Sonos is getting serious about expanding beyond the home. The smart speaker maker was awarded a patent last week that provides the strongest evidence to date for Sonos-made headphones. Not only does the patent confirm that the company has been working on a long-rumored headphone product, it also mentions a number of possible features and outlines how it would integrate with existing Sonos speaker setups.

Bloomberg first reported in early 2019 that Sonos was looking to launch its own headphones, but the company had been able to avoid any subsequent leaks until now.

"As a company founded in innovation, we're always working on different ideas and innovations that can help the world listen better," a Sonos spokesperson said. "We continue to make investments in our strong patent portfolio with dozens of new patents each year. We do not have additional information to share at this time regarding our future product roadmap."

Sonos executives have for some time said that they were looking to launch products that work outside of the home. The company launched its first portable speaker, the Sonos Move, a year ago, and told investors at the time that it saw "significant opportunities" in the out-of-home market. An expansion beyond its existing smart speaker products could also allow Sonos to further diversify its business and add money to its coffers to sustain its legal fight against Google for alleged patent infringements.

The patent, which Sonos first applied for in September 2019, describes in detail how Sonos-made headphones might work and look. Images included in the filing show two possible designs for the company's wireless over-ear headphones. Judging from the filing, it is likely that the headphones will come with a noise cancellation feature that can be turned on and off, as well as one or more microphones for voice control. Sonos was the first smart speaker maker to support multiple voice assistants in its products, and the company is currently also developing a dedicated voice assistant for music control in-house.

It's not uncommon for companies to include features in a patent filing that won't make it into a final product, or describe a number of different implementations of the same feature. In this case, Sonos describes a number of different control mechanisms, including a knob extending from the headband as well as touch sensors, further signaling that the product will come with advanced control mechanisms for music streaming services. It also mentions a line-in port that could double as an interface for charging, as well as a possible USB-C charging port.

While many of the features mentioned in the filing are common for wireless headphones, one of the more interesting aspects is how the device might integrate with existing Sonos speakers through something the company calls a "swap."

From the filing: "For example, if a particular piece of content play is currently playing on the wireless headphone, a swap changes the playback to play that piece of content on one or more other playback devices on the local network."

This type of handover would make it easy for people to play music on their headphones while out and about, and then shift playback to their hi-fi system when they return home. Beyond this, it also indicates that Sonos is likely going to target its existing customer base for this new product. Sonos has long relied on repeat purchases from existing customers. In 2019, 37% of its newly sold products were registered by consumers who already owned at least one Sonos speaker.

Sonos has faced some economic pressure from the COVID-19 crisis, resulting in layoffs of 12% of its staff in June. The company has also been stepping up its fight against bigger competitors like Google and Amazon. It sued Google for alleged patent infringement in January. Last month, Sonos CEO Patrick Spence told Protocol that Amazon's practice of selling its Echo speakers below cost was illegal.

Updated: This post was updated at 12:22 p.m. PT to include Sonos' statement.