Re: return air supply bangs
It's not uncommon for ducts to make the noise your describing .... usually with forced air heating. As the metal ducting heats it will expand and cooling causes it to contract usually at weak or distorted points.... with the cold air return sounds as though it's trying to collapse in your case.
This does bring up some questions ... is this a forced air heating/cooling system and if so does this noise occur during heating?
Has anything been changed with the air handler prior to when the noise first appeared?
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