I found an unexpected downside of induction cooktops. They make an ultrasonic squeal that only my kids can hear and it drives them crazy. I read a while ago that some shop owners were using devices that purposely made the noise to keep kids away. I don’t know if it was specific to that particular model or if there are some that don’t make the noise.

Likely an issue with the hob you have. The squeal will be caused by the high frequency components running the induction ring. Cheap capacitors and inductors will vibrate as the oscillating signal passes through them because the alternating electromagnetic field will cause the windings to gently push and pull on each other.

Problem is solved by either using better components, or better matching the control frequency to the components used so there a no frequency modes that happen to match up with the resonant frequency of components used. Thus eliminating the transfer of electrical energy into mechanical energy.

To expand on the source of noise and possible solutions ...

Regardless of price, multilayer ceramic capacitors are piezoelectric - meaning they physically vibrate. Inductors and transformers are electromagnets powerful enough to noticeably vibrate and move themselves. In fact, if you test them during assembly before taping them, the two halves of the ferrite core will snap together like magnets. Most noise comes instead from the windings, but that gives you an idea of their physical power. The biggest winding in an induction cooktop is the induction coil itself.

The reason you hear them is because they're being used at audio frequencies. Considerate designers choose higher switching frequencies above what humans and household pets can hear. Induction cooktops are kind of a special case where it's tempting to dip into the audible frequencies. Frequency choice alone doesn't eliminate all noise, so there are other mitigations like materials selection and assembly, to name a couple.

Overall, it's largely due to being cheap about the design and manufacturing processes.

Neither of these are solutions available to an actual user of these products though. I worked with these things constantly for years and even the high end commercial line ones make the squeal after a few months of heavy use.

Used to be able to hear it but can't anymore so either they all got better the last few years or I aged out of being able to hear it.

It's an annoying feature in some power electronics, they design the switching frequency to be outside of most peoples' hearing, but not high enough to be completely outside.

I pity the dogs and cats especially!

I suspect the switching frequency is completely outside of any humans hearing range. But there are probably components that have resonant frequencies that are both within human hearing range, and happen to be closely divisible to the switching frequency, and thus will couple to the switching signal and vibrate.

You read that right about the shop owners. One of such device: https://mosquitoloiteringsolutions.com/

There are induction burners made specifically for woks, with the contact surface being curved.

Kenji Lopez-Alt has a good hack for this that uses a torch https://youtu.be/u2MJzEuI0vI?t=481 Not the same, but good enough for me.

For those of us still with gas, Kenji has also recommended removing the the diffuser. Looks absolutely terrifying, no idea if it's safe

https://youtube.com/shorts/JOoaKt4u-gk

lmao holy shit kenji

If only the torch could somehow be placed into the cooking surface.

First time seeing someone cook a fried rice with a butane torch. Is this actually work?

Lopez-Alt recently released a book about wooks [1] where this is mentioned and in my experience it works well for getting the wook-taste and smell.

[1]: http://www.kenjilopezalt.com/books

The winning strategy for serious wok cooking is an outdoor propane burner. Basically no indoor range has the heat output you actually want for the restaurant-style wok cooking.

Also if you are performing true restaurant style wok cooking you doubly want to be outdoors for the offgassing/smoke. Restaurants have hoods that are paired with make-up air systems. That 600CFM (being generous!) "hood" built into your over the range microwave is NOT going to be able to keep up with normal cooking, let alone real wok cooking!

The lack of adequate kitchen ventilation is pretty underrated by most people. Picked up a WYND Halo indoor air quality monitor out of general curiosity and was astonished at just how quickly indoor air can sour when cooking if you don't have adequate ventilation.

I cook a lot more outdoors than I used to now!

Similar issues for blackened food not such a big fashion now.

Ordinary domestic kitchens did not have the ventilation to do it properly.

Maybe you need a different kind of induction stove?

https://www.youtube.com/watch?v=SGBP3sG3a9Y

Free idea to anyone out there: a self-heating electric wok. It shouldn't be too hard to put heating elements spread across the under surface of a wok and make it fully electric.

Electric woks have existed for a long, long time. You can get cheap ones for ~$40USD or go pretty high end and spend >$100USD.

https://www.thespruceeats.com/best-electric-woks-to-buy-4138...

You can get induction wok burners that are shaped for a proper wok (not with a flat bottom).

Pick up a butane camp stove. They're cheap and the size of a dictionary.

not going to have the power for true wok cooking. Burners from Turkey friers are perfect. Also do it outside. True high heat cooking will expel all kinds of smoke and other stuff into the air. Unless you have a high flow hood with a make up air system (similar to what restaurants have - and yes, there are systems made for home/non-commercial use), you do NOT have adequate indoor ventilation to do that kind of cooking indoors.