I'm looking for a library in python that has fairly accurate speech recognition. It would preferably return a string indicating what was said, so that I can work with the string to do other things. Thanks!!!

I looked at this related question, but I don't think we're asking the same thing.


2 Answers 2


You can use CMU Sphinx:

  • free and open source
  • recognizer library written in C but provides Python bindings
  • often mentioned as one of the best open source speech recognition engines

When looking for a speech recognition software for Linux a while ago, I was told that CMU Sphinx' accuracy is significantly lower than Dragon (I'd be curious if anyone here has a benchmark Sphinx vs Dragon). However, if your voice recordings are in a well restricted domain, you might be able to train CMU Sphinx well enough.


OpenAI's Whisper (off-line, MIT license, Python 3.9, CLI) yields some highly accurate transcription. To use (tested on Ubuntu 20.04 x64 LTS):

conda create -y --name whisperpy39 python==3.9
conda activate whisperpy39
pip install git+https://github.com/openai/whisper.git 
sudo apt update && sudo apt install ffmpeg
whisper recording.wav
whisper recording.wav --model large

If using an Nvidia 3090 GPU, add the following after conda activate whisperpy39

pip install -f https://download.pytorch.org/whl/torch_stable.html
conda install pytorch==1.10.1 torchvision torchaudio cudatoolkit=11.0 -c pytorch

it can be used as a Python lib, e.g.:

import whisper

model = whisper.load_model("base")

# load audio and pad/trim it to fit 30 seconds
audio = whisper.load_audio("audio.mp3")
audio = whisper.pad_or_trim(audio)

# make log-Mel spectrogram and move to the same device as the model
mel = whisper.log_mel_spectrogram(audio).to(model.device)

# detect the spoken language
_, probs = model.detect_language(mel)
print(f"Detected language: {max(probs, key=probs.get)}")

# decode the audio
options = whisper.DecodingOptions()
result = whisper.decode(model, mel, options)

# print the recognized text

Performance info below.

Model inference time:

Size Parameters English-only model Multilingual model Required VRAM Relative speed
tiny 39 M tiny.en tiny ~1 GB ~32x
base 74 M base.en base ~1 GB ~16x
small 244 M small.en small ~2 GB ~6x
medium 769 M medium.en medium ~5 GB ~2x
large 1550 M N/A large ~10 GB 1x

WER on several corpus from https://cdn.openai.com/papers/whisper.pdf:

enter image description here

WER on several languages from https://github.com/openai/whisper/blob/main/language-breakdown.svg:

enter image description here

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