Hi, I just moved into an apartment that has steam heat. One of the radiators whistles like a tea kettle a lot, and another just started making awful banging noises, like it had when the boiler wasn't turned on yet. The other two radiators in my place work fine, only mild hissing noises that I can sleep through fine. On the sides of the radiators there is a metal cylinder with a knob on top that can turn from open to close, with numbers such as 1/2 in between. I've never had steam heat before, and I'm a female living alone. Can someone please tell me if this is normal or how to stop the noises so I can get some sleep? Thank you!