A DIY laser mic project has resurfaced online, harking back to espionage favourites of the KGB during the Cold War, though with modern twists.
The core concept directs a laser onto a window, picks up the light reflections and identifies vibrations from conversations inside the room, employing a 3D-printed stabilised sensor mount.
It uses a visible laser and a repurposed amplifier circuit from an old mic, swapping the capsule for a photodiode, with a polarising filter to reduce ambient noise, though two sensors could provide completely clear audio.
While the current output is a little noisy, with some refinement it could achieve crystal-clear conversation reconstructions, according to Hackaday.
