Muhsin Zerey asked . 2024-03-09

How can I add a low pass filter after each delay line in my multi channel feedback delay network

in = [ 1; 0 ]; % Dirac Impulse
Fs = 44100;
in = [in; zeros(3*Fs,1)]; % Space for reverb
% Define delay parameters
       %Hadamard Matrix as feedback matrix
H = 0.75*hadamard(16);




feedbackGain =[0.1,-0.15,-0.2,0.25,-0.3,0.35,0.4,-0.45,-0.5,0.55,0.6,-0.65,-0.7,-0.75,-0.8,0.85]; %0.1,0.15,0.2,0.25,0.3,0.35,0.4,0.45,0.5,0.55,0.6,0.65,0.7,0.75,0.8,0.85
wetGain = [0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7,0.7]; % adjust to control wet signal level
% Convert delay time to samples
delaySamples = [101,233, 439,613, 853,1163, 1453,1667 , 1801,2053, 2269,2647, 3001,3607, 4153,4591]; %0.02s, 0.03, 0.04, 0.05 881, 1009, 1321,1511, 1777, 1999, 2203, 2351
                                                               %101, 439, 853, 1453 , 1801, 2269, 3001, 4153

%Summe delays = 30644


% delaySamples = [1200, 1800, 2200,2500];
% Create an empty array to store delayed audio
delayedAudio = zeros(size(in));
delayedAudio2 = zeros(size(in));
delayedAudio3 = zeros(size(in));
delayedAudio4 = zeros(size(in));
delayedAudio5 = zeros(size(in));
delayedAudio6 = zeros(size(in));
delayedAudio7 = zeros(size(in));
delayedAudio8 = zeros(size(in));
delayedAudio9 = zeros(size(in));
delayedAudio10 = zeros(size(in));
delayedAudio11 = zeros(size(in));
delayedAudio12 = zeros(size(in));
delayedAudio13 = zeros(size(in));
delayedAudio14 = zeros(size(in));
delayedAudio15 = zeros(size(in));
delayedAudio16 = zeros(size(in));




delayedAudios =[delayedAudio,delayedAudio2,delayedAudio3,delayedAudio4,delayedAudio5,delayedAudio6,delayedAudio7,delayedAudio8,delayedAudio9,delayedAudio10,delayedAudio11,delayedAudio12,delayedAudio13,delayedAudio14,delayedAudio15,delayedAudio16];
delayedAudios(1,:) = 1;


% Apply delay effect

for i = 1:length(in)-2*max(delaySamples)
     for k = 1:16
        if delayedAudios(i+delaySamples(k),k) == 0
        delayedAudios(i+delaySamples(k),k) = feedbackGain(k)*delayedAudios(i,k);
        end
        
     end      
 
     for k = 1:16
        for j = 1:16
           if delayedAudios(i+delaySamples(j)+delaySamples(k),k) == 0 && k~= j 
            delayedAudios(i+delaySamples(j)+delaySamples(k),k) = H(j,k)*delayedAudios(i+delaySamples(j),j);
           end
        end
     end     
end


%Original and Mix together

for k = 1:16
    delayedAudios(:,k) = wetGain(k)*delayedAudios(:,k);
end

%outputAudioM = delayedAudios(:,16) + delayedAudios(:,15) + delayedAudios(:,14) + delayedAudios(:,13) + delayedAudios(:,12) +delayedAudios(:,11) +delayedAudios(:,10) +delayedAudios(:,9)+delayedAudios(:,8) +delayedAudios(:,7) +delayedAudios(:,6) +delayedAudios(:,5) +delayedAudios(:,4) +delayedAudios(:,3) +delayedAudios(:,2 )+delayedAudios(:,1);
outputAudioM = sum(delayedAudios,2);
outputAudioM(1) = outputAudioM(1)*0.02;

%Low pass filtering + phase adjusting
d = designfilt('lowpassfir','FilterOrder',4 ,'CutoffFrequency',2000,'SampleRate', Fs);
y = filtfilt(d,outputAudioM);


% %Write the output audio to a new file and plot
audiowrite('output_audio_with_delay.wav', y, Fs);
plot(y);

% Play the output audio
sound(y,Fs);

lowpass filtering , feedback , delay network , Signal Processing , Audio Toolbox