I have been tripping over this for a while. If heat and sound are both essentially vibration, is it possible for certain temperatures to cause audible sounds in substances? Specifically, I am trying to figure out at what temperature wrough iron will vibrate just right... like a bell or something. I heated a cannon ball and it really seemed to be emitting a sound. Would that be an effect of the air temperature being raised, or is it possible that the molecules of metal kinda start ringing?