%demonstration of echo cancellation
%following  Buck, Daniel and Singer,  Sec. 2.10
%Yao Wang, 1/20/2001

[x,fs]=wavread('morning.wav');
sound(x,fs); pause;
delay=10000;
a=0.5;
[sizex]=length(x);

y=zeros(sizex+delay,1);
y(1:delay)=x(1:delay);
y(delay+1:sizex)=x(delay+1:sizex)+a*x(1:sizex-delay);
y(sizex+1:sizex+delay)=a*x(sizex-delay+1:sizex);

sizey=length(y);

sound(y,fs);


z=filter(1, [1,zeros(1,delay-1),a],y);
pause;
sound(z,fs);

figure;
plot(x), axis([1,sizey,-0.25,0.25]);
figure;
plot(y), axis([1,sizey,-0.25,0.25]);
figure;
plot(z), axis([1,sizey,-0.25,0.25]);