edmontondown 发表于 2013-1-2 23:56 8 c, |% C$ B; t5 x: fyes, may have something fell down on the other end of the hood vent
& U1 O3 D6 {2 X6 _3 ZAt 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.