Phonon

Phonon is the speech recognition engine from Fermion Research. It runs the Phonon models on Apple silicon through MLX, on CPUs under Linux (x86-64 and Arm), Windows and macOS (Apple silicon and Intel Macs), and on NVIDIA GPUs through the CUDA image. It transcribes files from the command line, transcribes the microphone live, and serves an OpenAI-compatible endpoint. Phonon-2.5 (156 MB download) transcribes 25 languages, Phonon-2.5 English (158 MB) and Phonon-2 (158 MB) are the English models, and Phonon-1 (415 MB), Phonon-1 Big (581 MB) and Phonon-1 Micro (285 MB) also run.

Models

Model	Download	Weights
Phonon-2.5 (phonon-2.5), 25 languages	156 MB	huggingface.co/FermionResearch/Phonon-2.5
Phonon-2.5 English (phonon-2.5-en)	158 MB	huggingface.co/FermionResearch/Phonon-2.5-English
Phonon-2 (phonon-2)	158 MB	huggingface.co/FermionResearch/Phonon-2
Phonon-1 (phonon-1)	415 MB	huggingface.co/FermionResearch/Phonon-1
Phonon-1 Micro (phonon-1-micro)	285 MB	huggingface.co/FermionResearch/Phonon-1-Micro
Phonon-1 Big (phonon-1-big)	581 MB	huggingface.co/FermionResearch/Phonon-1-Big

Phonon-2 for Core ML (Neural Engine): huggingface.co/FermionResearch/Phonon-2-CoreML · github.com/fermionresearch/phonon-coreml

Accuracy and speed for each model are on its model page (fermionresearch.com/models/phonon-2 and the model cards above).

Install

Python 3.10 or newer (macOS's built-in python3 is 3.9). On a Mac, create a virtual environment with a newer Python first:

python3.12 -m venv .venv && source .venv/bin/activate
pip install fermion-research

Apple silicon (MLX engine)

pip install "fermion-research[mlx]"

Linux, Windows and Intel Mac CPUs. pip install fermion-research is the whole setup. On Linux, install torch from its CPU wheel index first, which skips the GPU build. Intel Macs: CPU engine (Python 3.10 to 3.12).

pip install --no-deps torch --index-url https://download.pytorch.org/whl/cpu   # Linux only
pip install fermion-research

Supported CPUs: x86-64 with SSE4.1 or newer and 64-bit Arm with NEON. AVX2, AVX-512 VNNI and AMX processors, and dotprod and i8mm Arm processors, run faster tiers of the same kernels; processors without them run a slower baseline tier with the same transcripts. fermion describe shows the features found on your machine and the tier it runs; docs/cpu.md has the detail.

CPU container (amd64 and arm64)

docker run --rm -v "$PWD":/audio -v phonon-cache:/home/phonon/.cache ghcr.io/fermionresearch/phonon-cpu:2.0.12 transcribe phonon-2.5 /audio/recording.wav

NVIDIA CUDA container

docker run --rm --gpus all -v "$PWD":/audio -v phonon-cache:/home/phonon/.cache ghcr.io/fermionresearch/phonon-cuda:1.0.11 transcribe phonon-2.5 /audio/recording.wav

Run

phonon runs Phonon-2, phonon-1 runs Phonon-1, and fermion <command> <model> runs any model by name. Name the model. Phonon never guesses.

phonon transcribe meeting.wav               # transcribe a file with Phonon-2
phonon transcribe meeting.wav --json        # the same, as JSON with word timestamps
phonon transcribe meeting.wav --hotwords "Ada, Quillon"    # favour names and terms
phonon listen                               # live microphone transcription (Apple silicon)
phonon serve                                # OpenAI-compatible HTTP server on 127.0.0.1:8000
fermion transcribe phonon-2 meeting.wav     # the same, naming the model
fermion transcribe phonon-2.5 reunion.wav   # Phonon-2.5: 25 languages, detected from the audio
fermion transcribe phonon-2.5-en call.wav   # Phonon-2.5 English

curl -s http://127.0.0.1:8000/v1/audio/transcriptions \
  -F "[email protected]" \
  -F "model=phonon-2"

Streaming

phonon serve also transcribes live audio over a WebSocket at /v1/audio/stream. The protocol and a reference client are in docs/server.md.

Dictation tools

A dictation tool keeps one Phonon server running and sends each recording to it, over a local port or an owner-only Unix socket.

fermion serve phonon-2 --port 8010 --threads 4         # or: phonon serve --port 8010
fermion serve phonon-2 --unix-socket ~/.cache/fermion/phonon.sock   # owner-only socket in place of an API key

engine = "whisper"
[whisper]
backend = "remote"
remote_endpoint = "http://127.0.0.1:8010"
remote_model = "phonon-2"

Keeping the server running at login is covered in docs/server.md.

fermion models lists every model with its aliases and marks the ones already on the machine.

Documentation

• docs/cli.md, the command line.
• docs/server.md, the HTTP server and its API.
• docs/hotwords.md, favouring names and terms (hotwords).
• docs/install.md, installation on every platform.
• docs/cpu.md, running on CPUs, no GPU required.
• docs/cuda.md, the NVIDIA CUDA image.
• docs/troubleshooting.md, fixes for common problems.

The CUDA image is built from docker-phonon2/ and the CPU image from docker-cpu-phonon2/.

Licence

The Phonon-2.5, Phonon-2.5 English and Phonon-2 weights are released under CC-BY-4.0. They are a derivative of NVIDIA's parakeet-tdt-0.6b-v3, with the changes listed in the NOTICE file of the weights repository. The Phonon-1 family weights and the command line are released under Apache-2.0, and Phonon-1 is built on Qwen/Qwen3-ASR-0.6B, also under Apache-2.0. See LICENSE and NOTICE.