Sonic: 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.

  • American EnglishSkylar - American English
  • Canadian FrenchSkylar - Canadian French
  • Castilian SpanishSkylar - Castilian Spanish

Custom Pronunciation Dictionaries

Specify custom pronunciations for proper nouns, domain terms, and anything else that needs to sound exactly right.

  • WordPronunciation
  • charcuterieshar-koo-terie
  • subpoena<<s|ə|ˈ|p|i|n|ə>>
  • epinephrine<<ˌ|ɛ|p|ɪ|ˈ|n|ɛ|f|ɹ|ɪ|n>>

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.

Fluent and native, worldwide

Reach international markets with Sonic — 40+ languages and a wide range of accents, all with native-speaker quality voices.

Most popular locales

Enterprise-grade security. From Cloud to Local.

  • HIPAA compliant

  • SOC 2 Type 2

  • GDPR

  • PCI

Trusted by leading enterprises. Speaking from experience.

Discover success stories

Elise AI

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 tour conversion and a 12.2% increase in customer engagement.

ServiceNow

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.

Sierra

Cartesia Sonic 3.5 has become one of the top-performing models for us by combining low latency with natural pacing… helping us deliver strong voice quality across a growing set of languages where other models often fall short.

Callers

Sonic 3.5 has been a meaningful upgrade for Callers… latency and naturalness directly impact conversational flow and user success, and the new model noticeably improves both. We've seen more human interactions — especially in high-volume customer conversations where every millisecond and every turn matters.

Take2 AI

We moved from an incumbent TTS provider to Cartesia because of the support experience. After repeated roadblocks with our previous provider, the difference with Cartesia has been transformative — responsive, technical, and genuinely invested in our success.

Cresta

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.

Bolna

Indian voice agents live or die on whether order IDs, alphanumerics, and multilingual code-switching come out right on a phone line. Sonic 3.5 handles alphanumerics natively… and lands first audio at 100ms p90.

Goodcall

Sonic is the only product in existence with model latency of less than 100 ms, outperforming its next best alternative by a factor of four. This level of performance represents a quantum leap forward.

Quora

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.

Fundamento

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.

FAQs

What makes Cartesia the best realtime TTS compared to other TTS models?
Can Cartesia run on-prem or in my own cloud (VPC)?
How does Cartesia handle data privacy, compliance, and security?
Can I create voices with Cartesia?
What do Cartesia's plans cost, and what's included?
When should I contact Sales?

Frontier research, deployed in every conversation.