The power supply was buzzing.
The repair was super easy and straightforward. It helped that I had taken apart an iMac before and so I already knew the procedure for removing the LCD.
It helps to unscrew the power supply first to make it easier to reach the locking clip underneath for the power distribution cable. if you don't want to buy suction cups, the suction cup that comes with a GPS or other windshield-mounted car accessory works like a charm (but be careful not to stress the glass too much by only using the one cup).