How To Quiet Noisy Ducts
Answer: Metal ducts make all sorts of noises. In some cases, excessive air flow can cause whistling. Sometimes, pressure differences between the supply and return ducts can move their walls in and out, resulting in a rumbling sound called “oil-canning.” And ductwork can carry the sound of a noisy blower all over the house. But I suspect your problem is caused by hot air rushing into a cold duct, which makes the metal expand....