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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

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  • Are you absolutely sure the noise was coming from the mug? (can't tell from the video).
    – FuzzyChef
    Nov 30, 2023 at 22:04
  • Yeah, absolutely from the mug. From the middle of the coffee. A friend pointed out that at 00:15 there's a small static discharge on the rim Dec 4, 2023 at 15:21
  • Did you microwave it?
    – FuzzyChef
    Dec 4, 2023 at 16:15
  • Nope. Directly from pressing the coffee. Dec 5, 2023 at 9:32
  • Is this 50/60 Hz? Any electrical devices in the neighbourhood, already buzzing but inaudible, resonating in a coffee-cup-cavity that happens to be just the right size (fluorescent lighting?) Dec 9, 2023 at 10:37

1 Answer 1

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When I've gotten buzzing sounds in the past, they were due to the hot liquid heating up air in the porous material of the cup, which then pushes against surface moisture to fizz. I would guess that the downward Aeropress pressure has finally caused some micro-fractures in your mug.

You can probably test this by starting with the mug dry and cool, and dipping it into hot (115 F) soapy water. Look for tiny bubbles.

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    I reckon that's really close but suspect it's more that the ring of unglazed material on the bottom was damp, and heating the mug by filling it with hot water caused that dampness to evaporate and the vapour to bubble out. You'd need water under the rim to make enough of a seal for bubbling rather than gentle flow
    – Chris H
    Nov 30, 2023 at 14:40
  • Thanks, not bubbles in this case. Also, not from underneath either. Sound continued as I picked it up and turns it around by my ear to try to determine the source. Dec 4, 2023 at 15:23

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