Did you used gas, or oil for heating? It could be casued by noise of wind. The wind blows air into the pipe from top and then open and close a small door of the pipe near farnace.
check pipes
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• 是屋頂隔層發出的聲音,那裏沒有PIPES. -遠翠- ♀ (0 bytes) () 04/07/2018 postreply 22:47:33