edmontondown 发表于 2013-1-2 23:56 . r7 @ V( c9 Y' B
yes, may have something fell down on the other end of the hood vent
/ d6 n4 y& T4 o. \6 r% 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.