97 Wrangler - Loud squeal under hood

I have a 97 Wrangler(Auto) with 65,000 miles on it; I started gettting this loud squeal from under the hood at idle, however when I accelerate it goes away until I am back at idle, but it will also occasionally stop while at idle for a while and then just start back again. I had the serp belt replaced, thinking it was the old belt, but it still continues. Took it to the shop for some other work and they couldn't get it to make the noise while they had it. With the hood up while it is making the noise, I just can't seem to pinpoint it, though it seems like it is coming more from the left side of the engine bay. One of my co-workers suggested a pulley. Any other suggestions would be greatly appreciated. Thanks.