Why the Beep brings up an explanation of why the front end produced a beep.
Mathematica beeps whenever you try to do something it cannot do or does not understand. Choosing this command explains the reason for the last beep and tells you how long ago it occurred. The message only refers to the last time Mathematica beeped in the current session.
Keyboard shortcuts: h (Windows); h (Macintosh); h (X).