edmontondown 发表于 2013-1-2 23:56 & G: X/ t' T8 U
yes, may have something fell down on the other end of the hood vent
7 Y. x& u+ C* @ Z3 I. \At 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.