My propane furnace blower motor is so loud in my OFF-ROAD POPUP we don't use it much anymore. It is my absolute final PLAN B keeping warm hehe... It will wake me up in the middle of night when it kicks in... Then when we do use it is way TOO MUCH HEAT for our small footprint trailer. Very hard to regulate the heat from it.
I have described the noise like siting in the back roll seats of a MD80 Jet Plane listening to the loud GRRRRRRR Noise of the jet engine which is probably just inches away from your head.
I have never heard a screeching noise coming from my Blower however...
Roy Ken