New Main Vent Not Making a Sound... Is It Faulty?

I recently fixed (I hope so anyway) a major failure in my heating system. I had to replace two main vents in the basement. One of the main vents does not seem to be making any sounds. No clicks. I stood under the vent during the entire heating cycle and didn't hear a thing. To be fair, it's not too far from the boiler and things are pretty noisy. Is the thing broken? The other main vent is across the room. It makes a very loud clank. It hisses like crazy a few minutes after the boiler stops running. I never paid much attention to the sound of the main vents because they're in the basement. Is this normal?