edmontondown 发表于 2013-1-2 23:56 ( @2 B& d2 v# I% Ayes, may have something fell down on the other end of the hood vent
8 q3 O; y( m i: t2 v: D- 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.