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STUDENTS:LƯU HOÀNG TÂN 40902371PHẠM HOÀNG TUẤN 40903123

TUTOR: PhD HA HOANG KHA

AUDIO SIGNALS WITH SOUNDCARD

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CONTENT

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IIGenerate some sound efect

Stimulate and draw the spectrum

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

Overview diagram

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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

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MATLAB program

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Fs > 2B

Fs < 2B

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

Signal spectrum with sampling frequency Fs

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

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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

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In case Fs=48000Hz

The signal spectrum does match the one of 5kHz sinusoidal signal .

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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.

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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.

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The signal and its spectrum by playing file road.wav

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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

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Digital Delay Experimentout = 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

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The signal spectrum at the output of LPF

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References

http://www.mathworks.com/help/daq/daq.htmlhttps://www.mathworks.com/products/daq/supported/sound-cards.ht

mlhttps://www.mathworks.com/products/daq/examples.html?file=/prod

ucts/demos/daq/acquiring_data/acquiring_data.htmlhttps://www.mathworks.com/help/daq/examples/discover-all-other-d

evices-using-the-legacy-interface.html?prodcode=DA&language=enhttp://www.mathworks.com/help/matlab/ref/wavread.html?cmdname

=wavreadhttp://www.mathworks.com/access/helpdesk/help/techdoc/ref/ref.sht

mlhttp://homepages.udayton.edu/~hardierc/ece203/sound.htmhttp://class.ee.iastate.edu/mmina/EELC-Cpree/Labs/Lab4-music.htmhttp://comm14.blogspot.com/2013/06/audio-effects-processor-matlab

-project.htmlhttp://www.h6.dion.ne.jp/~fff/old/technique/auditory/matlab.html