The burgeoning podcasting biz wants to put this bug in your ear: The audio-entertainment format has strong momentum, with advertising revenue in the U.S. alone set to jump 85% this year, according to a new PwC study.

There’s an important caveat, though: The study was underwritten by nine companies that each have a financial interest in podcasting. The firms are Acast, Podtrac’s Authentic, Gimlet Media, HowStuffWorks, Market Enginuity, Midroll Media, Panoply Media, Public Media Marketing (PMM), and Wondery.

Furthermore, while podcasting is on a growth trajectory, it remains much smaller than other media sectors such as film, TV, music or video games. U.S. podcast ad revenue is set to top $220 million in 2017, compared with $119 million last year, according to the study released by the Interactive Advertising Bureau and conducted by PwC U.S.

For the study, PwC surveyed 20 of the largest podcast companies, including publishers and ad networks. The revenue estimates for 2017 are based on participating companies’ self-reported revenue forecasts, rather than actual results.

“These findings confirm that podcasting is experiencing impressive year-over-year growth, and we can expect even more gains on the horizon,” PwC US partner David Silverman said in a statement. “The study also identifies key trends that should be on marketers’ radar screens.”

Among other the study’s other findings:

  • Advertisers prefer ads read by podcast hosts rather than spots that are pre-produced with a different announcer;
  • In 2016, podcast publishers generated more revenue from dynamically inserted ads for the first time.
  • Direct-response ad campaigns continue to be the most prevalent campaign type, although both brand-awareness and branded-content campaigns increased from 2015 to 2016.

Pictured above: The title card for “S-Town,” the podcast series from Serial Productions and “This American Life.”