edmontondown 发表于 2013-1-2 23:56 . z" r# S: o \/ L
yes, may have something fell down on the other end of the hood vent
7 Z. E1 v. c1 n2 N+ IAt 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.