When my Bryan furnace (310 AAV-JAV) turns on, the fan noise seems too loud at the start and also comes with a "rainy" sound in the background. The fan noise dies down some after the initial burst. All the noise goes away when it is off. We only noticed this kind of loud noise lately.

Thanks for the help!

Check or replace capacator. If this doesn't do the job, you will most likley need a new blower motor

Sounds like the blower wheel is coming apart. If this is the case, replace it before it starts ejecting vanes and damages the unit.