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SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit [pdf] (2017)
- deleted 6mo ago[deleted]
- BFV 6mo ago[flagged]
- hecanjog 6mo agoThis shouldn't be downvoted. Transducers being reversible is a neat and non-obvious thing.
- dnnddidiej 6mo agoMotors can be dynamos too
- maqp 6mo agoand many LEDs are weak photo-diodes, i.e. you get weak current when you shine a light to them.
- saagarjha 6mo agoIt's probably downvoted because it sounds somewhat nonorganic.
- 3form 6mo agoEven with the em-dash. New account and other comments seem to be here-and-there. Maybe LLM with some editing after.
- mkl 6mo agoIt's pretty obvious if you did high school physics. I experimented with earphones as microphones as a teenager but couldn't get any meaningful audio data. I think they're being downvoted because their comments all seem to have AI features.
- vidarh 6mo agoI hadn't thought about whether this would still with modern speakers, but this was the common assumption for several older types of speakers and microphones. One of the first "science experiments" my dad showed me was the other direction: Dismantling our telephone and demonstrating that the carbon microphone (yes, I'm old) in the handset would also work as a (really bad) speaker.
- atoav 6mo agoIt is basically the same as turning a motor into a generator.
- deleted 6mo ago[deleted]
- ijk 6mo agoI feel like this is the kind of hack that made early radio tech exciting to play around with. The basic parts are incredibly simple to assemble from scratch, so it feels like magic. Speakers and microphones are the same thing in reverse. And so on.
- Rekindle8090 6mo agoThis user is an LLM.
- rigonkulous 6mo agoIts one of those extremely valuable life-changing hacks that kids who grew up in the 70's with electronics magazines as their primary source of tomfoolery knew all about .. and got into trouble for .. once or twice lets say .. during particularly heated typing classes on selectric machines of the 80's necessitating a headphone distribution mixer for sane memo-taking lessons, with a few crossed wires worth of feedback generation device introduced surreptitiously one particularly memorable summer Friday afternoon - originally intending to impress the girls of the class - not deafen them (albeit temporarily) .. but, in any case, getting the party started early, nevertheless.. (If you are going to attempt this with stereo headphones, keep the streams separated at all times!)
- me_jumper 6mo agoThis needs a (2017), I was so confused why this was published again, seemed so familiar.
- saagarjha 6mo agoFixed
- deleted 6mo ago[deleted]
- jpc0 6mo agoA magnet in a coil operates both ways, this is non intuitive but perfectly sound. Not sure if it's mentioned in the article but microphones can be speakers too...
- bigbugbag 6mo agosame with solar panels, they can be reversed to emit light.
- kqr 6mo agoWhat's their spectrum?
- DoctorOetker 6mo agonear infrared
- d3Xt3r 6mo agoSame with LEDs, they can be reversed to generate electricity.
- amelius 6mo ago[flagged]
- docjay 6mo agoWhat’s wild is that most things having to do with light, magnetism, and/or electricity are interchangeable and reversible. Put electricity through a wire and it’ll create a magnetic field, or wave a magnetic field near a wire and it’ll create electricity. That means that putting electricity into an LED creates light and a magnetic field, or putting light into the LED creates electricity and a magnetic field, or waving a magnetic field near it will create electricity in the wires and light from the LED. Granted for that last one you’ll need a spinning magnetar nearby, or just add some more wire to the LED and it becomes a kitchen counter experiment. Same interchangeability with solar panels, transformers, thermoelectric devices, etc. The effect might be big or small, depending on the setup, but the physics is happening either way. I’ve spent time lost in space thinking about how much stuff is really just a copper wire in various configurations. Have a copper wire - it’s an antenna, magnet, inductor, fuse, thermometer, heater, and strain gauge. Put another copper wire near it - it’s a capacitor. Curl one more than the other - it’s a transformer. Put iron on it - it’s a thermocouple. Put electricity through it - it’s a peltier cooler. Add salt water - it’s a battery. Put electricity through it - the iron is now a permanent magnet. Wave the permanent magnet near it - it’s a generator and a microphone. Put electricity through it again - it’s a motor and a speaker. Heat it up and it’ll make Cuprous Oxide - it’s a solar panel and a diode. Put electricity into it - it’s an LED.
- dickfickling 6mo agoI have vague memories of iPod Linux (or Rockbox, I can’t remember) having a feature where you could record voice notes using your regular headphones using the same technique
- m4lvin 6mo agoOkay, but how do I use this as a replacement when the mic is not working on Linux?
- GlumWoodpecker 6mo agoYou can use the `hdajackretask` program in the `alsa-tools` package to retask your jacks. https://github.com/alsa-project/alsa-tools/tree/master/hdajackretask https://github.com/alsa-project/alsa-tools/tree/master/hdaja...
- userbinator 6mo agoNot all speakers work well as dynamic mics; and in fact turning on mic mode may enable the bias voltage, which could either burn out the voice coil or hold the diaphragm against the stop, making it even less likely to pick up any sound. Jack retasking, although documented in applicable technical specifications, is not well-known, as was mentioned by the Linux audio developer This could be a "bubble effect"; the Realtek codecs mentioned have a Windows utility to configure the jacks, which countless otherwise non-technical users would've seen and interacted with, so awareness of this feature is probably higher than they think. Fun fact: the "ALC" prefix in their codec names stands for Avance Logic, which was acquired by Realtek and they just kept that prefix well into the HD Audio era.
- villgax 6mo agoIf this or an accelerometer based recording is what Meta uses to eavesdrop on in-person talk then color me pink
- murderfs 6mo agoIt's pretty unlikely that Meta is actually eavesdropping on your conversations, because it'd be immediately obvious from battery usage. The ability to turn speakers into microphones doesn't help if the speakers aren't actually connected to an ADC, and both of the modern smartphone OSes limit you to on the order of hundreds of samples per second, so it's rather difficult to get anything sensible without either doing a bunch of local analysis or exfiltrating it, both of which would be visible.
- slow_typist 6mo agoIt can be done with neural networks [1]. Also, speech doesn’t need much bandwidth to be intelligible. You would need control of the analog filter between the accelerometer and the ADC. With 250/s acceleration samples you can reconstruct a signal of a bandwidth of more than 100 Hz anywhere in the spectrum. That is called undersampling. [1] https://dl.acm.org/doi/abs/10.1145/3478102 https://dl.acm.org/doi/abs/10.1145/3478102
- maqp 6mo agoSome DJs use this principle when they need a hacky stage mic. They plug their headphones to the mixer's mic input, and shout to the speaker element.
- lelandfe 6mo agoE.g. this music video (evoking old Just Jam sets): https://www.youtube.com/watch?v=_xQKWnvtg6c https://www.youtube.com/watch?v=_xQKWnvtg6c To really take it to that next level, snap the headphones in half when you get up on stage for a lollipop. Even seen one bring a corded phone and cradle to a set.
- AmmarSaleh50 6mo agodon't let the CIA see this one
- Se_ba 6mo agoTbh it's crazy that you can do it in some of the microwaves
- rf15 6mo agoAs a kid I accidently plugged a mic into the speaker port and was surprised that, when I put my ear close to the mic, I could hear the computer sounds! It made sense in hindsight, and since then I knew they are kind of functionally equivalent.
- fipar 6mo agoMy first “electric guitar” as a kid was my acoustic with an earphone taped to the bridge and plugged to the mic in of my boom box. It was also my first “fuzz pedal” because the sound never came out clean :)
- VladVladikoff 6mo agoWhen I was a teenager I was friends with an extremely poor kid who literally lived on the wrong side of the tracks. He couldn’t afford a microphone and used an old pair of busted headphones to rap into as a microphone. He had recorded and produced a whole album like this with Fruity Loops on an old computer he found discarded at the side of the road.
- gfiorav 6mo agowhat happened to him?
- nullsanity 6mo agoWhat do you think? He was poor in America, so he stayed poor in America. 99.999% of stories about people in hopeless poverty end with them in hopeless poverty. To expect otherwise is ludicrous.
- Evidlo 6mo agoWow, what are the odds you were friends with him too!
- IncreasePosts 6mo agoHe ended up producing a documentary you can watch, called 7 Mile.
- metrix 6mo agoSo authoritative! You had me for a second :)
- QuercusMax 6mo agoMy little brother and I did this with an old Panasonic tape recorder. We were in elementary school so it wasn't very good, but it got my brother into music production.
- dustractor 6mo ago
- nailer 6mo agoVault 7 from wikileaks confirmed that yes, the CIA is using this.
- deleted 6mo ago[deleted]
- Anechoic 6mo agoThis is how drive-thru kiosks work (principal, not the specific implementation). Source: I used to measure the “microphone” frequency response for a kiosk OEM.
- angg 6mo agoThis comment caught me off guard and I couldn't believe this to possibly be true but as it turns out, yes, drive-thru speakers used the *literal same physical membrane* to act as both the speaker and microphone, and this was apparently widely commonpractice as recently as the 90s. And they literally just used off the shelf, bog standard stereo speakers to use as a mic. Insane. Given that such a mic would be several feet from the driver and poor audio quality could directly result in daily lost revenue for this business that sees revenue 100x to 1000x more than even high end audio equipment during this time period every month, I would've assumed they would've at least used a special membrane or more optimal type of speaker, but apparently not. Sidenote: Obviously I used an LLM to research this (not to write, this is all certified organic human-generated text), and I just gotta say, isn't it absolutely delightful to be able to satisfy such random, obtuse curiosities like this one on a whim? This kind of question would've normally required a fair bit of googling to confidently validate, to the point I most likely wouldn't have even attempted to do so.
- userbinator 6mo agoMany intercom systems and walkie-talkies do the same. The downside is they're half-duplex.
- riobard 6mo agowhy is jack retasking a thing…
- adrianmonk 6mo agoChips only have a certain number of pins. It probably works out better economically if those pins can be used for either input or output. Chip manufacturers can thus make one product that will fit the needs of more customers instead of (say) 9 different chip variants with 8 inputs and 0 outputs, 7 inputs and 1 output, 6 inputs and 2 outputs, etc. It could also be useful to the end user. Motherboards have a limited number of ports since the connectors cost money and take up space on the back panel. One user might want a line input (for digitizing old cassettes, for example)[1] and another user might want an extra surround sound output (for 7.1 surround sound instead of just 5.1 surround). With retasking, the motherboard can support both these niche use cases with a single shared port. --- [1] You can't use a microphone input for this because (a) it's mono and (b) it's a different voltage level.
- analog31 6mo agoA fun fact is that the ability of a single transducer to function as both a speaker and a microphone is the basis for establishing an absolute measurement of sound pressure. https://nvlpubs.nist.gov/nistpubs/jres/25/jresv25n5p489_A1b.pdf https://nvlpubs.nist.gov/nistpubs/jres/25/jresv25n5p489_A1b....
- antirez 6mo agoSimilarly most leds are photo diodes, electric motors can be used to generate current, Peltier cells can be used to generate current, and so so forth. Many of such physical processes are invertible.
- jimmydddd 6mo agoYes. Mostly the same basic components--Just optimized for which direction you are going in. I recall using an single in ear speaker as a microphone as one of the experiments in my Radio Shack 101 eperiments electronics kit.
- anonymousiam 6mo agoWhile staying in a high-end D.C. area hotel, I once discovered a hidden hard-wired speaker under the bathroom sink. Somebody had written "F.B.I." on it with nail polish. I already knew that speakers could be used as microphones, and it occurred to me that putting a speaker in a hotel room in the name of "safety" would be a great cover story for a surveillance operation.
- jnellis 6mo agoWhen I did commercial fishing in Alaska, often the boats just had two speakers, one in the wheel house and one on the deck (long liner). You just talked into/toward the speaker.
- jedbrooke 6mo agoFun fact, an electric guitar can also be used as a microphone if you shout in to it loud enough. We discovered this while fooling around with some guitars and such as teenagers. We had a 4 track input device that was separating vocals and instruments, but even after turning down the vocal track, we could still hear it in the instrument track. We then of course followed it up with some experiments deliberately shouting into the guitar and enjoying the distorted recordings that came out of it
- olelele 6mo agoA big speaker element is useful for micing kick drums.
- ssttoo 6mo agoIt was so popular in studios to use an old Yamaha ns10 speaker as a kick (bass) drum mic that now Yamaha started making and selling an “official” version. I personally used a toy guitar amp for this purpose https://music.stoyanstefanov.com/2017/03/30/diy-sub-kick-mic/ https://music.stoyanstefanov.com/2017/03/30/diy-sub-kick-mic...
- alexjplant 6mo agoUsing a speaker as a kick drum mic ("subkick") has been a thing in recording for years [1]. I've never used one but it makes complete sense. [1] https://bobbyowsinskiblog.com/build-subkick/ https://bobbyowsinskiblog.com/build-subkick/
- ChicagoDave 6mo agoI used my moms Koss headphones as a microphone on her old stereo and used it to broadcast cast my teenage stupidity to the whole house.
- DoctorOetker 6mo agonot only can electromagnet voice coils (speakers or microphones), be used as either a speaker or a microphone (transducer), they can even be used as both at the same time using a DC-coupled circulator / isolator: https://techlib.com/files/rfdesign3.pdf https://techlib.com/files/rfdesign3.pdf
- undebuggable 6mo agoThat's all true. As a kid I was watching with sister a children's show in TV. The actor on the screen asked a question followed by silence. My sister yelled the answer at the TV, then the actor said something like "you're right kid". I was flabbergasted.
- kQq9oHeAz6wLLS 6mo agoThis also works during televized sporting events. The refs can indeed hear you, but you have to yell pretty loud.
- undebuggable 6mo agoAh so that's why they're going it! In front of TV I always feel like the dumbest person around.
- p1mrx 6mo agoDora the Informer.
- f055 6mo agoAs a kid behind the Iron Curtain I had a radio & cassette tape player with a single large speaker built-in. The cassette player had a record button that when pressed together with play used the speaker and I could actually record my voice, and play it back, from the tape. After enough re-recording on a single tape the fade of the old recordings broke through the new ones creating a truly amazing sound experience. Too bad I lost the tapes and the device.