This Optical Microphone Can 'See' a Sound by Filming its Vibrations

Researchers from Carnegie Mellon University in Pennsylvania, USA, have developed a camera system that can “see” a sound by filming its vibrations. These vibrations can then be used to reconstruct sound with purity and fidelity, enabling the capture of isolated audio with no interference, and no microphone. Beyond the system’s technical prowess, it opens up a world of potential possibilities. To be able to “see” sound, the scientists have developed a camera system capable of capturing the slightest sound vibration with high precision. Composed of two cameras and a laser, the imaging device allows the researchers to visualize what’s usually invisible to the naked eye. The captured sound can then be reproduced in a clear, pure way, with no interference or ambient noise.

To demonstrate their discovery, the researchers managed to capture isolated audio of separate guitars playing all together and individual speakers playing different music at the same time. As part of their experiments, they analyzed the vibrations of a tuning fork, as well as those made by chips packet placed near a speaker.

The dual-camera set-up, which uses two ordinary cameras, produces high-quality recordings and is capable of capturing vibrations from objects in motion. The system works by analyzing speckle patterns in the captured images. This is the way light behaves in space after being reflected from a rough surface. An algorithm then calculates the difference between these patterns and converts them into vibrations to reconstruct the corresponding sound.

This optical microphone effectively allows us to “see” otherwise invisible vibrations and opens up new perspectives in potential applications. It could prove revolutionary for sound engineers, for example, who could have a band or orchestra play together while monitoring each instrument individually. Another possible application could be the monitoring of industrial machinery, so that a suspicious noise — otherwise imperceptible to the ear — could be investigated in the aim of pre-empting maintenance.

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