edmontondown 发表于 2013-1-2 23:56 5 ]% g& C4 W9 ?/ R; ^yes, may have something fell down on the other end of the hood vent
; `1 u' z* A/ LAt the other end(outside) of the vent duct, there is usually a metal cover for the opening, it can swing up and down and if it is a windy day, it will be blown swinging, thus making a kind of banging noise.