Diagnosis
This is coil whine, an electronic noise from internal components like the power supply or backlight circuit. It is often related to specific brightness or refresh rate settings.
How to Fix It
Adjust the monitor's brightness. Coil whine on the PD2706U is most common between 20% and 40% brightness. Increase brightness above 50% or decrease below 20% via the OSD (Picture > Brightness). Also, ensure Refresh Rate in the OSD (System > Display) is set to 60Hz, not a lower variable refresh rate.
If That Didn't Work
The noise may be exacerbated by a connected USB-C cable providing high power draw. Try temporarily disconnecting all USB peripherals from the monitor and using a different video input (HDMI) to isolate the source.
Heads Up
Coil whine intensity can vary between units and is not always considered a defect under warranty unless it is exceptionally loud. Document the noise with a video for potential support claims.