Scientists, whose life is basically spent telling people what they already knew, have confirmed: Whining is the most annoying sound, ever.
Study subjects were asked to do simple math problems while various noises were playing—a crying infant, a table saw, and whining, among others—and found that whining not only slowed down the participants but made their work worse. (The pre-recorded whining was in a different language than that of the subject, so it's not just that American kids are the best/worst at whining—though I'm sure they are.)
Study author Rosmarie Sokol Chang surmises that whining (or our response to it) could be an evolutionary adaptation developed to protect infants. Which, well, we're on board with, because we like the idea of whiny little pre-human babies.