edmontondown 发表于 2013-1-2 23:56 $ Q1 f* ?% b7 w4 }4 g1 U- fyes, may have something fell down on the other end of the hood vent
1 y) O) E$ o6 p) z- x) a: s6 BAt 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.