Popping Noises From Central Air Conditioning: Can They Be Stopped?

Find out why you might hear popping sounds when air conditioning turns on, whether it's cause for worry, and what to do about it. Plus, get advice for quieting noisy pipes.

LESLIE: Richard in Arizona is on the line with a central air-conditioning question. What can we do for you today?

RICHARD: As the heat comes into the duct system, you hear this little popping – I call them “expansion and contraction noises.” When the unit is fully operative and the heat is coming out, it’s relatively quiet until it stops and we go through a period of hearing these tingling and popping noises. So that’s the reason for my call. Is there anything on the market today that might work to quiet down those ducts? The aluminum duct is not wrapped in any form of insulation.

TOM: The answer is probably not but let me give you a suggestion. First of all, there’s two types of duct noises. When the furnace comes on and the blower comes on, right, do you hear any kind of a pop or a bang when that blower comes on?

RICHARD: No.

TOM: OK. Because sometimes when ducts expand, they’ll do what we call “oil-canning” and kind of ping as they sort of flex outward. There is a way to address that. But if that’s not the case, then it sounds to me like – you mentioned it earlier – what you’re hearing is the expansion of the metal and the expansion of the metal where it’s attached to the framing.

So the only thing I can suggest is if you were to replace those fasteners and put a strip of rubber gasket in between – like all across the bottom of the joist, for example – that might quiet that down. But frankly, it’s an awful lot of work. And I know it bugs you a lot but it’s an awful lot of work to try to make it quieter. It really is.

RICHARD: I think so.

TOM: It’s not going to hurt the system in any way. It may just be a little bit annoying but it’s not going to damage it. We get the same kind of complaints from plumbing pipes. Sometimes, when you turn on your hot-water plumbing pipe, it starts to expand and then makes a very similar kind of cricking sound that resonates through the whole pipe. And again, you can quiet the pipes by opening up the wall and moving the pipes and re-securing them and that sort of thing. But it’s generally not worth it because it doesn’t hurt anything. It’s just, really, just an annoyance.

RICHARD: Well, thank you, at least, for your time and your consideration. Obviously, we, as you can hear, have been here for quite a while and we intend to stay here. Matter of fact, we’ll probably just brick up the windows and turn the house into a mausoleum.

TOM: Well, look, you think of it as charm, alright? I don’t think it’s going to cause you a problem and it’s – probably all the houses in that neighborhood probably do the exact same thing. It just happens to be something that really bothers you and I certainly can sympathize with that. But rest assured knowing that it’s not causing any damage, OK?

RICHARD: No, we know that. So, thank you, once again for your time and your information.

TOM: Good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.