Thread: What is this weird sound I hear occasionally in the vent (or maybe the wall)?

Every few hours, I hear a noise either in the vent or the wall that sounds like FFFFFFT (that is the best way to describe it lol).... It only lasts for about a second or two and then it stops. Anyone know what this could be?? BTW - It is freezing cold where I am and we have the heat on a lot. Thanks.

Do you have steam heat with a spitter on it. Part of the water filter on some. Spit every so often off the bottom of it. To remove settled impurities. Like a settling bowl for solids.