Your blower motor is going bad. There is a DIY for replacement in the DIY section. It is a very easy repair. The motor is less than $100. What has happened is the motor bearings have gone bad. It is due to a poor design in regards to the orientation of the motor. The motor uses a squirrel cage type fan blade. The motor is oriented vertically, meaning the motor shaft that the fan is mounted on sits straight up in a vertical position. This orientation allows for water, or condensation, to creep down the shaft and into the shaft bearings. Once the water gets in the bearings, they rust and wear out.
The noise you hear is the fan blade rubbing on the motor housing.