Need help with generating an echo for an Audio signal

Hello, I want to generate an echo for an audio signal, then output both signals (the orginal, and the delayed( and attenuated) version).

Here is my code

%Reading the main audio

......

%Definding time

N = length(y);

t = (0:N-1)/Fs;

%Definding the echo

delay = 10000

Z = zeros(delay,1);

Ynew = [Z;y(1:end-delay)];

%Plotting both functions

subplot(2,1,1);

plot(t,y);

subplot(2,1,2);

plot(t,0.1*Ynew);

Now my problem that when i run the code, the echo functino stops at the same instance as the orginal one, but what i want is i want the domain of the echo signal to be more than the original one by the delay value. ( I want the Echo function to contiune after 3).

[Abdelrhman Abdelfatah]

Also io there a way to ouput both functions together using "Sound" Command?

Answer 1

[Voss]

Avoid cutting off the echo, i.e., use y instead of y(1:end-delay)

%Definding the echo
delay = 10000
Z = zeros(delay,1);
% Ynew = [Z;y(1:end-delay)];
Ynew = [Z; y];

And, to combine them (so you play them together at once or do anything else), you can add them together, but they need to be the same length, so append zeros to the end of original signal first:

y_combined = [y; Z] + 0.1*Ynew; % with attenuated Ynew (probably define Ynew to be attenuated in the first place instead)

For clarity, here's a complete piece of code doing those things with a random signal:

% some random signal y
y = 0.002*randn(100000,1).*exp(1.5*mod(-(1:100000).'/20000,1)).*repelem(randi(10,5,1),20000,1);
Fs = 50000;

%Defining time 
N = length(y);
t = (0:N-1)/Fs;

%Defining the echo
delay = 10000;
Z = zeros(delay,1);
% Ynew = [Z;y(1:end-delay)];
Ynew = [Z; 0.1*y]; % with attenuation built-in

% combining original and echo
y_combined = [y; Z] + Ynew;

% new time vector, for the new signal length:
t_new = (0:numel(Ynew)-1)/Fs;

%Plotting all signals
subplot(3,1,1);
plot(t,y);
xlim(t_new([1 end]))
ylabel('Original')

subplot(3,1,2);
plot(t_new,Ynew);
xlim(t_new([1 end]))
ylabel('Delayed')

subplot(3,1,3);
plot(t_new,y_combined);
xlim(t_new([1 end]))
ylabel('Combined')
xlabel('Time')

[Abdelrhman Abdelfatah]

Thank you so much!

[Voss]

You're welcome!

[Abdelrhman Abdelfatah]

What if i want to adjust this code to generate infinite echo instead of a single one?

[Voss]

Infinite echos is a lot of echos. Maybe figure out how 2 echos would work first. From that, I'm sure you'll see how any (finite) number of echos would work.

[Abdelrhman Abdelfatah]

Thank you so much, this is exactly what i did, and it's working fine now, and even did the infinite cancellation too!

[Voss]

Excellent!

Answer 2

[Jonas]

just append zeros to the original signal, prepend the same amount to a copy of your original to generate the echo and add them up then

[originalSig; delay]+myAttenuation*[delay; originalSig]

you can add the signals up like above to hear the combined version or you concatenate both arrays horizontally to hear the original on one ear and the delayed signal on the other.

[Abdelrhman Abdelfatah]

Thanks for your quick answer, but not sure if i understood what u are trying to say

[Jonas]

ok you have your original signal y, which you want to overlay with an echo of itself. to prepare the echo addition, append the wanted zeros matrix called delay

preparedOriginal=[y;delay];

the echo has a specific delay, and attenuation and we add the delay before

attenuation=0.2;
echo=attenuation*[delay;y];

to hear the combined version use

sound(preparedOriginal+echo,fs)

with fs being the sampling frequency of your original signal

to hear the original on the left ear and the echo on the right, use

sound([preparedOriginal, echo],fs)

[Abdelrhman Abdelfatah]

Thank you so much for taking the time to explain!