edmontondown 发表于 2013-1-2 23:56 . [: M3 e% K% c7 o5 q- |& Fyes, may have something fell down on the other end of the hood vent
! C" G5 \" z% g S/ v3 C g% 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.