If you're running Microsoft Windows you can disable the Internal speaker or PC speaker by following the below steps.
- Open Device Manager
- In Device Manager click View and click "Show hidden devices"
- This should make "Non-Plug and Play Drivers" visible in Device Manager.
- Expand Non-Plug and Play Drivers by clicking the plus and double-click Beep.
- Within the "Beep properties" window click the Driver tab.
- Under the driver tab if you wish to temporarily disable this device click the Stop button. If you wish to permanently disable this device under the Startup Type select Disabled.