VoiceActivityDetection Node¶
Outline of the node¶
This node delimits the a speech-present period.
Typical connection¶
This node is connected with the VoiceActivityDetection node. Typical connection of this node is depicted as follows:
Input-output and property of the node¶
Input¶
- AUDIO_SPECTRUM Matrixd<complex<float> >
- Windowed spectrum data. A row index is channel, and a column index is frequency.
Output¶
- VAD_DECISION Vector<ObjectRef>
- Decision of speech-present frame
Parameters¶
Parameters of this node are listed as follows:
| Parameter name | Type | Default value | Unit | Description |
|---|---|---|---|---|
| VAD_NOISE_DURATION | float | 3.0 | second | Time duration to be regarded as “noise” from the first frame |
| VAD_THRESHOLD | float | 50.0 | Threshold for voice activity decision. | |
| ADVANCE | int | 160 | sample | The length in sample between a frame and a previous frame. |
| SAMPLING_RATE | int | 16000 | Hz | Sampling rate. |
Detail of the node¶
This node estimates the voice activity by using log likelifood ratio of speech and noise variances of the zero-mean Gaussian statistical model [1]. Let \(X_{l/r}\left[f, n\right]\) be an input audio signal at frequency bin \(f\) and time frame \(n\), this method regards speech-present when following equation is satisfied:
\(\frac{1}{F} \sum^{F}_{f=1} \gamma \left[f,n\right]- {\rm log} \gamma \left[f,n\right] -1 > \eta_{VAD}\),
\(\lambda_N \left[f\right] = E\left|N_l\left[f\right] \cdot N_r\left[f\right]^{\ast}\right|\),
\(\gamma\left[f,n\right]=\left|X_l \left[f,n\right] \cdot X_r\left[f,n\right]^{\ast}\right|/ \lambda_N\left[f\right]\),
where \(N\left[f\right]\) and \(\eta_{VAD}\) represent the variance of a estimated noise and threshold parameter, respectively.