Yes, this is a known issue (in windowed mode, as well).
You can avoid this by using the arrow keys to move the camera or adding a secondary hotkey for 'Show World Tooltips' (or changing the primary) to use something other than Alt.
Alternately, you can right click the Windows volume control in the task bar, select Sounds, in the Sounds tab select 'Default Beep' under Windows and change it from 'Windows Ding.wav' to '(None)' (assuming you don't mind loosing the beep in Windows globally).
