Apple is working on a technology to enable in-ear headphones to be controlled via the minutest facial expressions. This project, revealed by a patent application Apple has filed with the US Patent Office, could come in useful in many different ways.

Apple's approach, which is detailed in the patent application, describes a point of light that is projected by the headphones on to a specific point on the head. With the help of 'interferometry' sensors, the headphones will be able to recognise and interpret movements in the user's face, including changes in facial expressions as well as silent mouthed speech.

With the help of the sensors, not only the movements of the facial muscles could be registered, but also vibrations of the skin, for example when speaking loudly or mute. So, in theory, you could give the Siri voice assistant a command without saying it out loud.

Aside from entering commands, this technology could be used to identify the user. Bio-identification could be used to build in a further level of security to prevent unauthorised use of the devices.

If and when the technology will find its way into an Apple product is unclear - it seems a long shot for this to make it in the next AirPods, which are expected as early as spring 2021. There have been rumours since as the summer, however, that the AirPods Studio could have gesture support.

Apple researches in many directions and repeatedly applies for patents, but not all of them make it to market.

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This article originally appeared on Macwelt. Translation by David Price.