DIAGNOSIS This is likely coil whine from the power supply circuitry. It's an electronic buzzing that changes pitch with screen luminance due to varying power load. Not a fan noise, as this model is fanless.
FIX Reduce the electrical load on the monitor's internal power supply. One: Lower the monitor's brightness setting from the OSD (Menu > Picture > Brightness). Start at 80 and decrease until the noise diminishes. Two: Disable dynamic contrast features like Eco Saving or Dynamic Contrast Mode in the OSD (Menu > Picture). These cause rapid power fluctuations that can induce noise.
IF THAT DIDN'T WORK The noise may originate from your specific electrical environment. Plug the monitor into a different wall outlet or a high-quality power strip/surge protector, isolated from other high-draw devices like speakers or desk lamps.
HEADS UP Some level of faint coil whine is common in many LCD monitors and is not typically indicative of imminent failure. However, if the buzz becomes a loud, consistent rattle, contact Samsung support, as this could point to a loose internal component.