As investment in digital audio advertising continues to grow, Google’s DoubleClick Bid Manager is rolling out support globally for buying audio ads programmatically across a handful of streaming services. The company announced Wednesday that advertisers can now buy ad inventory programmatically from Google Play Music, Spotify, SoundCloud and TuneIn, and soon Pandora.

In the US last year, digital audio ad revenues topped $1.6, according to the IAB, an increase of 39 percent over 2016. Mobile accounted for roughly 75 percent of digital audio ad revenues in 2017.

“We are thrilled to see DoubleClick embracing programmatic audio. This launch makes it possible for Bid Manager customers to reach Spotify’s highly engaged audience across video, display and audio formats,” said Zuzanna Gierlinska, head of programmatic, Europe at Spotify in a statement.

The supported exchanges for audio ads are DoubleClick’s own Ad Exchange and Rubicon. DoubleClick Ad Exchange is the inventory provider for Google Play Music.

Advertisers can upload .mp3 audio spots in a variety of lengths, including 15- and 30-seconds and an optional companion image or HTML5 asset to display around the publisher’s audio player.

DBM uses the Video Ad Serving Template (VAST) standard to serve audio ads. Advertisers are not able to use third-party VAST tags, but can include a registered Universal Ad ID in VAST tags.

Reporting metrics include audio completion rates, listen rates by quartile, mute and pause rates, Audio Media Cost eCPCA (media cost/completes), impressions and clicks on the companion creative and more.

In terms of pricing expectations, “Rates for audio placements are significantly higher than the rates for standard display impressions. We recommend setting CPM rates for audio with the same strategy you’d use for video inventory,” says Google in its support pages.

Programmatic firm MightyHive tested digital audio ad buying through DBM to extend the reach of a CPG client’s radio campaign aimed at driving awareness. Ads were targeted by DMA and age group. MightyHive says the test flight yielded 7.5 million impressions and over 7,500 clicks across mobile web, desktop and app with completion rates above 95 percent and a CTR on companion creative of .11 percent. If that CTR doesn’t sound impressive, consider it’s about twice the rate of the typical banner campaign.