Sonos is yet to make a foray into the world of headphones, but two pairs of wireless earbuds have been spotted in patents, and they have a unique charging method.

Although over-ear Sonos headphones have been rumoured since 2019, it appears the multi-room audio firm is working on some all-the-rage earbuds, too. And they might have a feature not seen before.

The patent, spotted by Zats Not Funny, was published by the USPTO (United States Patent and Trademark Office) in February showing diagrams of two different earbud designs along with details of how they might work.

One design (above) shows an unusual charging case where the wireless earbuds attach at either end and are not enclosed as most true wireless earbuds are. However, it's charging and playback time that Sonos appears to be trying to win at.

Another image shows earbuds that have additional batteries that can be attached to the outside to extend battery life. The patent filing describes it as a “system for wireless earbuds involving charging adapters that are attachable to the wireless earbuds.”

Sonos wireless earbuds charging adapters

It seems that these button shape batteries will remain in the case until the earbuds get low on battery, then attach with magnets to give you additional playtime while still wearing them.

"the charging adapter is attachable to an external surface of an earbud using a magnetic or mechanical interface that align with electrodes of the charging adapter with electrodes on the wireless headset, allowing an internal battery of the earbud to draw current and charge from the charging adapter while the earbud is in-ear," says the patent.

It also explains that the system would offer three different modes. 'Normal' where the earbuds are in-ear but the adapters are in the case being charged, 'Active' where the adapters are attached to the earbuds and 'Passive' where everything is in the charging case.

Sonos has proven it can make Bluetooth products with the Move and more recent Roam speakers, but headphones remain a missing string from the firm’s bow. We would assume that the headphones will get similar features to the Roam such as Sound Swap which allows you to move music between devices.

Note that a patent listing is no guarantee of a product being launched commercially. Sonos has committed to two new products for 2021 so while it seems like headphones could be the second (following the Roam), it could well be the long-awaited over-ear model that arrives this year.

Diagrams showing a pair of over-ear headphones also appear in this patent listing.