- Alicia Spinnet: "It's just so unfair. I mean, what about Crabbe and that Bludger he hit after the whistle had been blown? Has she banned him?"
- Ginny Weasley: "No. He just got lines. I heard Montague laughing about it at dinner."
- — Alicia complains about Harry, Fred and Georges' Quidditch ban.[src]
A Whistle is an instrument which produces sound from a stream of forced air. It is used by a Quidditch referee to signal the start of a game, fouls, time-outs and ends a game.
There existed a spell to turn a whistle into a pocket-watch.