# Export Audio with Volume Automation

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Hans Buchele on 5 Dec 2021
Answered: Mathieu NOE on 6 Dec 2021
Dear Community,
I would like to print a sinewave with volume automation in mathlab. I am already able to print a stereo wave file with a fixed amplitude. Is it possible to set time points with corresponding amplitude values?
fs = 44100;
i=1/fs;
t = 0:i:2;
phi = 0;
A = 1;
f = 220.0000;
x = A*sin((2*pi*f*t) + phi);
f = 220.0000;
y = A*sin((2*pi*f*t) + phi);
stereo_mtx = [x(:), y(:)];
audiowrite('stereo sound 3.wav', stereo_mtx, fs);
Any help is much appreciated! Thanks

Mathieu NOE on 6 Dec 2021
hello Hans
this is my suggestion
fs = 44100;
dt=1/fs;
t = 0:dt:2;
phi = 0;
A = 1;
f = 220.0000;
x = A*sin((2*pi*f*t) + phi);
f = 220.0000;
y = A*sin((2*pi*f*t) + phi);
% define volume envelopp by time index + amplitude set points
tt = [0 0.5 1.5 2];
yt = [0 1 0.75 0]; % linear fade in / fade out demo
w = interp1(tt,yt,t); % create window of same length as signal
y = y.*w; % apply window
stereo_mtx = [x(:), y(:)];
audiowrite('stereo sound 3.wav', stereo_mtx, fs);