At first I thought it was my chair, but of course not. The sound does not happin all the time and when it does it has a "ting" sound like a blade just barely touching a piece of "heating coil" The "ting" COULD come from a multitude of places such as expansion/contraction in the monitor or box or even the noise of a head HITTING a disk in your hard drive (in the good old days his was called a head crash - a major disaster)

Can you be more specific as to where the "ting" thing comes from?Thanks Dusty,
  I removed a wood box that raised the PC up closer to HAND reach. After that I have not heard the tinging. the move would of created more cool air FLOW so i THINK you were on to something with the heat expansion, the intel active monitor was going off way to often. If the problem continues I;m going to set it on the desk top and stair.
Thanks for the reply
It's really nice to have a site like this
MichaelInspect all your fans to be certain they are running properly. Fans that fail can result in serious damage to computer components that are prone to overheating.