Strange noise - 2013 Ford Expedition

after having a strange noise for a second or two when first starting car in morning. found out that when you turn off the a/c unit and the clutch on the compressor is not engaged the noise is gone. then after the car runs for a short time and turn the a/c on there was no noise when the clutch engaged. what is causing this. it only does it when the car sits for more then 9 hours.

Then the noise must be coming from the compressor clutch.