Sounds like the motor bearing may be going. May even have some dirt/debris in the fan housing. Should be an easy DIY fix to replace the motor or inspect the fan if you are capable. The power cable will terminate near the blower motor. Kill power to the unit before inspecting it.

Good luck.

Sometimes a piece of paper will get in a fan and cause noise, but usually it's a failing blower bearing that would require that the fan be replaced.

Gas fireplace fans sometimes can be relatively easy to get to, but more often are a difficult pain in the neck, fairly often requiring piping or other parts to be removed to get access to the fan.

A replacement fan usually must be ordered from the manufacturer to get one that will fit in the limited space----figure $175 for the part.

Look for a gas fireplace repairman to do this work. A fireplace shop may have service available or be able to recommend someone.

Congratulations, this is about the peak of the season for having fireplace repairs done.

It COULD be the bearings in the motor but could also be a lot of dirt collected on the fins of the squirrel cage. Sometimes the dirt throws off the balance and makes a noise similar to a bearing going bad. It's a good idea to inspect this every couple of years and clean the dirt off the fins. They have a curve to them and can be kind of hard to clean in place.