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.

References¶

[1]	Sohn, N. S. Kim, and W. Sung, “A statistical model-based voice activity detection,” Signal Processing Letters, vol. 6, no. 1, pp. 1-3, January 1999.