I have an air duct in my basement. It leads from my furnace (I think?) to the outside world.
However, as you can see from this video, it is "twitching". Every second or so it jerks slightly and makes a noise.
The portion of the duct shown in this video is the end of the duct that terminates outside the house. The rightmost portion of this duct leads to an opening on the exterior wall of the house.
When the furnace switches on, the twitching stops. What's going on? Do I have an alien living in my air-duct?
Update: The end of the duct is not connected to the furnace. It is connected to a clothes dryer. But I still don't know why it is clicking like this.