Humanness Index™ · TTS model
by Cartesia
Sonic 3.5 is the May 2026 Sonic snapshot, and was Cartesia's flagship until Sonic 3.6 shipped in August 2026.
Standings as of Oct 26, 2026, 16:41 UTC
A real arena clip: a cloned source voice reading a customer support prompt at phone quality.
Sonic 3.5 is the May 2026 Sonic snapshot, and was Cartesia's flagship until Sonic 3.6 shipped in August 2026. Cartesia positioned it as its most natural and fastest model at release, 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 including network time from the benchmark machine.
Sources: docs.cartesia.ai
Standings as of Oct 26, 2026, 16:41 UTC
| Rank | Provider | Model | Humanness | Latency |
|---|---|---|---|---|
| #12 | Cartesia | Sonic 3.6 | 71 | 101 ms |
| #13 | Inworld | TTS-2 | 71 | 288 ms |
| #14 | Cartesia | Sonic 3.5 | 71 | 128 ms |
| #15 | MiniMax | Speech 2 Turbo | 71 | 315 ms |
| #16 | ElevenLabs | Flash v2.5 | 69 | 197 ms |
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