StationaryNoiseEstimation

This block calculates a stationary noise estimate.

The input data should be 1-D frames representing the estimate signal spectra. It is assumed that the first few frames of data contain only noise and these frames are used to form the noise estimate. The number of initial frames to employ can be set using the parameter NFRAMES.

The noise estimate is formed from the average of the initial frames and is sent to out1.

If IGNORE_LARGE is set then the values in the first NFRAMES are sorted and the larger 50% are discarded before calculating the average. (This feature may be useful for getting a crude estimate of the noise floor for signals that are not entirely stationary).

A clean signal spectrum estimate is calculated by subtracting the noise estimate from the noisy input signal. This is sent to out2. It should be noted that because the noise may be overestimated, the clean signal estimate may have negative values, even when working in the power spectral domain.

The input signal variance is estimated over the initial NFRAMES and is sent to out3.

Inputs	Meaning	Sample	1-D frame	2-D frame
in1	noisy spectral data	Yes	Yes	Yes

Outputs	Meaning
out1	stationary noise spectrum estimate
out2	signal spectrum estimate
out3	noise variance estimate

Parameters	Type	Default	Meaning
NFRAMES	Integer	-	Number of initial frames to use for forming noise estimate
IGNORE_LARGE	Boolean	False	Ignore larger values when making initial estimate