Our Canon MF 5950 dw is making a humming sound when printing. Does anyone know what might be wrong?

Our Canon MF 5950 dw is making a humming sound when printing, like a repetitive or oscillating hum.  I did not know if there was a fix anyone had. I called customer service.   They recomended I change the cartridge.  I did.  But it still has the repetitive sound.  I have used this machine for over 3 years and it has been a workhorse, but this does not sound good.