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Only a slightly related tangent, but most headphones and other loudspeakers can be very effective microphones when wired into the right circuit. While speakers
by retrac 6y ago
Only a slightly related tangent, but most headphones and other loudspeakers can be very effective microphones when wired into the right circuit.
While speakers are often wired directly to a one-way DAC, that's not always the case. Sometimes the analog lines are all fed into a multiplexer and it can be routed to a ADC. Sometimes it's wired to a general purpose IO pin.
In such cases, reprogramming could turn that speaker into a microphone. I wonder if anyone has exploited this in the wild yet.
- jacquesm 6y agoYou can do the opposite of noise cancellation too: determine the back emf from the speaker compared to the audio input, that will give you the audio in the room. So you can use the same circuit both to drive the speaker and use it as a microphone. As good as undetectable until you trace the circuitry of what looks like an ordinary amplifier. The difference is on the order of a few mV but that's more than enough. My personal favorite is the laser attack that turns any shiny surface into a microphone. When it's not on it literally isn't there.
- layoutIfNeeded 6y agoNo need to use a laser if there’s an incandescent bulb in the room: https://www.wired.com/story/lamphone-light-bulb-vibration-spying/ https://www.wired.com/story/lamphone-light-bulb-vibration-sp...
- jacquesm 6y agoOh that's a neat one. Thank you for that link.
- rightbyte 6y agoIf you have noise cancelling there is allready mics right?
- jacquesm 6y agoIn this particular scenario there wouldn't be.
- mixermachine 6y agoMost bluetooth headphones already have a mic ^^. At least the ones I own and the ones I found after a short Amazon search.
- segfaultbuserr 6y agoSee SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit https://arxiv.org/abs/1611.07350 https://arxiv.org/abs/1611.07350 If you are a hacker who removed microphones from your computer but is worrying about this exploit, fortunately, a simple mitigation is possible - just put an audio amplifier or unity-gain buffer between the speaker and the audio output port, so the audio signal cannot travel back to the audio chip. Any "Hi-Fi" headphone amplifier can be used, but a $0.5 opamp is enough - a daughterboard can be tiny enough to fit inside a laptop.
- deleted 6y ago[deleted]