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Design IIR filter from absorption data

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Marius Tøndel Eliassen
Marius Tøndel Eliassen 2020 年 2 月 15 日
Hello!
As the title says, and I have got the coefficients. This:
f = [125 250 500 1000 2000 4000];
alpha = [0.09 0.2 0.5 0.7 0.8 0.9];
N = 1; % Filter order
Fs = 44100 % Sampling frequency
w = f/fs*2*pi; % Frequency in radians
R = sqrt(1-alpha);
% Find R(z) coefficients:
[b,a] = invfreqz(R,w,N,N);
How do I go about from here, as I need to visualize the filter, e.g. a plot of the magnitude response?
Best regards,
Marius

回答 (1 件)

Kaashyap Pappu
Kaashyap Pappu 2020 年 2 月 24 日
The fvtool could be what you are looking for. It will allow you to do the necessary visualizations.
Hope this helps!
  2 件のコメント
Marius Tøndel Eliassen
Marius Tøndel Eliassen 2020 年 2 月 24 日
That seems a good option for visualization. However my issue now is that my code doesn't give me a realistic filter shape for my coefficients. It should look like a low pass filter, but it is instead giving me something that looks like a shelving filter. It might be something I am missing in that code. What I am trying to do is depicted in the last section before the 3.1 mark in this article. Figure 1 shows it:

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