I had to replace the coupler (some refer to it as "the donut" ) with an aftermarket upgrade. Had the rattling sounds and the upgrade worked and has double the mileage of the stock unit with no noise...yet.
Riviera with the same type blower, just bigger...the next model up. I just removed the nose while it was in the car.
Check with the guys below...they'll have a good idea of what it is especially if you play the sound bite for them. That way you can have some verification of what it may be. Since you've had it for a short while (warranty?), you'd be better off swapping for a new one, if it isn't some other issue.
Magnuson Products Telephone Number 800-648-6436 or 805-642-8833.