Bone Conduction Sensor

A bone conduction sensor is a device that detects voice through vibrations that travel through bone. If you plug both ears with your fingers and speak, your voice sounds like it's echoing inside your head — that's because the sound is traveling through your facial bones and skull rather than through air. A bone conduction sensor captures these bone vibrations and converts them into voice.

A regular microphone picks up sound spreading through the air from the mouth, so it also picks up nearby voices or passing traffic noise. A bone conduction sensor, on the other hand, sits directly against the wearer's bone, so it only picks up the vibrations created when that specific person speaks. This means it can capture the wearer's voice relatively cleanly even in a noisy cafe or on the street.

However, a bone conduction sensor alone struggles to reproduce voice perfectly. Since vibrations transmitted through bone are mostly low-frequency, it's usually paired with a regular microphone to fill in the rest of the sound.

In an article about RayNeo's iO Glasses, it was introduced that "voice recognition is handled by four microphones and a bone conduction sensor." What's easy to confuse here is that this bone conduction sensor is not a device that plays sound, but an input device that captures the wearer's speech. While the commonly known bone conduction earphone is an output device that transmits sound through bone to the ear, the bone conduction sensor works in the opposite direction — reading bone vibrations to recognize voice.