Buzzing from heater fan?

Theres a buzzing sound that comes from the blower motor, and it gets louder as I turn up the speed of the fan. So I think something found its way in there. Where is the fan located? Is it easy to get to? Thank you.

The blower motor is under the dash on the passenger side.Remove 4 screws and it drops down with fan cage attached.If something (pine cones,pine needles....etc) gets in from the cowl vent it goes straight to the cage and makes noises like a playing card up against a kids bicycle back wheel's spokes.