Humanness Index™ · TTS model
by Cartesia
Sonic 3.5 is Cartesia's current flagship, released in May 2026.
Standings as of Jun 13, 2026, 00:15 UTC
A real arena clip: a cloned source voice reading a customer support prompt at phone quality.
Sonic 3.5 is Cartesia's current flagship, released in May 2026. Cartesia positions it as its most natural and fastest model, with sub 90 ms latency and native support for 42 languages. It is tuned for production agent transcripts: it reads order numbers, emails, and confirmation codes correctly without preprocessing, and it resolves heteronyms like read and bow from the surrounding words.
Sources: docs.cartesia.ai
Alphanumerics and heteronyms without preprocessing, 42 languages, and a published sub 90 ms latency claim. In our 50 trial streaming benchmark it returned first audio in a median of 128 ms, the fastest measured time among current generation models on the Index.
Sources: docs.cartesia.ai
Standings as of Jun 13, 2026, 00:15 UTC
| Rank | Provider | Model | Humanness | Latency |
|---|---|---|---|---|
| #1 | xAI | Grok TTS | 100 | 460 ms |
| #2 | xAI | Grok TTS (Streaming) | 98 | 285 ms |
| #3 | Cartesia | Sonic 3.5 | 82 | 128 ms |
| #4 | Canopy Labs | Orpheus | 78 | — |
| #5 | ElevenLabs | Eleven v3 | 76 | 758 ms |
The benchmark is open source. Suggest a model, read the methodology, or ask us to put your voice in the arena.
