SAN FRANCISCO — Rime, an enterprise voice AI platform, has reeled in $24 million in Series A funding led by M13, with participation from Twilio Ventures, Corazon Capital, and continued participation from Unusual Ventures and other existing investors. Morgan Blumberg, Partner at M13, will join Rime’s Board of Directors. The funds will be used to invest in Rime’s proprietary conversational dataset and make strategic hires in engineering and research as the company scales its infrastructure.
Rime also announced the appointment of Rafael Valle as Chief Science Officer. Valle, who previously led audio research at Meta’s Super Intelligence Lab, joins Rime to accelerate the company’s research and product innovation.
Voice is the last interface computers are still bad at. While many voice AI companies chase generic signals of naturalness, Rime takes a linguistics-first approach. Founded by Lily Clifford (while pursuing a Stanford linguistics PhD), Brooke Larson (PhD linguist, ex-Amazon Alexa), and Ares Geovanis (Stanford engineer), Rime blends academic speech science with one of the world’s largest collections of expressive multilingual conversational speech. The bet is that the company defining this next interface won’t be the one with the biggest model, it will be the one that can measure what good actually sounds like, and design toward it.
“The things that matter most in conversation are the hardest to pin down. Response relevance is hard to specify; speech appropriateness is hard to verify. There’s no unit test for sounding like you care,” said Lily Clifford, co-founder and CEO of Rime. “That’s exactly why this is a design problem, not just an engineering one. We’re building voice interaction models, systems where our linguistic judgment and taste become research instruments, not afterthoughts. With this new funding and Rafael Valle joining as Chief Science Officer, we’re 10x-ing our data investment to define the design language of conversational general intelligence.”
Today, Rime powers nearly 100 million phone calls monthly for companies like Mayo Clinic, Dialpad, Upstart, and Asurion. By staying focused strictly on the modeling layer and their linguistics roots, the platform has gained significant traction in healthcare and financial services, where pronunciation accuracy for complex terminology and HIPAA compliance are critical.
“In financial services, the stakes for voice AI are exceptionally high and accuracy is a requirement for customer trust,” said Shiv Indap, Upstart. “Rime’s ability to handle complex financial use cases with precision allows us to build experiences that truly serve our customer’s needs.”
The efficacy of Rime’s approach was recently validated by an independent study conducted by Miravoice, which evaluated 12 voices from three vendors, across 100,000 calls, finding that Rime’s voices resulted in statistically significantly lower “Hung Up During Intro” (HUDI) rates compared to major competitors. Rime also demonstrated the fastest median time to completion among all providers tested, proving that linguistic nuances like cadence and speed drive measurable business results. Rime voices keep more customers on the line longer.
“The design patterns that will define the speech-to-speech era of AI haven’t been built yet. Rime is doing the foundational work by combining frontier AI with deep linguistic expertise to create the speech infrastructure the next generation of AI products will rely on,” said Morgan Blumberg, Partner at M13. “Lily, Ares and Brooke are building Rime with the rare combination of world-class AI research and deep linguistic expertise to deploy real time voice people can trust in complex, regulated environments.”
