Content is king. Bill Gates coined the phrase in 1996, but it still holds true today in the world of digital marketing. Investing in quality content helps build a relationship with consumers, hopefully turning them into loyal return customers rather than one-hit shopping wonders. But as many content marketers focus on creating branded articles and social media schedules, many are overlooking an alternate format: audio.

Podcasts aren’t new—they’ve been around since the early 2000s—but they are experiencing a renaissance attributed to increased smartphone adoption and huge commercial successes such asSerial” and “This American Life.” In 2016, podcasts had 57 million monthly listeners, according to consulting firm Activate Inc., and that number is growing.

As technology improves, David Toop, professor of audio culture and improvisation, expects sound will even overtake the screen. “Our cultural understanding of listening and of sound will change, we’ll shift from being a visio-centric culture to one more focused on sound and hearing,” Toop told Spotify.

Given the large, enthusiastic audience and low upfront costs, marketers have to think seriously about getting their own voices heard on this powerful medium.

Intimate and Ample

Streaming audio content is immersive and intimate—the closest thing audiences have to a confidential conversation with close friends.

Even better: Most people (79%) consume audio content in places where visual media can’t reach them—like the car. That makes podcasts a unique opportunity to reach busy, on-the-go consumers. And with 380 million internet-connected cars expected on the road by 2021, that opportunity is growing.

Xbox HUNTs the TRUTH

Brands are already capitalizing on sponsored podcasts, going well beyond sponsoring ads at the beginning of a segment. The success of Microsoft XBOX’s “Hunt the Truth” shows just how far a brand can go to reach an audience with audio. XBOX and 343 Industries, the makers of the popular Halo gaming series, used the podcast format to generate excitement ahead of the release of “Halo 5: Guardians.” Partnering with the Ayzenberg Group, they devised “Hunt the Truth,” a 22-part audio series that follows fictional journalist Benjamin Giraud as he conducts his own investigation into the game’s Master Chief. The story turns sinister when Ben uncovers evidence of the biggest government coverup in Halo history.

Listeners were hooked. The podcast attracted over 181 million impressions, 1 million social interactions and 2 million Halo 5 mentions on social media. “Hunt the Truth” appeared in iTunes’ Best of 2015 podcast round up, and Halo 5 jumped from the No. 5 to the No. 1 most anticipated game in the month following the campaign launch.

One Size Does Not Fit All

Sponsored podcasts are as diverse as the brands they serve. GE’s “The Message” is an eight-episode sci-fi thriller that incorporates the company’s work in science and technology into the story line without mentioning it by name. On the other end of the spectrum,  UBS’ “Top of the Morning” is a 10-minute newscast featuring top analysts and strategists talking about economic and financial issues. The content of these podcasts are in line with the brand’s vision, but don’t require an overt sell.

Specialists are Sprouting Up

Gimlet Media, a Brooklyn-based podcast company, is making waves in branded podcasts. In addition to putting out original shows, the company also partners with brands to produce a wide range of sponsored content. Recently,they partnered with Tinder to produce a podcast about the trials and tribulations of dating, cleverly titled “DTR,” Millennial shorthand for “define the relationship.”

Nicole Wong, a producer at Gimlet Creative, said podcasts provide a unique and intimate storytelling experience. “People tend to listen to podcasts when they are alone, so they feel really connected to the hosts and stories they’re listening to,” she said. “Brands have really interesting stories to tell, and by utilizing this intimate medium, advertisers have a profound opportunity to humanize their brand.”

Looking Ahead

New technologies are make audio content even more promising. In 2017, customers are expected to buy 24.5 million voice-first devices, such as Amazon’s Alexa and Google’s Home, an exponential increase from 6.5 million in 2016. These products bring a new level of audio awareness to the home.

Despite the promise, many marketers are hesitant to wade into the podcast waters because it can be difficult to measure return on investment. Podcast metrics are limited to subscribers or downloads, but it’s impossible to tell how long people listen. One workaround is to embed the podcast in a landing page in order to track both pageviews and time spent on site. Closely following social interactions is another way of measuring whether a podcast is striking a chord with listeners. For brands that want to connect more closely with consumers and tell interesting stories, there aren’t many excuses beyond fear of the unknown.