It's in the dictionary as a short, high-pitched sound used to replace an expletive in a broadcast
... To edit out inappropriate spoken language in a broadcast 
by replacing... [DOC] [TLE] BROADCAST GLOSSARY - QSL.net [PAR] The Medialink Broadcasting Glossary was prepared by and used with ... New 
World Dictionary of Media and Communications" -- a 678-page book with 35,000 
... the sound waves or audio signals of a radio station) by variation of its 
amplitude, ..... bleed-through: The bleeding through of the high-pitched whine of 
time code... [DOC] [TLE] Expletive | Define Expletive at Dictionary.com [PAR] Expletive definition, an interjectory word or expression, frequently profane; an 
exclamatory oath.