I removed the thermostat from my rack and put it on a table next to the rack and didn't hear the buzz. But when I put my ear to the rack I hear it on the inside.

I'm not sure how it is connected because I bought it off Craigslist and the part where it is connected is inside the rack and covered with tape. I guess I have to take it apart, which is going to be hard to untape and reach to the back of the adult rack. Sigh...