If this is a new sound, wasn't there previously, with high filtration filters, then the blower motor is probably due to be lubed.
Used to be, blower motors had lube ports but not so much in recent decades so it can be a bit of a process, pulling motor, cleaning squirrel cage while it's out, taking end caps off the motor to replenish the oil reservoirs at both ends.
Some people would just buy a new one, but by the time you had to remove it and install *something* anyway, it's not much more work at that point to lube most motors, as long as the end caps aren't welded on.
If it's not ancient it probably has an inducer motor too, which may also be due to be lubed. I just use 5W-20 motor oil, main thing is relube before they get too loud which is a sign of the bushings/bearings progressively accelerating in wear from needing lubed.
At the same time, lack of lube and wear tends to make noise even without the extra load of the higher impedance filters... just suggesting that replacing the motor probably isn't necessary at this point.