edmontondown 发表于 2013-1-2 23:56 " t% E# f- T$ g0 L- H0 \6 Uyes, may have something fell down on the other end of the hood vent
8 `, I* j* N" T+ `$ }: L! kAt 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.