Yeah, a faint hum from the power circuitry is pretty common, especially with external power adapters like this one uses.
First, check if the noise is coming from the monitor itself or the external power brick. If it's the brick, try plugging it into a different outlet on a different circuit. Sometimes dirty power or overloaded circuits can make them whine.
If the noise is definitely from the monitor's internals and changes with the brightness or what's on screen, it's likely coil whine from the power supply components. It's annoying, but not usually a sign of imminent failure.
IF THAT DIDN'T WORK: Check the power saving settings. Go to On-Screen Control > General > Smart Energy Saving and turn it off. Sometimes power regulation can cause noise.
HEADS UP: If the noise becomes a loud buzz, crackle, or pop, or if you smell anything burning, disconnect the power immediately. That indicates a component failure.