coeffs

Get filter coefficients

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Syntax

[B,A] = coeffs(obj)

Description

[B,A] = coeffs(obj) returns the coefficients of the filters created by obj.

example

Examples

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Open Live Script

Create a graphicEQ and then call coeffs to get its coefficients. The coefficients are returned as second-order sections. The dimensions of B are 3-by-(M * EQOrder / 2), where M is the number of bandpass equalizers. The dimensions of A are 2-by-(M * EQOrder / 2).

fs = 44.1e3;
x = 0.1*randn(fs*5,1);
equalizer = graphicEQ('SampleRate',fs, ...
                      'Gains',[-10,-10,10,10,-10,-10,10,10,-10,-10], ...
                      'EQOrder',2);

[B,A] = coeffs(equalizer);

Compare the output of the filter function using coefficients B and A with the output of graphicEQ.

y = x;
for section = 1:equalizer.EQOrder/2
     for i = 1:numel(equalizer.Gains)
        y = filter(B(:,i*section),A(:,i*section),y);
     end
end
audioOut_filter = y;

audioOut = equalizer(x);

subplot(2,1,1)
plot(abs(fft(audioOut)))
title('graphicEQ')
ylabel('Magnitude Response')

subplot(2,1,2)
plot(abs(fft(audioOut_filter)))
title('Filter function')
xlabel('Bin')
ylabel('Magnitude Response')

Figure contains 2 axes objects. Axes object 1 with title graphicEQ, ylabel Magnitude Response contains an object of type line. Axes object 2 with title Filter function, xlabel Bin, ylabel Magnitude Response contains an object of type line.

Open Live Script

Create the default gammatoneFilterBank, and then call coeffs to get its coefficients. Each gammatone filter is an eighth-order IIR filter composed of a cascade of four second-order sections. The size of B is 4-by-3-by-NumFilters. The size of A is 4-by-2-by-NumFilters.

[audioIn,fs] = audioread('Counting-16-44p1-mono-15secs.wav');

gammaFiltBank = gammatoneFilterBank('SampleRate',fs);

[B,A] = coeffs(gammaFiltBank);

Compare the output of the filter function using coefficients B and A with the output of gammaFiltBank. For simplicity, compare output from channel eight only.

channelToCompare = 8;
y1 = filter(B(1,:,channelToCompare),[1,A(1,:,channelToCompare)],audioIn);
y2 = filter(B(2,:,channelToCompare),[1,A(2,:,channelToCompare)],y1);
y3 = filter(B(3,:,channelToCompare),[1,A(3,:,channelToCompare)],y2);
audioOut_filter = filter(B(4,:,channelToCompare),[1,A(4,:,channelToCompare)],y3);

audioOut = gammaFiltBank(audioIn);

t = (0:(size(audioOut,1)-1))'/fs;

subplot(2,1,1)
plot(t,audioOut(:,channelToCompare))
title('Gammatone Filter Bank')
ylabel('Amplitude')

subplot(2,1,2)
plot(t,audioOut_filter)
title('Filter Function')
xlabel('Time (s)')
ylabel('Amplitude')

Figure contains 2 axes objects. Axes object 1 with title Gammatone Filter Bank, ylabel Amplitude contains an object of type line. Axes object 2 with title Filter Function, xlabel Time (s), ylabel Amplitude contains an object of type line.

Open Live Script

Create the default octaveFilterBank, and then call coeffs to get its coefficients. The coefficients are returned as second-order sections. The dimensions of B and A are T-by-3-by-M, where T is the number of sections and M is the number of filters.

[audioIn,fs] = audioread('Counting-16-44p1-mono-15secs.wav');

octFiltBank = octaveFilterBank('SampleRate',fs);

[B,A] = coeffs(octFiltBank);

Compare the output of the filter function using coefficients B and A with the output of octaveFilterBank. For simplicity, compare output from channel five only.

channelToCompare = 5;

audioOut_filter = filter(B(1,:,channelToCompare),A(1,:,channelToCompare),audioIn);
audioOut = octFiltBank(audioIn);

subplot(2,1,1)
plot(audioOut(:,channelToCompare))
title('Octave Filter Bank')

subplot(2,1,2)
plot(audioOut_filter)
title('Filter Function')

Figure contains 2 axes objects. Axes object 1 with title Octave Filter Bank contains an object of type line. Axes object 2 with title Filter Function contains an object of type line.

Input Arguments

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Object to get filter coefficients from, specified as an object of gammatoneFilterBank, octaveFilterBank, graphicEQ, or shelvingFilter.

Output Arguments

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Numerator filter coefficients, returned as a 2-D matrix or 3-D array, depending on obj.

Data Types: single | double

Denominator filter coefficients, returned as a 2-D matrix or 3-D array, depending on obj.

Data Types: single | double

Version History

Introduced in R2019a

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See Also

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