squawker

noun

1. Something that squawks.
2. A person who complains or protests noisily.

   “The bosses grow weary of the scammers and squawkers and conclude that they're all a big nuisance.”

3. (slang)An informant; a stool pigeon.
4. A loudspeaker used for frequencies intermediate between those of a woofer and a tweeter.
5. (slang)The radio used in police vehicles to keep in contact with headquarters.