DIAGNOSIS This is coil whine from the monitor's internal power supply or backlight circuitry. It's a common physical characteristic, not a defect, and is often more noticeable at high refresh rates or specific brightness levels.
FIX Change the refresh rate. Try dropping from 160Hz to 144Hz or 120Hz via your graphics control panel. The change in electrical load often eliminates the noise. Next, adjust the brightness. Set your brightness to either a very low level (20-30%) or a very high level (80-100%). The buzzing often occurs at specific mid-range power loads.
IF THAT DIDN'T WORK Ensure the monitor is plugged directly into a wall outlet, not a power strip or surge protector shared with other high-draw devices like your PC. A clean power source can sometimes reduce electrical noise. If the buzz is only present when G-Sync/FreeSync is enabled, try turning that feature off in the monitor's OSD or your GPU settings.
HEADS UP Coil whine does not affect performance or longevity. If the noise is loud enough to hear over normal room sounds from a distance, you may have a unit with excessive whine and should consider a replacement within the warranty period.