HomePod Mini keeps making alert tone every hour

I have 2 HomePod minis setup in stereo sound mode. They keep making and alert tone (almost similar to the stewardess call tone on a plane) every hour. I have no alarms set in the home app, I have reset both multiple times. I even reset to factory settings, it stopped for a few days then started back. I have no idea why they are making this tone. Please help.