Same here, mine sounds like there's a couple marbles rattling around in squirrel cage fan. Sometimes it's louder than others, but if it makes any of that noise, it bothers me. If there's a fix, I'd love to hear it. I opened mine up about a month ago, and didn't see anything obvious. Fans all rotated nice and clean. I put it back together and it was quiet for about a week. I didn't have the guts to plug it in and turn it on while open on the kitchen counter!
Unit is just under 2 years old, with about 1800 hrs on it, original bulb.