No idea, I'm afraid. Does the noise bother you? Do you want them to stop making it? If that's the case, then go upstairs while the noise is happening and ask them nicely to please stop making it. Or only do it earlier in the day, or whatever solution will work for you. "I don't know what you are doing, but that noise I mentioned last week? It's happening now. Could you please figure out what is causing it and stop it? Thank you." Bear in mind that in some apartment buildings, noise travels strangely. What seems to be directly overhead might actually be on one side, or upstairs and over one unit, something like that. But if you go up while the noise is happening, you will be able to hear if it is coming from that unit or not. Or you could just live with it. Once I had upstairs neighbors who apparently dropped a bowling ball on their living room floor every night about 10 pm. Big thud of something falling, followed by a rolling noise. I never did figure out what it was, but it wasn't annoying enough to bother with trying to get it stopped.

We have our first induction cooktop, a Wolf, after cooking exclusively on gas. the cooktop does not make the very annoying noise, but certain pans do. We have only Le Creuset and All Clad, both of which we were told were recommended for induction cooktops. No sound from the Le Creuset, but certain All Clad pans seem to be worse than others. In our experience the frying pans are the worst. Heavier pots and saucepans not as much. And, for whatever reason, one particular non stick pan was the worst of all, so we stopped using it because it was THAT ANNOYING.

cheryl, I ran into this problem a couple of weeks ago with a brand new Liftmaster opener. I ended up replacing the circuit board. I could not pin point what it was, but it was something on the board buzzing. I have not heard back from them. Liftmaster is a very good product. Even the best have a flaw from time to time. Have someone put a board in it and it should be fine. Doorguy

btharmy, the coffee maker draws much less power to keep the coffee warm after it is brewed. Bruce, you were at max load in your testing regime when the hot plate was turned on. As the coil warms up resistance increases and current drops. I bet some of your other breakers buzz when a heavy load is on them. You are just not close enough to hear them talking to you.