edmontondown 发表于 2013-1-2 23:56 * d- n% a& W0 a; wyes, may have something fell down on the other end of the hood vent
) \) i' b; m$ ~7 y d+ WAt 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.