Reducing A/c Pipe noise
The condenser is mounted on a plastic footing sitting on the ground. Both the small, high pressure line and the cold low pressure lines are suspended in air and touch the house where they go through the brick siding (foam stuffing in the gaps). The complete unit is fairly new and in good working order.
Your questions prompted me to get my stethoscope and listen. When I put it on the insulated, cold, vapor line the buzz is loud. When on the high pressure, hot line there is not much sound but the contact area is very low (small line, larger flat stethoscope sound board). If I put the stethoscope on the face of a putty knife I hear the sound and it increases as I move the putty knife, in air, closer to both lines. I'm sure the buzz is normal compressor noise, transmitted down the pipes. As I indicated I didn't notice this noise before I took down the wall board in the room. It's now fairly pronounced within a few feet of the pipes. The pipes are not affixed to any part of the structure but mostly run through the stud and joist bay to the evaporator while hanging in air by their own stiffness. The high pressure and low pressure lines are tied together with tie wraps along there length. The structure contact points are 1) at the brick; at the wall; the top plate pass through to the ceiling joist bay; and at the evaporator. The rubber inslulated low pressure line touches the ceiling joist periodically with large single point clamps that do not compromise the insulation, but again it is not clamped tight to the structure.
What surprised me was after spray foaming insulation the sound got worst. I suspect the spray foam, though a good insulator and sealant provided a good sound connection between the pipes and the structure making it worst. I've now dug out the foam in the stud bay and am looking for an alternative. The putty knife experiment shows that where I’ve removed the foam the stud noise (stethoscope against wood) is low but still there. At the bottom of the stud bay where I’ve not yet removed all the foam the buss is much louder in the wood stud bearing out this theory that the foam is transmitting the sound.
Perhaps this noise will again disappear with new wall board, but a big part of this project is to sound deaden the home theater. So I'll feel much more confident if I deal with it before I put up the new wall board.
1) Questions does anyone know if this buss is primarily in the large cold line or the other?
2) Has anyone tried to deal with this buzz before simply installing wall board?
3) Obviously connecting the pipes to the structure with spray foam was bad idea has anyone tried something else?