It's most likely that the humming noise is being caused by the vibration of fluorescent light bulbs. When the bulbs get hot, they expand and vibrate, which creates a humming noise.
There are a few things you can do to reduce or stop the humming noise:
-Replace the light bulbs with LED light bulbs, which don't vibrate as much and create less noise.
-If you can't replace the light bulbs, try turning off some of the lights in the room to reduce the amount of power being used by the bulbs and therefore reducing their heat output.
-Install a dimmer switch on your lights so that you can control how bright they are and therefore how much heat they produce.