if exist('sound')~=2|exist('chirp.mat')~=2
disp('This routine requires sound and chirp.mat (a MATLAB .mat file)'),disp(' ')
else
clc,echo on 
%EXAMPLE 20 
load chirp;                             % Load chirp signal
z=y(1:1600);sound(z)                    % Truncate and play back
d=0.1;N=fix(8192*d);                    % Index N corresponding to delay d
z1=filter([1 zeros(1,N) 0.9],1,z);      % Pass chirp through echo filter
sound(z1)                               % Listen to filtered signal
z2=filter([1],[1 zeros(1,800) -0.4],z); % Pass chirp through reverb filter
sound(z2)                               % Listen to filtered signal
echo off %end of example
end