Sonic-3.5
The fastest and most natural text to speech model
Ranked #1 for naturalness, sub-90ms latency, and natively multilingual across 40+ languages.
Sonic features built for your voice
Clone your voice, localize it into 42 languages, and fine-tune every word.
Voice cloning
Clone any voice instantly with 10 seconds of audio. High speaker similarity means the brand voice you love stays true, even at scale.
Localization
Localize any audio clip with native-speaker quality. Emotion, tone, and speaker identity carry through — nothing gets lost in translation.
Custom Pronunciation
Specify custom pronunciations for proper nouns, domain terms, and anything else that needs to sound exactly right.
One voice model for your entire business.
See how enterprise teams use Sonic across every use case — and hear it for yourself.
Marketing
Calls warm leads the day a campaign fires, personalizes the opener, and books meetings in the CRM.
Sales
Calls signups within seconds, qualifies them, and books a meeting before the prospect checks their phone.
Customer support
Authenticates callers, pulls live account data, and resolves billing questions, order status, and account issues without hold times or transfers.
Training & Dev
Spins up a realistic prospect persona that reps can practice live sales calls against, handling objections, pushback, and curveballs on demand.
Recruiting
Calls applicants instantly, screens them, and pushes a qualification summary to the ATS before the call ends.
Customer success
Calls customers at key lifecycle moments — onboarding check-ins, renewal reminders, post-support follow-ups.
Fluent and native, worldwide
Reach international markets with Sonic — 40+ languages and a wide range of accents, all with native-speaker quality voices.
Enterprise-grade security. From Cloud to Local.
Trusted by leading enterprises. Speaking from experience.
"We didn't switch to Sonic 3.5 because it was incrementally better, we switched because nothing else came close… we've seen a 2.9% lift in our conversion and a 12.2% increase in customer engagement."
— Elise AI
"Cartesia's state-space models bring enterprise-grade speed and quality to our AI Voice Agents… making it possible for businesses to deploy secure, scalable voice agents that can understand, act, and adapt in real time."
— ServiceNow
"Sonic is the only product in existence with model latency of less than 100ms, outperforming its next best alternative by a factor of four. This level of performance represents a quantum leap forward."
— Goodcall
"We run 20M+ outbound calls per month on Cartesia, with peak concurrency of 5,000 calls in a single minute, and 100ms time-to-first-byte — 2x faster than every other voice provider we tested."
— Fundamento
"Sonic powers audio on Poe across 100+ voices and 14 languages, supporting Quora's millions of users with SOC 2 compliance and unlimited concurrency for enterprise customers."
— Quora
"Sonic 3.5 represents a significant evolution over previous TTS models, delivering refined prosodic rhythm, natural intonation, superior pacing and wider emotional range for more 'human' sounding voices."
— Cresta