I have a pair of desktop speakers that have both a USB input (to an onboard DAC) and an analog input; originally, I had the USB input connected to an iMac and used the analog input to plug into my work laptop. Recently, I swapped the iMac for a Mac Studio and a Studio Display, and figured that I could just unplug the Thunderbolt cable to the display from the computer and plug it into the laptop. I kept using the analog cable, though, because I wanted to keep the speakers directly plugged into the computer rather than the hub on the display, probably due to irrational audiophile-esque superstition that this would make the sound laggy or the highs less chocolaty or whatever. (More seriously, I've heard of DACs having stuttering issues when they're run through hubs, and hey, I had the cable, right.)

And the first time I plugged the analog cable into the same laptop that I'd been using, the only difference being that the Thunderbolt cable was also plugged into it, it was terrible.

Despite the audiophile joke above, I don't mean terrible in some kind of "this cable is making the sound subjectively worse" fashion, I mean terrible in a "when no sound is playing, I can hear grinding electrical noise going BZZZZZbzzzzGRRRFTTTTgrrnkFFFFNK constantly" fashion. The problem was clearly the Thunderbolt cable, even though it wasn't involved in the audio circuit at all. It's like it had turned into its own little RF interference generator. While I only had the one Thunderbolt cable so I couldn't swap it, the interference went through two different analog cables.

(This is not as weird as hearing RF interference over one specific pair of headphones from a headphone amp when nothing was playing but only when I was using a specific USB cable running to the same outboard DAC, which also happened to me years ago.)