Cancelling the Echo for a Generated Function using Convolution

So I generated an Echo for a function using Convolution, using the following code

[y,Fs] = audioread('Test1.wav');

%Definding Delay & attenuation_factor

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%Definding Impluse

h1=zeros(1,delay);%Impulse

h1(delay)=attenuation_factor; %Impulse at delay

h1(1)=1;

%Generating function with echo

z=conv(y,h1);

sound(z,Fs)

Now I want to cancel this echo again, and here is what i wrote so far

%Delcaring anothr Impluse

h2= [1,(zeros(1,delay))];

h2(delay)=-attenuation_factor;

h2(1)=1;

o=conv(h2,z);

But the final output function ( o ) is still having an echo, what am i doing wrong?

And why is the final output (o) domain is still beyond the original functin as shown below

[Mathieu NOE]

hello

your "anti echo" is not working because it's not the inverse process of the echo

in discrete (z) equations :

when you do the echo , : Y = (1 + attenuation_factor*z^(-delay)) * X

so this is basically a FIR filter. The best inverse of that would be the IIR filter : 1 / (1 + attenuation_factor*z^(-delay))

[Mathieu NOE]

see also :

Echo Cancelation - MATLAB & Simulink - MathWorks France