Calls the algorithm of Lamel et al, 1981. IMPORTANT: The passed signal envelope values are absolute amplitude values derived from the framed waveform. These are converted to decibels before passing to the LAMEL method. NOTE: The returned background noise value ignores the SD part of the Gaussian noise model.

Declaration

public static double CalculateBackgroundNoise(double[] signalEnvelope)

Parameters

Type	Name	Description
Double[]	signalEnvelope	Amplitude values.

Returns

Type	Description
Double	Modal noise value in decibels.

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CalculateNoiseUsingLamelsAlgorithm(Double[], out Double, out Double, out Double, out Double)

Implements the "Adaptive Level Equalisatsion" algorithm of Lamel et al, 1981 - with modifications for our signals. Units are assumed to be decibels. Returns the min and max frame dB AND the estimate MODAL or BACKGROUND noise for the signal array IF This modal noise is subtracted from each frame dB, the effect is to set set average background noise level = 0 dB. The algorithm is described in Lamel et al, 1981. USED TO SEGMENT A RECORDING INTO SILENCE AND VOCALISATION NOTE: noiseThreshold is passed as decibels. Original Lamel algorithm ONLY SEARCHES in range min to 10dB above min.

This method debugged on 7 Aug 2018 using following command line arguments: audio2csv Y:\TheNatureConservency\Myanmar\20180517\site112\2018_02_14_Bar5\20180214_Bar5\20180214_101121_Bar5.wav Towsey.Acoustic.yml C:\Temp... -m True.

Declaration

public static void CalculateNoiseUsingLamelsAlgorithm(double[] dBarray, out double minDb, out double maxDb, out double modeNoise, out double sdNoise)

Parameters

Type	Name	Description
Double[]	dBarray	signal in decibel values.
Double	minDb	minimum value in the passed array of decibel values.
Double	maxDb	maximum value in the passed array of decibel values.
Double	modeNoise	modal or background noise in decibels.
Double	sdNoise	estimated sd of the noies - assuming noise to be guassian.

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ModalNoiseRemovalAndGetSonograms(Double[,], TimeSpan, TimeSpan, Int32, Int32)

This method produces four spectrograms using four different values of neighbour hood decibel threshold. It can be used for test purposes.

Declaration

public static Image ModalNoiseRemovalAndGetSonograms(double[, ] deciBelSpectrogram, TimeSpan xAxisInterval, TimeSpan stepDuration, int nyquist, int hzInterval)

Parameters

Type	Name	Description
Double[,]	deciBelSpectrogram	the noisy decibel spectrogram.
TimeSpan	xAxisInterval	x-axis tic interval.
TimeSpan	stepDuration	the x-axis times scale.
Int32	nyquist	max freq value.
Int32	hzInterval	y-axis frequency scale.

Returns

Type	Description
SixLabors.ImageSharp.Image	Image containing four sepctrograms.