DIAGNOSIS: Yes, that's almost certainly coil whine. It's a high-pitched electronic buzz that comes from the internal power components, especially common when the monitor is outputting a very high refresh rate (like 180Hz) or during high frame rate, dark-colored scenes.
FIX: First, try changing the refresh rate. 1) Press the joystick, go to Game Adjust > Overclock. 2) Turn 'Overclock' to 'Off.' This drops the max refresh rate from 180Hz to 165Hz. See if the buzzing diminishes or stops. The higher the refresh rate, the more likely coil whine is to occur.
IF THAT DIDN'T WORK: The whine might be tied to a specific feature. Go through the Game Adjust menu and try turning off features one by one to see if it stops. Try 'Adaptive-Sync' off. Try 'Black Stabilizer' at 50. Sometimes a specific combination of settings stresses the power circuitry differently and induces the noise.
HEADS UP: Coil whine, while annoying, doesn't indicate a failing monitor or a safety issue. It's a physical vibration of components. If it's very loud and happens at all refresh rates, contact LG support, as it might be excessive enough to warrant a warranty claim.