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My accelerometer apparently reads at 200Hz, but due to a lack of instrument at the ready I had to "pluck" the handle of the office fußball table.

When the right defender is near the center I'm reading ~24.74Hz, so slightly above G.

This was the direct inspiration for Total Football: to find harmony with the pitch.
heh, a subacoustic G#?
I think the tuner is off by an octave - it has a lot of harmonics and sounded like a G on a bass guitar.
This has some very interesting privacy and security risks. If the tech can do more complex frequency analysis, then couldn't it essentially be used as a microphone for a device that doesn't need permission.
I thought this has been done to capture keystrokes of a keyboard next to the phone already

2011 https://www.researchgate.net/publication/221609349_spiPhone_...

It's a pretty well-known exploit that the CIA is capable of turning a lot of electronics with speakers into microphones. I imagine there is an entire classified backlog of things they can turn into microphones without the target's knowledge.
Tangent but the hidden no-electronics bug "The Thing / Great Seal Bug" really crazy
The CIA…plug a set of regular headphones into a microphone jack, open a recording application and speak into the headphone speaker, you don’t need a 3 letter agency for that physics open secret.
The accelerometers that protect the average hard drive are easily subverted for this purpose.
I mean at this point I'm going to assume that any semiconductor device with more than a few pins has an embedded mems microphone.
it's not (just) the CIA, it's (just) physics
I don't think that's realistic. If you're looking at the acceleration sound waves cause against a phone's accelerometer, that's likely far below the sensitivity of the sensor- phones are too massive relative to the force of sound waves from speaking. F=ma, so the acceleration you're looking at is the force of the soundwave (tiny) divided by the phone's mass (relatively large). The only reason this kind of works is because you're putting the phone on an object that's mechanically vibrating. I suppose it would work in certain situations like putting the phone on top of a large speaker, but you'd never get the resolution to decipher audio from sound waves alone for a phone sitting on a desk or in a pocket
Sounds like you've got a great idea for a proof of concept for DefCon next year...
This is why grapheneos creates 'sensors' as a permission. On android all apps can spy on you this way.
I doubt the sampling rate is anywhere near what you would need to make out dialog in a sound recording. You might be able to tell who is speaking though if you had a voice profile.
The more reliable guitar tuners do something like this. You clip them on the neck, and they detect vibrations in the wood rather than from sound in the air.
Violin/other strings tuners tend to have this mode for orchestra uses with many people next to you also making sounds.
oddly, this is how I learned to tune my guitar. I'm pretty tone deaf, but can feel the difference between the reference string and the string I'm trying to tune through the guitar.
This is fascinating.

Thanks for sharing.

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.
I guess thats sort of like a weird PLL thing? But I'd imagine you'd have to have prior knowledge of which string you're tuning otherwise the analysis is going to alias against every harmonic.
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.
aka a stroboscopic measurement,

but I don't think it will work well for this case.

"the lowest string pitch (E2, about 82 Hz)."

My 6-string Kiesel Kyber bass would like a word with you while it sounds 41Hz.

The very clear and succinct description on the landing page makes me miss the bizarre antisocial charming quirk that people who made things like this used to be stuck with for their copy rather than AI generated language. Our cacophony of experience is quieting.
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.
It really is crazy. Placing my phone on my chest lying down i can clearly see my heartbeat on the graph
it detunes guitars?
The neat bit is that it doesn't necessarily need to sample 82 Hz directly. If the sample rate is known and the target is one of a few guitar strings, the aliased peak can still be useful. The tricky part is probably rejecting the wrong alias once the vibration signal gets messy.
Cool. It worked for E and A but it failed for string 1-4. I was surprised that it worked at all.
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.
Can an accelerometer determine when a car is having issues? Can it do the same for a human user's body?
i remember hearing Porsche was doing some machine learning with vibration analysis to find car trouble. https://www.porsche.digital/en
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.

This sounds neat, but I think I owned a tuner for about 6 weeks before I could do it by ear... EADGBe isn't that hard.
Pack it up folks, nubinetwork has exposed the scam that is the guitar tuner industry. You don’t need a guitar tuner if you have ears; all the guitar techs and musicians who use them have bought into a lie. And obviously since guitar tuners are a waste of time, a tech demo showing that you can use the accelerometer in a commodity handheld device to pick up minute vibrations with sufficient accuracy to detect guitar tuning from a web page is just feeding into the hands of Big Tuner.

Seriously, this is the very definition of a shallow dismissal.

If you have a good external reference point. But it's also pretty easy to have your tuning drift quite a bit away from E standard if you solely rely on the strings. Getting a standard tuning is not the same as getting the standard tuning you want, exactly. This is especially true if you play in standard tunings below E, like C or B, where strings can be looser than the norm.
Pro guitar teacher here with over twenty years of experience teaching the guitar, and close to fourty years of experience playing the guitar. I still struggle with properly tuning my instrument by ear. Nothing wrong with my ears. It's just not easy to do this right.
I can tell if my guitar's significantly out of tune, but no way I'm getting an accurate tune without a tuner.
So what do you do when the lead singer is engaging in some stage banter and you need to tune between songs? IEMs? With what reference pitch?
It's not hard if E is in tune already. :)
i'm like this at home for sure, until i want to play along to something in tune.

i'm also the one at rehearsal literally throwing TU-3s at my bandmates who don't have tuners on their boards for some reason. you have to have a tuner if you play with others. no question.