Loud buzzing at charger when connecting to usb-c monitor

Hi there, I have had this issue that my charger started buzzing and overhearing randomly a few weeks ago. After getting a new charger and troubleshooting a bit I figured out it is only buzzing when an external monitor is connected via one of the USB-C ports. I am not sure why this is happening since the monitor has its own power source.

The charger is the 96W block with thunderbolt connection and the three prong grounded extension cable. The monitor is also grounded. Both are protected by surge protectors.

Has anyone seen this issue before?