The question: "Why is a kettle loud?" has been asked and answered many times, including on here:
The answer given is that vapour bubbles are being created at the bottom, then collapsing as they rise into the cooler water. This seems plausible.
However, why is it that my induction hob can boil a cup of water faster than my kettle, and do it almost silently?
I used a spectrum analyser app to measure the sound volume in both cases. As you can see, the kettle is considerably louder. In actual fact, most of the noise of the induction hob is actually electrical noise (presumably to do with the alternating magnetic field turning the pan into a speaker).
The pan had a non-stick coating.
Red lines are the peak during the experiment. Green lines are current sound level when screen shot was taken.