DIAGNOSIS That's electronic coil whine. It's caused by components (like inductors or capacitors) on the monitor's internal power supply vibrating at a high frequency under electrical load. It's annoying, but not usually a sign of imminent failure.
FIX Unfortunately, there's no true 'fix' short of a component-level repair, which isn't practical. You can try to minimize it. 1) Make sure the monitor's power cable is plugged directly into a wall outlet, not a power strip or surge protector that's sharing load with other noisy devices. 2) Try a different power cable if you have a spare. 3) Sometimes adjusting the brightness or contrast in the OSD can change the electrical load enough to shift or reduce the noise. Try setting Brightness to 80% and Contrast to 70% as a starting point.
IF THAT DIDN'T WORK If the buzzing is extremely loud or changes to a popping/crackling sound, that could indicate a failing component. In that case, and if the monitor is still under warranty, contact Sceptre support. For persistent mild whine, your only real solution is to move the monitor further from your ears or mask the sound with other ambient noise.
HEADS UP This whine is often more noticeable in a quiet room and when the monitor is displaying very dark scenes, as the power regulation circuitry is working differently. It's a common issue across many electronics, not unique to this model.