Haunted USB sound adapter for Raspberry Pi

I needed a USB sound adapter for a Raspberry Pi device. I found this one on Amazon and also Pimoroni. it works fine. You get stereo audio output and mono microphone input. But the strange thing about it is the eerie glow that you get from the two sockets:

I don’t think the device supports an optical audio connection (which is the only reason I can think of for there being lights in there). However, they do seem to flicker when you plug the device into a Pi.