I mounted a couple of hand held air-conditioning fans to a back support belt and used some ribbed tubing to duct the air up my collar and under my bucket.
It has made troops so much more comfortable, however, I can't hear anything but the sound of wonderful cool air

http://fav.me/d52rx42
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The second picture has them against a white shirt so you can see what is going on there.
Some updated pics, I painted the Handy Coolers to match my armor and bucket.
http://fav.me/d58v58i
http://fav.me/d58v504
http://fav.me/d58v4vl