The Visual Microphone: Passive Recovery of Sound from Video
Abe Davis's Research1 HN recommenders · 2015–2026
1.9M views · demo · evergreen · Uploaded 2014-08-04
MIT researchers show that sound can be recovered from silent video by analyzing tiny vibrations in objects such as a potato chip bag. It works even with consumer cameras by using rolling shutter.
HN commenters cite it as the classic demonstration of audio recovery from video in surveillance and privacy discussions.
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6 comments from Hacker News
Remember even if you mute your microphone, it's still possible to extract audio from the video you are streaming: [VIDEO]
"security cameras outside of stores" would be in public areas, yes? The Lifehacker link you pointed to says "Generally speaking, you have the right to record video in all public spaces without need of consent." Now for the fun part - it can be possible to extract audio from video, by careful processing of the small motions the sound induced in objects in the frame. See [VIDEO] . High-speed camera is best, but at the end they show how a regular consumer-level camera can also be used.
See this - [VIDEO] They show audio captured from a 60fps video from a DSLR exploiting the rolling shutter. I'm not sure if you can use less than 60fps though?
You can do it with video too, even: [VIDEO] Also, this is only tangentially related, but you can also see through walls using WiFi: [LINK]
Here similar experiment, 6 years ago: [VIDEO] If you think that actual government agency cannot do even more easily with better equipment in 2020 you're kidding yourself.
with a high speed camera any vibrating reflective object like a potato chips bag can become a microphone: [VIDEO]