Privacy is a placement problem

Privacy on a wearable recorder is usually solved like this: add a light, write a policy, and ask you to trust us.

Those three things have something in common — every one of them can be changed by a firmware update, and you would not know.

Two microphones and a subtraction

The main mic is at the bottom centre of the left rim, port facing down at your mouth, 4 to 7 centimetres away. The reference mic is at the top corner of the right rim, port facing up and tilted back, away from your mouth, about twelve centimetres away.

When you speak, your voice arrives at the main mic 7 to 9 dB louder than at the reference mic. When somebody half a metre away speaks, they are almost exactly the same distance from both, and the difference collapses to under 1 dB. The firmware puts the threshold at 4 to 5 dB, and anything below it is never written to storage.

No DSP, no beamforming, no voiceprint, no model, and not one cent of extra cost. The entire privacy design is the position of two holes and one subtraction.

Why it cannot be switched off

This is where the value of the approach actually is. Those 7 to 9 dB are not generated by software; they are decided by the mould. The two microphones sit at different distances from your mouth, so your voice is naturally louder in one of the two signals.

Somebody half a metre away is essentially equidistant from both. Their voice is equally loud in both signals. No matter how the firmware is written, there is no difference there to exploit. Recording the person next to you would take a different pair of glasses, not a different build of firmware.

A promise that can be switched off is not a guarantee. A geometry that cannot is.

What it costs, said out loud

The other side of the same decision is that this pair cannot record a meeting. A few people brainstorming, an interview, a lecture — it cannot do those, and that is what a voice recorder is for.

We are not going to hide that. A device that records only you and a device that records the whole room are two different products, and anybody who is clear about which one they want will not buy the wrong one.

Online meetings are the exception, and a very good one: if you want your own contribution to a call kept separately, this is exactly right — what gets recorded is the part you said, with nobody else's voice in it.