filtry filtry filtry

gistfile1.matlab

close all;

sampling_freq = 8000;
nyq_freq = sampling_freq / 2;

% Bandpass filter frequencies
freqs = [41 82 123];
for i=1:10
    fsize = size(freqs, 2);
    freqs = [freqs (freqs(fsize-1)*2)];
end

% Color table, for cute plotting
colors = [linspace(0,1,15)' logspace(0,1,15)'/10 linspace(1,0,15)'];

fig = figure(1);
hold on;

for i=2:size(freqs,2)-1
    width = freqs(i+1)-freqs(i-1);
    fqi = freqs(i);
   
    w1 = fqi - freqs(i-1);
    w2 = freqs(i+1) - fqi;
    
    fp = [fqi - w1 * 0.6, fqi + w2 * 0.6] ./ nyq_freq; % Pass frequencies
    fs = [fqi - w1, fqi + w2] ./ nyq_freq; % Stop frequencies
  
    % Filter design
    [N,wn] = buttord(fp, fs, 2, 10);
    [b,a] = butter(N,wn,'bandpass'); 
    
    % Plot frequency response
    [H,w] = freqz(b, a, 512, sampling_freq);
    plot(w, (abs(H)).^2, 'Color', colors(i,:));
    title('Frequency Response (Magnitude)');
    xlabel('Frequency (Hz)');
    ylabel('|H(\omega)|^2');   
end