The document provides a detailed Matlab tutorial on generating and manipulating audio signals using a sound card. It explains creating analog input objects, reading and playing .wav files, and various sound effects including speed adjustment, volume control, and digital delay. Additionally, it discusses the importance of sampling frequency to avoid signal aliasing and includes several references for further study.

1. STUDENTS:
LƯU HOÀNG TÂN 40902371
PHẠM HOÀNG TUẤN 40903123
TUTOR: PhD HA HOANG KHA
AUDIO SIGNALS WITH
SOUNDCARD
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2. 2
CONTENT
I
IIGenerate some sound efect
Stimulate and draw the spectrum

3. I. Waveform and the spectrum of audio signal
captured from soundcard
3
Overview diagram

4. 4
 Create an analog input device object
ai = analoginput('winsound');
addchannel(ai,1);
 Changing object properties
ai.SampleRate = Fs;
ai.SamplesPerTrigger = duration*Fs;
ai.TriggerType = 'Manual';
 Get data
start(ai);
trigger(ai);
[data, t] = getdata(ai);
delete(ai);
clear ai;
MATLAB daq toolbox

5. MATLAB program
5

6. 6
Fs > 2B
Fs < 2B
Comment : If sampling frequency Fs < 2B, the signal spectrum
is aliased by its image.
Signal spectrum with sampling frequency Fs

7. 7
Consider an sinusoidal signal 0.6V amplitude, frequency 5kHz as
the input.

8. 8
In case Fs = 8000Hz
In the right window, there are two spectral line at -3kHz and 3kHz
which does not match the spectrum of 5kHz sinusoidal signal

9. 9
In case Fs=48000Hz
The signal spectrum does match the one of 5kHz sinusoidal signal .

10. 10
II. Create sound effects
Matlab program
The program read
a .wav file which
was build from
stereo audio signal
sampling at
44.1kHz. With the
data, we generate
several sound
effect.

11. 11
MATLAB functions
[x,fs] = wavread(‘road.wav’) : read file name road.wav
and store the value to array x.
sound(x,fs) : play the wav file converted to x in the previous
description.
soundsc(x,Fs) : scale the sound of the wav file. Scaling a
signal means changing its frequency or amplitude.

12. 12
The signal and its spectrum by playing file road.wav

13. 13
Effects
 Changing the Speed
[hootie,fs]=wavread('hootie.wav'); %loads Hootie
Soundsc(hootie,fs/1.5) % How slow can you go?
soundsc(hootie,fs*1.5) % The Chimpmonks!
 Changing Volume
soundsc(m*hootie,fs)
 Reverse
y=[1;2;3;4;5];
y2=flipud(y); %reverse the array y

14. 14
 Digital Delay Experiment
out = x; % set up a new array, same size as old
one
N=10000; % delay amount N/44100 seconds
for n=N+1:length(left)
out(n)=x(n)+x(n-N); % approximately ¼ second
echo
end
soundsc(out,fs) % new echo
 Digital Tone Control ( Low Pass Filter)
[hootie,fs]=wavread('hootie.wav'); % loads Hootie
out=hootie;
for n=2:length(hootie)
out(n,:) = 0.9*out(n-1,:)+hootie(n,:);
end
soundsc(out,fs); % low pass filtered

15. 15
The signal spectrum at the output of LPF

16. References
http://www.mathworks.com/help/daq/daq.html
https://www.mathworks.com/products/daq/supported/sound-cards.html
https://www.mathworks.com/products/daq/examples.html?file=/products/de
mos/daq/acquiring_data/acquiring_data.html
https://www.mathworks.com/help/daq/examples/discover-all-other-devices-
using-the-legacy-interface.html?prodcode=DA&language=en
http://www.mathworks.com/help/matlab/ref/wavread.html?cmdname=wavrea
d
http://www.mathworks.com/access/helpdesk/help/techdoc/ref/ref.shtml
http://homepages.udayton.edu/~hardierc/ece203/sound.htm
http://class.ee.iastate.edu/mmina/EELC-Cpree/Labs/Lab4-music.htm
http://comm14.blogspot.com/2013/06/audio-effects-processor-matlab-
project.html
http://www.h6.dion.ne.jp/~fff/old/technique/auditory/matlab.html
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