Class DspFilters

digital signal processing FILTERS methods.

Inheritance
Object
DspFilters
Inherited Members
Namespace: AudioAnalysisTools.DSP
Assembly: AudioAnalysisTools.dll
Syntax
public static class DspFilters

Fields

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Pi

Declaration
public const double Pi = 3.1415926535897931
Field Value
Type Description
Double

Methods

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AmplifyAndClip(Double[], Double)

This is ultracrude device but ................

Declaration
public static double[] AmplifyAndClip(double[] signal, double amplifificationFactor)
Parameters
Type Name Description
Double[] signal
Double amplifificationFactor
Returns
Type Description
Double[]
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DisplaySignal(Double[])

Declaration
public static void DisplaySignal(double[] sig)
Parameters
Type Name Description
Double[] sig
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DisplaySignal(Double[], Boolean)

Declaration
public static void DisplaySignal(double[] sig, bool showIndex)
Parameters
Type Name Description
Double[] sig
Boolean showIndex
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Filter_DecayingSinusoid(Double[], Double, Double, Double, Double)

converts passed arguments into step decay and step radians ie radians per sample or OMEGA.

Declaration
public static double[] Filter_DecayingSinusoid(double[] signal, double sf, double tHalf, double period, double filterDuration)
Parameters
Type Name Description
Double[] signal

the signal.
Double sf

sampling frequency.
Double tHalf

half life in seconds.
Double period

of the cycle of interest.
Double filterDuration

length of filter in seconds.
Returns
Type Description
Double[]
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Filter_DecayingSinusoid(Double[], Double, Double, Int32)

Declaration
public static double[] Filter_DecayingSinusoid(double[] signal, double stepDecay, double stepRadians, int filterLength)
Parameters
Type Name Description
Double[] signal
Double stepDecay
Double stepRadians
Int32 filterLength
Returns
Type Description
Double[]
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FIR_Filter(Double[], Double[])

A "finite impulse response" (FIR) filter uses only the input signals, while an "infinite impulse response" filter (IIR) uses both the input signal and previous samples of the output signal.

FIR filters are always stable, while IIR filters may be unstable. This filter is linear, causal and time-invariant.

Declaration
public static double[] FIR_Filter(double[] signal, double[] filterCoeff)
Parameters
Type Name Description
Double[] signal

input signal.
Double[] filterCoeff

filter coefficients.
Returns
Type Description
Double[]

the filtered signal.
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GenerateTestRecording(Int32, Double, Int32[], WaveType)

Declaration
public static AudioRecording GenerateTestRecording(int sampleRate, double duration, int[] harmonics, WaveType waveType)
Parameters
Type Name Description
Int32 sampleRate
Double duration
Int32[] harmonics
WaveType waveType
Returns
Type Description
AudioRecording
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GenerateTestSignal(Int32, Double, Int32[], WaveType)

Declaration
public static double[] GenerateTestSignal(int sampleRate, double duration, int[] harmonics, WaveType waveType)
Parameters
Type Name Description
Int32 sampleRate
Double duration
Int32[] harmonics
WaveType waveType
Returns
Type Description
Double[]
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GetGain(Double[])

Declaration
public static double GetGain(double[] filterCoeff)
Parameters
Type Name Description
Double[] filterCoeff
Returns
Type Description
Double
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GetSignalOfAddedCosines(Int32, Double, Int32[])

returns a digital signal having sample rate, duration and harmonic content passed by user. Harmonics array should contain Hertz values of harmonics. i.e. int[] harmonics = { 500, 1000, 2000, 4000 }; Phase is not taken into account. Generate Cos waves rather than Sin because amplitude should return to 1.0 if done correctly.

Declaration
public static double[] GetSignalOfAddedCosines(int sampleRate, double duration, int[] freq)
Parameters
Type Name Description
Int32 sampleRate

sr of output signal.
Double duration

signal duration in seconds.
Int32[] freq

an array of frequency harmonics in Hertz.
Returns
Type Description
Double[]
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GetSignalOfAddedSines(Int32, Double, Int32[])

Declaration
public static double[] GetSignalOfAddedSines(int sampleRate, double duration, int[] freq)
Parameters
Type Name Description
Int32 sampleRate
Double duration
Int32[] freq
Returns
Type Description
Double[]
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PreEmphasis(Double[], Double)

The source signal for voiced speech, that is, the vibration generated by the glottis or vocal chords, has a spectral content with more power in low freq than in high. The spectrum has roll off of -6dB/octave. Many speech analysis methods work better when the source signal is spectrally flattened. The pre-emphasis filter is just a 1-order FIR filter, with gentle roll-off.

Declaration
public static double[] PreEmphasis(double[] signal, double coeff)
Parameters
Type Name Description
Double[] signal
Double coeff
Returns
Type Description
Double[]
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SubtractBaseline(Double[], Int32)

Declaration
public static double[] SubtractBaseline(double[] signal, int nh)
Parameters
Type Name Description
Double[] signal
Int32 nh
Returns
Type Description
Double[]
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Tests()

Declaration
public static void Tests()