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 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
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.
Idk though when I read it, it seems like it's literally an antenna attached to a can "resonator" is that electronics? It is I guess since it can carry an RF wave? Electronics I think of a chip or circuitry. I get it has to be some form of a circuit to work even as a monopole.
The article says it though: "...hung in his office behind his desk, and which contained an electronic device"
I think if you saw it on a bench hooked up to wires, it would be intuitive that it was a circuit. It's equivalent, but instead of being coupled via wires it's coupled via RF. I think it feels like there's no return path and that the circuit is open, but it's a real circuit with complicated/uncommon coupling to the power source.
A resonator is both a component in the circuit (the case is a cavity resonator) and the type of circuit this is. When illuminated (or hooked up to a power supply on the bench), it produces a sine wave, and holding all else equal the frequency is a function of the capacitance of our membrane capacitor. That membrane is flapping about due to sound, changing the distance between the plates of our capacitor and thus it's capacitance. So this shifts the frequency we're resonating at and encodes the audio into our output signal (frequency modulation).
So it's very similar to a standard LC resonator circuit you might make on a breadboard.
I'll leave you with another story of clever KGB sabotage. The KGB controlled facilities used to construct the US embassy in Moscow in 1979. They were able to extensively bug the building. They were also able to mix thousands of diodes into the concrete. This defeated NLJD (https://en.wikipedia.org/wiki/Nonlinear_junction_detector) based bug detection because they detected the diodes in every direction.
There is something better. The little sensor that maintains the distance between the spinning platter and the armature is sensitive enough to be a reasonable microphone. But it is inside a heavy metal box (the HDD) so you do need to shout at it.
>> They tapped into the feedback system that helps control the position of the read head above the magnetic disk. When the head is buffeted by sound waves, the vibrations are reflected in the voltage signal produced by the drive’s position sensors. By reading this signal, Fu and his colleagues were able to make high-quality recordings of people speaking near the drive.
The NSA could turn on your flip phones mic thirty years ago without you knowing, I don’t think they needed to do all that fancy stuff with hard drives. That’s just research that they funded to cover up the fact that they owned every computing device on the planet for a while.
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.
Wouldn't you need to rewire the headphones? Headphones use a 3-pin TRS whereas a 4-pin TRRS plug is used when you add a microphone. Regardless if the 4-pin is CTIA or OMTP, it's generally only going to get shorted to ground if a 3-pin TRS plug is plugged into a 4-pin TRRS socket, or if a 4-pin TRRS plug is plugged into a 3-pin TRS socket.
This is basic physics controlling the effect here, not electrical routing. Speakers are microphones by their very design. To make them work as a microphone, you merely speak into them with them plugged into an input jack that provides at minimum a line level electrical signal to be modified by wiggling the speaker cone/diaphragm back and forth.
I am crap with physics but was going to say I think the last 50+ years of speaker development has been about making them less a microphone than they inherently are.
Dynamic loudspeakers and dynamic microphones are the same thing. They always have been the same.
They've got the knobs for the design variables turned in different directions, but they're still the same.
They even have the same frequency response whether they're being used as speakers or microphones at the moment.
Which brings up a valid way to measure the response of a microphone's design:
Use two of them. One as a speaker, and the other as a microphone. Play measurement-sounds out of one, and record the results on the other. Plot it out.
The deviations are magnified, but eliminating that magnification is just a math problem -- not an instrumentation problem. :)
They transmit sound. Anything able to detect the vibrations make it a microphone. Not sure how a speaker gets around that because it’s job is to vibrate.
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.
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.
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.
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.
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.
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.
The code mentions "autocorrelation" method: this is a method where you multiply the signal with delayed version of itself: result = sum(x[i] * x[i - delay] for i in some range). You vary the "delay" and pick the value that maximizes the result. This is based on the idea, that the sequential periods of the signal should be similar to each other.
Not a very good method, prone to octave errors (showing pitch one octave lower than the correct one). Furthermore, the "delay" is an integer which limits the precision, so you need to use some form of interpolation. Also it doesn't allow to recognize multiple notes sounding together. Also, slow.
You can read the paper on the "YIN" pitch estimation algorithm which describes the method in details.
I think FFT-based methods are more reliable. I did little experimentation and when measuring a pure sine wave, the frequency can be determined with high precision (tenths-hundredths of a Herz). Not so good in presence of a noise or multiple instruments - I tried to use descending from the hill optimization to figure out the pitch of each harmonic, but it didn't work out.
I implemented the McLeod NSDF pitch method, which normalizes the autocorrelation to get a pretty reliable estimate with fewer octave jumps. For precise tuning I used phase tracking between successive single-bin DFTs tuned to the target frequency.
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 ..
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.
For me it's hard because of tempered tuning, so each string should be slightly out of tune for everything to sound good. If I tuned by ear, I could get two open strings to match, but all the fretted notes and chords wouldn't sound good. On my ukulele I even tune one string down on purpose to make the fretted note sound better. And then there is the inharmonicity of overtones, and some strings have more noticeable overtones that influence how the pitch is perceived.
A good chunk of us are in tune (pun intended) with our instruments to the point that we can simply feel the vibrations and know where we are with regards to tuning.
That sounds like a very useful skill for a working player. But it seems to come with a couple of significant conditions.
I can believe this is possible. But I don't think this is a reasonable thing as a baseline expectation for a player with 6 weeks of experience, which was the original comment in this thread.
I don't know the details, but I imagine you're feeling beats transmitted through the neck or something. But if that is the case (an assumption) it still requires you to have at least one known-good string, unless you're playing solo.
So, for these circumstances, and others, a pedal-based or clip-on headstock tuner seem like they still have plenty of practical application.
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.
When the right defender is near the center I'm reading ~24.74Hz, so slightly above G.
Unless it didn't function like a string at all, then the harmonics would be all wrong.
2011 https://www.researchgate.net/publication/221609349_spiPhone_...
Tangentially, I didn't know this (from Wikipedia):
> The Thing was designed by Soviet Russian inventor Leon Theremin, best known for his invention of the theremin, an electronic musical instrument.
Idk though when I read it, it seems like it's literally an antenna attached to a can "resonator" is that electronics? It is I guess since it can carry an RF wave? Electronics I think of a chip or circuitry. I get it has to be some form of a circuit to work even as a monopole.
The article says it though: "...hung in his office behind his desk, and which contained an electronic device"
A resonator is both a component in the circuit (the case is a cavity resonator) and the type of circuit this is. When illuminated (or hooked up to a power supply on the bench), it produces a sine wave, and holding all else equal the frequency is a function of the capacitance of our membrane capacitor. That membrane is flapping about due to sound, changing the distance between the plates of our capacitor and thus it's capacitance. So this shifts the frequency we're resonating at and encodes the audio into our output signal (frequency modulation).
So it's very similar to a standard LC resonator circuit you might make on a breadboard.
I'll leave you with another story of clever KGB sabotage. The KGB controlled facilities used to construct the US embassy in Moscow in 1979. They were able to extensively bug the building. They were also able to mix thousands of diodes into the concrete. This defeated NLJD (https://en.wikipedia.org/wiki/Nonlinear_junction_detector) based bug detection because they detected the diodes in every direction.
https://physics.aps.org/articles/v12/24
>> They tapped into the feedback system that helps control the position of the read head above the magnetic disk. When the head is buffeted by sound waves, the vibrations are reflected in the voltage signal produced by the drive’s position sensors. By reading this signal, Fu and his colleagues were able to make high-quality recordings of people speaking near the drive.
Diagram: https://i.sstatic.net/8rSD2.jpg
This is basic physics controlling the effect here, not electrical routing. Speakers are microphones by their very design. To make them work as a microphone, you merely speak into them with them plugged into an input jack that provides at minimum a line level electrical signal to be modified by wiggling the speaker cone/diaphragm back and forth.
Dynamic loudspeakers and dynamic microphones are the same thing. They always have been the same.
They've got the knobs for the design variables turned in different directions, but they're still the same.
They even have the same frequency response whether they're being used as speakers or microphones at the moment.
Which brings up a valid way to measure the response of a microphone's design:
Use two of them. One as a speaker, and the other as a microphone. Play measurement-sounds out of one, and record the results on the other. Plot it out.
The deviations are magnified, but eliminating that magnification is just a math problem -- not an instrumentation problem. :)
0) https://www.usenix.org/conference/usenixsecurity14/technical...
1) https://infocondb.org/con/black-hat/black-hat-europe-2014/gy...
Thanks for sharing.
https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampli...
What would that filter look like?
but I don't think it will work well for this case.
My 6-string Kiesel Kyber bass would like a word with you while it sounds 41Hz.
And if you don't even have that, use a speaker/headphone as the microphone, probably also better results.
Not a very good method, prone to octave errors (showing pitch one octave lower than the correct one). Furthermore, the "delay" is an integer which limits the precision, so you need to use some form of interpolation. Also it doesn't allow to recognize multiple notes sounding together. Also, slow.
You can read the paper on the "YIN" pitch estimation algorithm which describes the method in details.
I think FFT-based methods are more reliable. I did little experimentation and when measuring a pure sine wave, the frequency can be determined with high precision (tenths-hundredths of a Herz). Not so good in presence of a noise or multiple instruments - I tried to use descending from the hill optimization to figure out the pitch of each harmonic, but it didn't work out.
https://github.com/dsego/strobe-tuner/
Seriously, this is the very definition of a shallow dismissal.
I haven't touched a tuner in about half a decade.
I can believe this is possible. But I don't think this is a reasonable thing as a baseline expectation for a player with 6 weeks of experience, which was the original comment in this thread.
I don't know the details, but I imagine you're feeling beats transmitted through the neck or something. But if that is the case (an assumption) it still requires you to have at least one known-good string, unless you're playing solo.
So, for these circumstances, and others, a pedal-based or clip-on headstock tuner seem like they still have plenty of practical application.
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.