If its a factory installed beeping sound, remove the door panel and you should be able to see three wires (depending on models) running from the door lock. There should be a black wire that will ground the electrical signal coming from the other wires triggering the warning whenever the door is opened. Cut one wire other than the black one and it should solve the "problem". Before you reinstall the door panel, open and close the door a few times to check if any other stuff in the car is affacted ***Note the "door open" indicator on the cluster...just to be safe.