LyonPassiveEar Class Reference
[Processing]

Lyon filterbank. More...

#include <LyonPassiveEar.h>

Inherits Marsyas::MarSystem.

Private Member Functions
void	myUpdate (MarControlPtr sender)
mrs_bool	setParametersIntern ()
	return true if the filterbank has to be (re-)created and set internal parameters
Static Private Member Functions
static Filter *	lyonCreateFilter (mrs_realvec firCoeffs, mrs_realvec iirCoeffs, mrs_string name)
	create a new filter
static mrs_real	lyonFreqResp (mrs_realvec firCoeffs, mrs_realvec iirCoeffs, mrs_real freq, mrs_real sRate, mrs_bool inDb=true)
	compute magnitude at a specific freq from a second order filter
static mrs_realvec	lyonSecondOrderFilter (mrs_real midFreq, mrs_real q, mrs_real sRate)
	compute second order filter coefficients
static mrs_real	lyonSetGain (mrs_realvec firCoeffs, mrs_realvec iirCoeffs, mrs_real newGain, mrs_real freq, mrs_real sRate)
	adjust the filter gain
Private Attributes
mrs_real	fs_
	sample rate
Series *	passiveEar_
	the actual filter cascade plus the post-processing (agc, channeldiff, etc.)

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Detailed Description

Lyon filterbank.

Lyon Passive Ear computation. Based on the code from the Auditory Toolbox by Malcolm Slaney.

Controls:

• mrs_natural/decimFactor [wr] : Decimation Factor - How much to decimate the model's output. Normally the cochlear model produces one output per channel at each sample time. This parameters allows the output to be decimated in time (using a filter to reduce aliasing. See the decimTauFactor parameter.)
• mrs_real/earQ [wr] : Quality Factor - The quality factor of a filter is a measure of its bandwidth. In this case it measures the ratio of the width of each band-pass filter at a point 3dB down from the maximum. Normally, critical band filters have a Q of about 8. Smaller values of earQ mean broader cochlear filters
• mrs_real/stepFactor [wr] : Filter stepping factor - Each filter in a filter bank is overlapped by a fixed fraction given by this parameter. The default value is given by earQ/32. Thus normal filters (q=8) are overlapped by 25%.
• mrs_bool/channelDiffActive [wr] : Channel Difference Flag - Adjacent filter channels can be subtracted to further improve the model's frequency response. This parameter is a flag; non-zero values indicate the channel differences should be computed.
• mrs_bool/agcActive [wr] : Automatic Gain Control Flag - An automatic gain control is used to model neural adaptation. This ?ag turns the adaptation mechanism on and off.
  • mrs_real/decimTauFactor [wr] : Filter Decimation Tau Factor - When the output of the cochlear model is decimated, a low pass filter is applied to each channel to reduce the high frequency content and minimize aliasing. The ?lter’s time constant (tau) is set to the decimation factor multiplied by this argument. Larger values for the taufactor mean less high frequency information is passed.
• mrs_realvec/centerFreqs [r] : mid frequencies of the calculated filter bands.

Definition at line 63 of file LyonPassiveEar.h.

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Member Function Documentation

void myUpdate

(

MarControlPtr

sender

)

[private, virtual]

filter coeffs; we will use second order filters only - these are the coefficients

Reimplemented from MarSystem.

Definition at line 330 of file LyonPassiveEar.cpp.

References MarSystem::addMarSystem(), realvec::create(), LyonPassiveEar::fs_, LyonPassiveEar::lyonCreateFilter(), LyonPassiveEar::lyonSecondOrderFilter(), LyonPassiveEar::lyonSetGain(), LyonPassiveEar::passiveEar_, and LyonPassiveEar::setParametersIntern().

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The documentation for this class was generated from the following files:

• /home/marsyas/marsyas/src/marsyas/LyonPassiveEar.h
• /home/marsyas/marsyas/src/marsyas/LyonPassiveEar.cpp