Has anyone insulated to cut down on furnace noise?

I recorded the squeal on my phone and am using that recording to test different materials for sound dampening ability. Egg crate...not so much. Interesting, my rig is a 2001. I bought it in 2007. And I noticed that the date on the motor that's in there is 2005. So the first motor only lasted 4 years. Then it started squealing 5-6 years after that. These motors sure aren't designed to last very long.