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VoiceFilter : Targeted Voice Separation Model

This is an introduction to「VoiceFilter」, a machine learning model that can be used with ailia SDK. You can easily use this model to create AI applications using ailia SDK as well as many other ready-to-use ailia MODELS.


VoiceFilter is a speech separation model developed by Google AI and released in May 2020. It is capable of extracting the voice of an designated person from an audio file in which multiple people are speaking at the same time.


Although the performance of speech recognition has increased in recent years, the accuracy in environments where multiple people are talking is not sufficient. To solve this problem, it is important to improve the recognition by using speech separation to extract the voices from different speakers. However, it is a complex problem to know how many people are currently speaking. Also, speakers need to be labeled, which requires the use of deep clustering or deep attractor network.

The proposed method in this model treats all voices other than the target speaker (whose voice we want to extract) as noise. In addition, it is assumed that a sample of the voice of the target speaker is provided for reference. This method is similar to the traditional task of speech separation, but it is targeted to a designated individual. This speaker-dependent speech separation task is often referred to as as voice filtering.

In the VoiceFilter architecture, two types of models are used: a speaker recognition network that produces speaker-discriminative embeddings (aka d-vectors), and a spectrogram masking network which extracts a specific person’s voice from a noisy spectrogram of several people talking and the target speaker embeddings as input.


The speaker recognition network computes speaker embedding d-vectors based on a 3-layer LSTM. It takes as input a spectrogram extracted from windows of 1600 ms, and outputs speaker embeddings with a fixed dimension of 256. A d-vector is computed by sliding windows with 50% overlap, and averaging the L2-normalized d-vectors obtained on each window.

The VoiceFilter system calculates a magnitude spectrogram from “noisy audio” (recording with mixed voices of multiple people). This magnitude spectrogram is then multiplied with a soft mask produced from the d-vector, and merged with the phase of the noisy audio. The result is then processed by applying an inverse STFT to obtain the output waveform.

Word Error Rate (WER) was used to evaluate the model accuracy on the LibriSpeech and VCTK datasets. The speech recognizer used for the WER evaluation was trained on a YouTube dataset.

In the tables below, Clean WER refers to WER for clean audio, and Noisy WER refers to WER for noisy audio. Using VoiceFilter, the error rate for noisy audio is reduced from 55.9% to 23.4%.



You can use VoiceFilter with ailia SDK using the following command. mixed.wav refers to the the audio of several people talking, and ref-voice.wav is the reference sample of the voice of the target speaker.

$ python3 --input mixed.wav --reference_file ref-voice.wav

ax Inc. has developed ailia SDK, which enables cross-platform, GPU-based rapid inference.

ax Inc. provides a wide range of services from consulting and model creation, to the development of AI-based applications and SDKs. Feel free to contact us for any inquiry.



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