The Visual Microphone: Passive Recovery of Sound from Video
Why Hacker News recommends it
HN commenters cite it as the classic demonstration of audio recovery from video in surveillance and privacy discussions.
What it is
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.
Recommended by 1 HN commenters across 1 different months, 2015 to 2026.
What Hacker News said
Recommends eesmith · 2017-12 · on “Prostitution cases dismissed because cops’ cameras mistakenly recorded audio”
"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 [this video] . High-speed camera is best, but at the end they show how a regular consumer-level camera can also be used.
Cites lawry · 2015-03 · on “Periscope by Twitter”
Remember even if you mute your microphone, it's still possible to extract audio from the video you are streaming: [this video]
Cites anfractuosity · 2018-01 · on “If you watch closely enough, everything is a speaker”
See this - [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?
Cites ehsankia · 2018-10 · on “Show HN: Lipreading with Deep Learning”
You can do it with video too, even: [this video] Also, this is only tangentially related, but you can also see through walls using WiFi: [LINK]
Cites bbbobbb · 2020-07 · on “Spies can eavesdrop by watching a light bulb's vibrations”
Here similar experiment, 6 years ago: [this video] If you think that actual government agency cannot do even more easily with better equipment in 2020 you're kidding yourself.
Cites spyder · 2026-02 · on “WiFi Could Become an Invisible Mass Surveillance System”
with a high speed camera any vibrating reflective object like a potato chips bag can become a microphone: [this video]