Investors are warming to podcast companies, with a flurry of funding rounds in recent weeks worth more than $70m — a sign that the digital audio industry is converting listener buzz into revenue-generating businesses.

Acast, the Swedish podcasting company that hosts publishers including the Financial Times, the Economist and Vice Media, is the latest to receive backing, raising $19.5m from investors led by Swedbank Robur and Norron Asset Management and bringing its total funding to $32m since 2014.

Gimlet Media raised $20m from investors including WPP, the world’s largest advertising group, the New York growth equity company Stripes Group and Laurene Powell Jobs’s Emerson Collective. The round reportedly valued Gimlet at $55m pre-money.

Another podcast producer, HowStuffWorks, received a $15m infusion from Raine Group, the boutique investment bank. Cadence13, which hosts the popular political show Pod Save America, sold a 45 per cent stake for $9.7m to Entercom, the US radio broadcaster. Podcast network Art19 raised $7.5m from investors including Bertelsmann’s digital media fund and Hollywood’s United Talent Agency.

“The amount of incoming requests from the world’s largest VC companies is getting bigger every day. It used to be one every few weeks. Now there’s a couple every day,” said Måns Ulvestam, Acast co-founder and chief executive.

Investors are attracted to a surge of interest from consumers and advertisers in recent years, as more people shift to consuming media on demand. In the US, 67m people — nearly a quarter of the adult population — listen to podcasts every month, up 21 per cent from a year ago, according to Edison Research.

“I do think that this [investment] is a sign of the industry being taken seriously for what it is and what it can be, and that comes after a somewhat noticeable one-to-two-year lag,” said Nicholas Quah, founder of Hot Pod, a podcast industry newsletter.

A PwC study of the US podcast market, funded by some of the industry’s biggest players, including Acast, Gimlet, and HowStuffWorks, projects that advertising revenue will jump 85 per cent to $220m in 2017.

Ad spending is ballooning as big brands have begun to dip their toe into podcasts, which have thus far been mainly funded by direct-response advertisers. Companies such as Gimlet and Panoply, the podcast company owned by digital publisher Slate Group, have launched branded content divisions that create ads and even entire podcasts for advertisers.

“Investors have noticed that a lot of big brands have come into the space and there are real businesses being built,” said Matt Lieber, co-founder and president of Gimlet. “Ford Motor and Gatorade and Apple and Dell are all customers. Investors take notice of that. You’re seeing scaled audiences and now you’re beginning to see scaled revenue.”

That spending is poised to accelerate further with Apple rolling out detailed listener analytics in its latest operating system update. That will allow podcast creators to offer better information to advertisers on how people consume individual episodes, and their embedded ads, on Apple’s podcast app, the most popular platform.

Acast said it will use its new funding to invest in its technology, to grow its US business and to expand to additional international markets.

“The streaming audio market is worth $33bn every year. No one sits in front of the radio waiting for their favourite song to play. They just go to Spotify or Apple Music,” said Karl Rosander, Acast co-founder and chief strategy officer. “What’s left is spoken word. The money will funnel to where the audience goes, and as long as podcasting continues to grow, that’s where the money will go.”

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