Phone calls are hot again, if you ask Andreessen Horowitz. The venture firm just led a $15 million funding round for Firespotter Labs (creators of the audio conferencing tool UberConference and the mobile rating app Jotly), with participation from Google Ventures.

“Andreessen Horowitz has a wealth of knowledge and an impressive track record in advising industry-leading start-ups such as Skype, GitHub, Box, and Facebook,” said Firespotter CEO and co-founder Craig Walker in a statement. “We are thrilled that [Blake Krikorian, co-founder and former CEO of Sling Media], one of the tech industry’s most savvy executives, will join our board and help direct the course of telephony products such as UberConference.”

If you haven’t seen UberConference in action, you’ll want to check out this video.  A winner at TechCrunch Disrupt 2012, the audio conferencing tool is especially useful for conferences where the callers might be meeting each other for the first time. It has a visual interface that shows who in the group is currently speaking.

Google+ Hangouts has a similar feature for its video conferencing service, but this one you can use without having to dress nicely or fix your hair. Not surprisingly, Google purchased Walker’s previous venture, GrandCentral, in July 2007, which later became Google Voice. The serial entrepreneur had also sold Dialpad Communications to Yahoo! in 2005, which became Yahoo! Voice.

Firespotter Labs raised $3 million from Google Venture in 2011. With this latest round of funding, Firespotter will expand its engineering team and create new products.