Diagnosis
Yeah, this one's common. It's coil whine from the internal power supply or components, and it's often tied to the monitor's refresh rate or brightness level.
How to Fix It
First, go into the OSD under 'Game Setting' and make sure 'Refresh Rate Num' is set to 'On' so you can see the live refresh rate. Then, try changing the refresh rate in Windows display settings. If you're at 60Hz, try switching to 59.94Hz or vice-versa. Sometimes a specific rate makes the components resonate. Also, try adjusting the brightness up or down a few notches; the whine often changes pitch or disappears at certain brightness levels.
If That Didn't Work
The whine can be more pronounced when using HDR or certain high-contrast modes. Go to 'Picture' -> 'Picture Mode' and switch out of 'HDR Effect' or 'Game' modes back to 'Standard' or 'sRGB' to see if it lessens.
Heads Up
This noise is generally harmless and doesn't indicate imminent failure, but it can be annoying in a quiet room. If it's loud from day one, an exchange might be your best bet, as the severity varies unit-to-unit.