edmontondown 发表于 2013-1-2 23:56 # X- m$ G) K) ^# I+ t, _yes, may have something fell down on the other end of the hood vent
( V9 J6 d2 I. t2 DAt 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.