High Pitch Rubbing noise in Engine.. HELP!!

Upon start up when Idling I hear a high pitch rubbing noise from the engine. I usually only hear it when in PARK or Neutral. As soon as I engage into gear it goes away. However , this morning on my way into work I happened to hear it while I was driving. does anyone happen to know what the hell this sound may be an indication of?? Please HELP!
 
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