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The Humanness Index™
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The Humanness Index™

The open benchmark for how human voice AI sounds. Built and operated by Vapi.

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Code is Apache-2.0. Standings data is CC BY 4.0. Audio clips and source voices are licensed recordings, all rights reserved. Provider logomarks belong to their respective owners and are used nominatively. “The Humanness Index™” name and logo are Vapi trademarks; see TRADEMARKS.md.

  1. Humanness Index™
  2. Neuphonic
  3. neu_hq

Humanness Index™ · TTS model

Neuphonic

neu_hq

by Neuphonic

neu_hq is the quality tier of Neuphonic's text to speech line and the model name its SDKs and integrations carry by default.

Rank
#13
Humanness
63
Likely rank
#1–20
Blind votes
2

Standings as of Jun 13, 2026, 01:14 UTC

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A real arena clip: a cloned source voice reading a customer support prompt at phone quality.

neu_hq key stats

Latency (measured)
276 ms1
Languages
92
Streaming
Yes3
Voice cloning
instant, ~6 s sample4
Released
August 20255
  1. Vapi streaming benchmark (50 trials per model) (checked 2026-06-11) Median of 50 sequential live streaming trials, June 2026; includes network RTT from the benchmark machine.
  2. docs.neuphonic.com/build-group/languages (checked 2026-06-12) English, Chinese, French, German, Japanese, Korean, Spanish, Portuguese, and Urdu.
  3. docs.neuphonic.com/build-group/text-to-speech (checked 2026-06-12) SSE and WebSocket streaming surfaces.
  4. docs.neuphonic.com/build-group/voice-cloning (checked 2026-06-12) Docs ask for a 6 second or longer clean sample; in practice the clone endpoint accepts roughly 3-10 s clips.
  5. docs.neuphonic.com/changelog (checked 2026-06-12, confidence: medium) Neuphonic published no model-specific date; its changelog marks API v1.0.0 in August 2025. The neu_hq name predates GA (the closed beta opened in late 2024).

Background

neu_hq is the quality tier of Neuphonic's text to speech line and the model name its SDKs and integrations carry by default. Neuphonic, a London startup founded in 2024, pairs the hosted API with an open source on-device family (NeuTTS), and the hosted service streams over SSE and WebSockets across nine languages with instant voice cloning.

Sources: docs.neuphonic.com, github.com

At a glance

Neuphonic's public API currently serves a single voice pool and does not expose model selection, so this entry represents that served system under its neu_hq branding. The historical neu_fast realtime sibling is not listed separately: with one pool behind the API, a second row would test the same model twice. In our 50 trial streaming benchmark it returned first audio in a median of 276 ms including network time.

Sources: docs.neuphonic.com

Position in the rankings

Standings as of Jun 13, 2026, 01:14 UTC

RankProviderModelHumannessLatency
#11InworldInworldTTS-1.5-max65337 ms
#12ElevenLabsElevenLabsTurbo v264302 ms
#13NeuphonicNeuphonicneu_hq63276 ms
#14Smallest.aiSmallest.aiLightning v3.162420 ms
#15MiniMaxMiniMaxSpeech 2 HD62357 ms

See the full Humanness Index™ rankings

Frequently asked questions

How is neu_hq tested on the Humanness Index™?
Listeners hear neu_hq against another model in a blind head to head round, both voices reading the same customer support prompt from the same cloned source voice, and they pick whichever sounds more human. Its Humanness score derives purely from those votes.
Why is neu_fast not on the Index?
Neuphonic historically exposed neu_fast as the realtime sibling of neu_hq, but the current public API does not expose model selection and serves one voice pool. The Index lists that pool once, under the neu_hq name; a separate neu_fast entry would put two names on the same system.

Keep exploring

NeuphonicNeuphonicAll Neuphonic models on the Index

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