Sometimes the docking sound of a USB connection is played on the PC-Module, without actually connecting a USB.
1. Open the Control panel of your OPS module
2. Go to the 'Hardware and Sounds' menu
3. Click on 'Change system sounds'
4. Select the tab 'Sounds'
5. Select 'Notification' under 'Programme activity log'.
6. Now press 'Sounds' in the same tab and select the option '(no)'.
7. Press 'Apply'