There was another post on here that is similar to your situation. The other user had a USB DAC next to a wireless mouse dongle and had the same Radio Frequency Interference noise in headphones
A USB extension might not be enough for this situation
If the headphones have a thin cable with not much screening to block noise there might still be some interference picked up just from USB cable
So it may also help to get a headphone extension jack cable for better screening from interference near the jack socket