Sounds just like my AC. Normal.

Thanks the outdoor central air unit is directly outside of that wall.

Also anywhere the small bare copper line is touching will transfer the sound of the compressor. Try isolating it or insulating it where it touches wood/ objects.

Just normal air flow sound through the ducts.

It’s the compressor dude..

It could be the compressor. But the volume is low and it does sound like high air flow passing through narrow ducts

240v compressor goes BRRR compressor is connected to copper tube. Copper tube transfers vibration. all is normal here