It could be just a noisy fan, if the furnace is a straight shot behind the louvers, it will be noisy, those fans are terrible when it comes to the noise level. I would love to have the 2 speed fan in the low-high fire furnace, many times you would just need the low speed, it would be much better as to the noise level, and comfort level. They start off on high fire and high speed, then switch to low fire and low speed.
The ideal furnace situation is to have the furnace in an offset location, so the air is not a direct shot from the living space. Every 90 degree bend lowers the noise level greatly.