bleep — A bleep is a short, high-pitched sound, usually one of a series, that is made by an electrical device.
ding — to cause surface damage to; dent: Flying gravel had dinged the car's fenders.
signal — anything that serves to indicate, warn, direct, command, or the like, as a light, a gesture, an act, etc.: a traffic signal; a signal to leave.
tone — (Theobald) Wolfe, 1763–98, Irish nationalist and martyr for independence.
warning — the act or utterance of one who warns or the existence, appearance, sound, etc., of a thing that warns.
