Researchers from the Beijing Institute of Technology have created a microphone capable of recording sound through light. The prototype analyzes microscopic vibrations on the surface of objects using reflected light and can record speech even through glass windows.Its operating principle is based on encoding light in a spatial light modulator and registering changes with a photodetector. The main difference is the use of a single-pixel photodetector instead of complex cameras with millions of pixels, which makes the technology cheaper.
In experiments, the microphone successfully reconstructed speech and a fragment of Beethoven's For Elise from a distance of 0.5 meters. To improve accuracy, the researchers used algorithms based on the Fourier transform, which allowed the system to work with different surfaces. The technology is capable of "hearing" vibrations of various objects - from paper cards to plant leaves.
This microphone accurately reproduces low-frequency sounds up to 1 kHz, while high-frequency sounds require filtering. At the same time, it generates only 4 MB of data per second. While the microphone currently exists as a laboratory prototype, the researchers are already planning to adapt it for medical purposes, including monitoring pulse and heart rate.