My mug of coffee this morning was buzzing with a sound like electric interference, sounded like something straight out of Twin Peaks. Went on for 15 minutes. Normal black coffee, 190F in a ceramic Talavera mug I've used every day for 10 years. What's going on?
Picking it up, moving it around, drinking it caused no change to the noise.
Brewed from freshly ground coffee in an Aeropress with a Prismo filter directly in to the mug.
Video (turn the sound all the way up): https://www.youtube.com/shorts/uvLZRJXTd-8