edmontondown 发表于 2013-1-2 23:56 ) Y6 J p+ m5 N" `5 [% t( ?yes, may have something fell down on the other end of the hood vent
3 K7 g% u, V$ v% @* b6 hAt 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.