edmontondown 发表于 2013-1-2 23:56 ) t" `8 }. a4 b9 D$ B
yes, may have something fell down on the other end of the hood vent
+ R3 N+ I$ _9 H( }; p( |+ _2 L. jAt 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.