The podcast market is booming. Here are 5 audio firms that could be acquired next and who might buy them.

Media companies are chasing the podcasting market.

Spotify has been snapping up podcasts while reports swirl about Amazon eyeing podcast content company Wondery, the podcast giant behind shows like "Dirty John."

And with the Interactive Advertising Bureau estimating the podcast ad market will hit $1 billion this year, others are looking at companies to help boost their podcast advertising. These include firms that plug ads into podcasts and make original content that they can sell to media companies and advertisers.

Podcasting has reached a critical mass with listeners, and the advertising is starting to catch up, said Jonathan Keith, founder and CEO of creative agency Feelr Media, which makes branded podcasts for brands like Microsoft. "With dynamic ad insertion and programmatic, they're going to have real metrics and it's been a very hot area."

Spotify in particular has been an aggressive acquirer, just agreeing to buy podcast advertising firm Megaphone for $235 million, and Joe Rogan's popular podcast. Spotify also owns Gimlet Media and Anchor. IHeartMedia recently entered an agreement to buy Voxnest, a podcast analytics and programmatic advertising firm, and satellite radio company SiriusXM bought podcast company Stitcher for $325 million in July.

Nick Quah, who writes podcast email newsletter Hot Pod and critiques podcasts for New York Magazine, said that it will be hard for any company to beat Spotify's podcast acquisition spree.

But Apple, Google, and Amazon are also likely podcast acquirers because they're betting on making audio content more mainstream and baking podcasts straight into smart speakers and devices, said Eric Franchi, operating partner of MathCapital, a venture capital fund that invests in advertising and marketing companies.

Business Insider spoke with a handful of experts about what other podcast companies could be hot acquisitions, and they listed five. (To be clear, they did not suggest any are actually in talks.)