Whistle from the stands

[Freddy]

I can't find anything in the books, but is not the only means whereby the clock is to be stopped is an official's signal (whistle and/or upraised arm)?
Unfortunate as it was that a whistle sounds from the stands, play must proceed unless halted by the official.
I await others' responses.

By the way, loved you in that movie, Jerry. Though I thought you deserved the woodchipper yourself.