https://techcrunch.com/2019/04/01/pandora-to-test-interactive-voice-ads-later-this-year/

Radio ads broadcast a message to listeners, but Pandora’s new voice ads will allow listeners to respond by speaking aloud – either to get more information about the product being advertised, or to skip the ad if it’s not of interest. The company confirmed it has an agreement to test interactive voice ads where listeners engage by speaking back to the ad. The test will be powered by the San Francisco-based ad tech company, Instreamatic, and will launch into beta sometime later this year.

Unlike web and mobile ads – which can be measured through things like impressions and clicks – traditional audio ads aren’t clickable. That means advertisers don’t know for sure how many people who heard the ad later went seek out more information, or make a purchase.