Humming noise on your sound is not due to your speaker but it is come from the amplifier. I've encountered a lot of this problem that is caused by the electrolytic capacitor. If you are a technician first locate for a dry joints on the board and then resolder it using your soldering iron and a high quality soldering lead. Resolder not only the capacitor but also around the output I.C.
If nothing happen then it is coming from your output I.C. sometimes it was leaky/shorted which produces a humming noise but first do the the above mentioned instructions before isolating the defective output i.c.