The most common thing would be worn tires. It could also be a bad hub bearing. When you turn the car to the right does the humming noise change or go away? If so, the left hub is probably bad. When you turn left if it changes the right hub is probably going out.
it could be your tires on the pavement.
The 2001 Lesabre may have a bad wheel bearing. Check the bearings for all four wheels for a bad bearing.
it does that because it has a generator which makes the engine makes these sounds
Wheel bearing/hub assembly
Possible bad left front wheel bearing. ditto the wheel bearings, get them checked both sides front and rear. This is a serious safety issue.
2001 buick lesabr // when recirculate speed doesnt change only make humming sound rest of heater works fine
Take it to a mecanic.
It is the front hub/bearing assembly; this is a fairly common problem. Buy a new one from the dealer; some aftermarket ones are worse.
I have heard that if you have papers or napkins in the glove compartment box they can get sucked into the air vent which then makes a humming noise that you can hear while driving and as you increase the speed the pitch of the noise gets louder.
Possibly a wheel bearing
One of the main causes for a 1998 Buick LeSabre to die while driving is a problem with the computer. The computer might tell the fuel pump to shut off and stop sending fuel to the motor.
It sounds like the auto hub's are not disengaging. Check the vacuum line on the front axle