# Gradium open-sources Phonon 31M on-device TTS model under Apache 2.0

Digest AI · Generative AI & Models · published 2026-10-22T16:56:12Z

Canonical: https://digestai.news/story/gradium-open-sources-phonon-31m-on-device-tts-model-under-apache-2-0

## Summary

Gradium, a Paris voice AI company spun out of Kyutai, has open‑sourced its Phonon family of on‑device text‑to‑speech models. The English‑only Phonon 31m model contains 31 M parameters, is packaged in a 64.5 MB q8 GGUF file and is released under the Apache 2.0 license. A larger 40 M‑parameter version (74.6 MB) and a multilingual 40 M model covering five languages are offered under a CC BY‑NC 4.0 license. Gradium reports that Phonon 31m achieves 1.70 % word‑error rate on a 500‑sentence hard set, compared with 3.50 % for the Kokoro baseline, and 0.51 % LLM‑WER on a easier Seed‑TTS set.

It runs on CPUs, phones, Raspberry Pi 5, browsers via WASM/WebGPU and NVIDIA GPUs, with no GPU required for inference. The runtime is available under MIT or Apache‑2.0 and supports Rust, Python, Swift, C/C++ and browser bindings, plus an OpenAI‑compatible server and WebSocket interface.

## Key points

- Phonon 31m has 31M parameters, 64.5 MB file, 1.70% WER on hard set vs 3.50% for Kokoro
- Runs on CPUs, phones, Raspberry Pi 5, browsers (WASM, WebGPU) and NVIDIA GPUs; Apache 2.0 license

## Why it matters

On‑device TTS removes cloud latency and per‑character costs, enabling fast, private speech generation on edge devices and expanding privacy‑preserving AI applications.

## Sources

1. [Gradium Open-Sources Phonon, a 31M-Parameter On-Device TTS Model Under Apache 2.0](https://marktechpost.com/2026/10/22/gradium-phonon-31m-on-device-tts) (MarkTechPost, 2026-10-22)

## Cite

Digest AI, "Gradium open-sources Phonon 31M on-device TTS model under Apache 2.0", 22 October 2026, https://digestai.news/story/gradium-open-sources-phonon-31m-on-device-tts-model-under-apache-2-0

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