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 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.
