July 20, 2026
Rime Raises $24 Million as Its Human-Sounding Voices Keep Callers From Hanging Up
A voice AI company that trains its models on real conversations rather than audiobooks has closed a $24 million Series A, arguing that how a machine speaks can decide whether a customer stays on a call.
That company is Rime, whose Series A was led by M13, with participation from Twilio Ventures, Corazon Capital, and existing backer Unusual Ventures. Rime said the money will fund its proprietary conversational speech dataset and new hires across engineering and research.
A Linguistics-First Approach to Synthetic Speech
Many voice AI companies chase a general sense of naturalness while Rime takes a different route, building its models around academic speech science. The company was founded in 2022 by Lily Clifford, a Stanford linguistics PhD student who left the programme to work on speech synthesis; Brooke Larson, a PhD linguist and former Amazon Alexa engineer; and Ares Geovanos, a Stanford-trained engineer.
Rather than scraping audio from the web, Rime records its own conversations in a San Francisco studio and uses that data to train phoneme-based models. The method is designed to get pronunciation right for tricky industry terms and brand names without asking each customer to retrain a model.
Clifford said the hardest parts of conversation are also the hardest to measure, adding that there is “no unit test for sounding like you care.” She described voice interaction as a design problem as much as an engineering one, and said the new funding would let Rime multiply its investment in data.
Traction in Healthcare and Finance
Rime’s technology now handles close to 100 million phone calls a month for names including Mayo Clinic, Dialpad, Upstart, and Asurion. The company has found particular traction in healthcare and financial services, where getting complex terminology right and meeting compliance rules such as HIPAA are non-negotiable.
Upstart said accuracy is a requirement for customer trust in financial services, and Rime lets the lender build experiences that serve its customers’ needs.
According to an independent study by Miravoice, which compared 12 voices from three vendors across 100,000 calls, Rime’s voices had lower early hang-up rates and the fastest median call completion time of any provider tested.
Why Voice is Heating Up Again
The round arrives as voice returns to the centre of customer service conversations. After years of frustrating menu trees and robotic prompts, vendors are racing to make automated calls sound human as conversational AI redefines voice technology for the digital age.
Others are chasing the same prize from different angles. Sinch has been working to close the divide between text-based AI and live phone calls, more proof that voice is back and AI is getting real. And as more brands add automated agents, the teams that win are the ones that follow voice bot best practices and get the fundamentals right.
Alongside the raise, Rime appointed Rafael Valle, formerly head of audio research at Meta’s Super Intelligence Lab, as chief science officer. Blumberg, the incoming board member, said the design patterns that will define the speech-to-speech era have not been built yet, and credited Rime’s founders with a rare combination of AI research and linguistic depth.
