR, referred to itself on the air as "K-nor" and in 2008 followed that by a three-tone sound that sounds identical to the three-tone sound that network NBC uses. When NBC learned that KNOR was using the same tone, it sent a cease-and-desist order to KNOR, which KNOR promptly refuted by saying that (1) you can't have a sound as your identifying mark, and (2) even if it can be such an identifier, the frequency of the tones of the KNOR are actually different from that of NBC - with a 1% difference in the frequency of each tone.