New noise using 3.5mm headphone jack on 2021 M1 24-inch iMac

I have been using the same powered Genelec speakers connected via the 3.5mm headphone jack since purchasing this iMac in 2021 (and a previous iMac ) with zero noise. There is now a high-pitched noise coming through the speakers, even when no audio is playing and the volume is turned down or muted. It does not sound like a ground loop/hum.

I have cleaned the 3.5mm jack a couple of times. I recently updated to Tahoe 26.0.1 thinking it was an OS issue. There is no noise when using Sony headphones using the 3.5mm plug, or with my bluetooth airpod Pro’s. When using the same 3.5mm cord plugged in to my Genelec’s with my iPhone, there is no noise. Nothing has changed (to my knowledge) to cause the sound except adding a new charging station, but unplugging it from the iMac and moving it off the desk does not solve the issue. There are also no new electronic devices in the room.

My only guess is that the internal 3.5mm jack on the iMac has lost a connection, but why would headphones still work perfectly with no noise?

Any ideas? Thank you