I have been working on this HW and I am not sure if I did something wrong. Here

Question

I have been working on this HW and I am not sure if I did something wrong. Here is my code.

%y[n]=x[n]+x[n-1]-x[n-4]-x[n-5];

%y[n]=y[n-1]-.9*y[n-2]+x[n]+x[n-1]

clear

clc

[x,fs] = audioread('toto.wav');

x = x(:,1);

dt = 1/fs;

t = 0:dt:(length(x)*dt)-dt;

plot(t,x); xlabel('Seconds'); ylabel('Amplitude');

num=[1 1 -.9];

den=[1 1 0 0 -1 -1];

sys=tf(num,den);

k=filter(num,den,x);

subplot(3,1,1);

plot(t,k);

title('filter response');

w=0:0.001:pi;

[h,om]=freqz(num,den,w)

m=20*log10 (abs(h))

an=angle(h)

subplot(3,1,2)

plot(om/pi,m)

title('mag spectrum of filter')

xlabel('freq')

ylabel('mag in db')

subplot(3,1,3)

plot(om/pi,an)

title('phase spectrum of filter')

xlabel('freq')

So I was playing around and when I use the 2nd equation at the top like in this code my filter response or the magnitude don't change. Why is that? Did I do something wrong? It doesn't even change if I change the values of the den either.

Explanation / Answer

Hello user,

Your num and den vectors are wrong

for first system

num=[1 1 0 0 -1 -1];

den=[1]

for second system

num=[1 1];

den=[1 -1 9];

Please let me know if you have any doubts

Thank You.

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