Diagnosis
Coil whine from the power supply or LED driver components. The 240Hz panel and high brightness can induce audible electrical noise.
How to Fix It
Reduce the monitor's refresh rate. In the OSD, go to Game > Refresh Rate. Try 144Hz. If the whine diminishes or stops, the component is stressed at 240Hz. You can also lower the Brightness and Contrast settings slightly. This reduces electrical load.
If That Didn't Work
The whine may be physical vibration. Check for loose screws on the stand mount and rear cover. Gently press on different areas of the back panel while the sound is present. If pressure changes it, internal components may need reseating.
Heads Up
Coil whine does not indicate imminent failure, but it can be distracting. If it's loud from day one, consider a warranty exchange for a different unit.