Design IIR filter from absorption data

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

Answer 1

[Kaashyap Pappu]

The fvtool could be what you are looking for. It will allow you to do the necessary visualizations.

Hope this helps!

[Marius Tøndel Eliassen]

Thanks, I will check that out!

[Marius Tøndel Eliassen]

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:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.41.3912&rep=rep1&type=pdf