said by Lagamm3 :
(similar to a card in a wheel spoke when riding a bike)
That sound usually means there is something in the blower housing that is rubbing against the blower wheel or stuck in the blower wheel.
I would open up the inducer blower housing and make sure there isn't any debris stuck in there. Also make sure the blower wheel isn't rubbing on any parts of the housing (sometimes the set screw can come loose allowing the wheel to move on the motor shaft).