Stop Netbeans Beeping

Well! This might help someone (may be begginer) in getting rid of this annoying Beep. Following this will help you disable Windows Default Beep. So, you won't hear this beep at all even outside netBeans.

1) Go to Control Panel.
2) Click Sound.
3) Click on Sounds in Top Tab Menu.
4) Click on Default Beep from Program Events Sounds List. 
5) Select "None" from the drop down Sounds list.
6) Click Apply.

On Linux, to disable the hardware speaker beep system-wide:

xset b off