A little bit of mechanical noise is normal while in the play mode. It's normally faintly audible in a very quiet room from up to a couple of feet away. Just how loud is this noise you hear and under what conditions are you hearing it? If you are having to put your ear right up to the deck to hear it, there is probably nothing wrong what so ever.
Also, to give us a perfectly clear impression of this noise, it would be best to record it and post a short MP3 of it so that we can tell you if the noise is abnormal or not.