Pandora is expanding the scope of its interactive voice-based advertising today, launching the service in beta for more listeners and advertisers while adding a new tool that enables free users to access premium features when they use their voice. The launch comes as audio-streaming platforms and advertisers seek new ways to monetize listeners through deeper engagement, which is also easier to measure.

Pandora, which was acquired by SiriusXM for $3.5 billion nearly two years ago, launched an early-stage pilot for interactive voice ads back in December that was designed to bring two-way engagement to brands. For example, an advertiser trying to sell beds could ask the user whether they would like to hear tips on how to get a good night’s sleep, to which the listener could respond “yes” or “no.”

Brands on board for the beta launch include AT&T, Doritos, KFC, Lane Bryant, Purex, Unilever, T-Mobile, the Home Depot, Volvo, Xfinity, Acura, among others.

Additionally, Pandora will also now allow users to unlock on-demand music search with their voice, a feature that is usually reserved for those on a Premium paid subscription. “Premium access” is an existing feature that allows ad-supported users to gain temporary access to on-demand music, if they agree to watch a video advertisement. Now this feature is extending to voice search, meaning free users who search for a specific track with their voice will be invited to watch a video ad. If the user responds with an affirmative, the ad will play, followed by the requested song. If the user declines, the original (not on-demand) music content will continue to play.

Interactive voice ads are built on Pandora’s voice assistant, called Voice Mode, which launched exactly one year ago today. Similar to Alexa, Siri, Google Assistant, and the like, Voice Mode responds to a command (“Hey Pandora”) and natural language requests, such as “play something different” or “add this song to my BBQ playlist.” Pandora users who opt into Voice Mode through their app’s settings will automatically have access to interactive voice ads.

It’s worth noting that the interactions within the voice ads are currently pretty basic and are restricted to simple yes or no responses, along with variations such as “sure,” “why not,” and “okay.”

“We are starting with a very simple ‘yes/no’ format as listeners get used to hearing and interacting with voice ads,” Claire Fanning, VP for ad product strategy at Pandora, told VentureBeat. “It’s a totally new concept to them, so we need to keep it simple as this behavior modifies.”

In the future, such ads could become more conversational to solicit feedback on products and brands and perhaps feed into broader market research campaigns, though Pandora’s plans might not evolve in precisely this direction.

“The possibilities are endless, but we are sensitive to the fact that we are asking consumers to implement a new behavior,” Fanning added.

Measurement

Spotify has also been dabbling with interactive voice ads, kicking off a test with Unilever last year, while the Pandora rival last month launched an interesting new initiative in the U.K., allowing listeners to interact with audio ads from cosmetic company Nars to request product samples directly to their home.

It’s clear there is a growing push to make audio-based advertising more engaging and lucrative, particularly with podcasts continuing to surge in popularity. To make audio advertising more alluring to brands, it needs to become more measurable, similar to the way “clicks” and “taps” can be monitored in screen-based advertising. Just because an audio ad is playing doesn’t mean anyone is actively listening to it, which is why soliciting vocal input from the user could help streaming platforms such as Pandora and Spotify increase advertising spend.

More than that, audio-based advertising is often a hands-free experience, with the user perhaps sitting on the other side of a room or simply not looking at a screen. Being able to engage a listener at a distance, as they paint their ceiling or drive to work, opens up a whole world of opportunities.

This article was updated to clarify the distinction between interactive voice ads, and on-demand voice search which requires the user to watch a video advertisement.