HomePod Mini plays random music unasked

I have two HomePod Minis that randomly start playing music that's not stored on my system; Apple Music is not playing and I don't have a subscription anyway; there's no browser tab open playing music and no music-playing application sounding off. Plus, the HomePods have lousy taste. The two beasts aren't paired, and are in different rooms. Neither of them are more than a few weeks old. I haven't found any clues in the minimal documentation that came with them, or online.

Why do they do this? Where's the music coming from? I need to solve this quickly otherwise they're going back to Apple. I'm disabled and it's just too difficult for me to have to drop what I'm doing and attend to something that's started screeching at me unasked, and in a foreign language.

TIA for any help.