Refurbished t490s - coil hum when using usb-c monitor

I bought a refurbished t490s which was delivered today.

I have a thinkvision external monitor, the M14t. When I connect this via usb-c I can hear a coil hum sound from the laptop. When I just plug a power supply in to that usb-c port it's fine.

I've bought 4 or 5 refurbished thinkpads from the same place over the years, it's an ebay vendor.

I guess I'm just wondering whether this issue is too minor to ask for a replacement. I'm sure some people wouldn't even notice, but I know it will drive me nuts if I used this every day.