Woop

The sound made by the materialization of the Death bots of Krikkit, re: Life, the Universe, and Everything, usually described in terms of being pronounced by several thousand people saying "whoop" at once.

Life, the Universe, and Everything is the third book in the increasingly inaccurate Hitchhiker's Guide trilogy by Douglas Adams.

Like a few other things in the Hitch Hiker books, this word was changed for the American releases. Oringinally, and in any British edition of the book, the sound effect is several thousand people simultaneously saying "wop".

This change was understandable but pretty much unnecessary.