I appreciate it but I only have a wood deck and no marks on it. I stand over it outside and the noise is coming from it.If the system is sitting with no power on the pressures have equalized between the high side and low side so no refrigerant is flowing. Even temperature changes throughout the day wouldn't cause enough flow to make any noise.
Ive been doing hvac for close to 15 years now and have never heard a piece of equipment make noise like that. Especially something that isn't energized.
Really sounds like a woodpecker going to town on something to me.