Fun idea and also I didn't know that websites could get access to my accelerometer data. However for me the sample frequency is 50 Hz which is way too low to measure even the lowest string pitch (E2, about 82 Hz).

If you know you have a single frequency close to an actual frequency of interest, you can use the fact you know you're in an aliased band to get a precise frequency estimate.

Presumably there is an antialiasing low pass filter somewhere before JS gets to the data. I have a similar sample rate and it certainly didn't work at all for me.

I mean yeah, that's cool as a fun project. And I've also heard about a project that used accelerometers as microphones for surveillance. And while it's doable, even the cheapest crappiest mic would do a much better job at recording sounds for whatever is your goal.

> even the cheapest crappiest mic would do a much better job at recording sounds

And if you don't even have that, use a speaker/headphone as the microphone, probably also better results.

guitar detuner that uses accelerometer instead of microphone, it doesn't really work, but amazing to see how sensitive they are.

It also shows that it can leak all kinds of other information.

…which is why both Android & iOS put high-frequency access to the accelerometer behind an additional permission AFAIR.

Anyone got a handle on the algorithm required to do this? I've got a pocketable accelerometer-enabled device I'd like to try to implement this on..

Don't have a handle on it, unfortunately. But the algorithm is in here: https://github.com/tautme/phone-sensors/blob/main/guitar-tun.... Esp. lines 221–257 and 373–417.

Ah, that does look like something I can work with - thanks for the legwork, I will check it out and see if its worthwhile converting to C/C++ for my device ..