Why the Beep?...
• Why the Beep? explains why Mathematica CalcCenter produced a beep.
• Mathematica CalcCenter beeps whenever you try to do something it cannot do or does not understand. Choosing this command explains the problem. No matter how many actions you have performed since the beep, the message only concerns the last time Mathematica CalcCenter beeped, and it also tells you how long ago the beep occurred.
• Keyboard shortcut: h (Windows); h (Macintosh).