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Signal_bruit_et_fourier.png (download)‎ (610 × 461 pixels, file size: 5 KB, MIME type: image/png)

## Summary Edit

Spectre (transformée de Fourier) d'un signal bruité

Spectrum (Fourier transform) of a signal with noise

Auteur/author : Christophe Dang Ngoc Chan (cdang)

```clear;clf;

// ******************
// variable ajustable

p=0.1; // pas

// ******************
// variables de base

x=[0:p:20*%pi]'; // x du sinus
N=size(x);
n=N(1,1); // nombre de points
s=1/p*(1:n); // fréquences

// nombres aleatoires, loi uniforme

y2=0.2*(rand(n,1)-0.5);

// ******************
// Calcul

y1=sin(x);
y3=y1+y2;
z1=abs(fft(y1))^2;
z2=abs(fft(y2))^2;
z3=abs(fft(y3))^2;

for i=1:n
if z1(i)>500 then z1(i)=500; end
if z3(i)>500 then z3(i)=500; end
end

// ******************
// affichage

subplot(3,2,1)
plot2d(x,y1,style=2,rect=[0,-1.1,60,1.1])
xtitle('signal sinusoïdal','Temps','Intensité')

subplot(3,2,2)
plot2d(s,z1,style=2,rect=[0,0,0.03,50])
xtitle('TF signal sinusoïdal','Fréq.','Puissance')

subplot(3,2,3)
plot2d(x,y2,style=2,rect=[0,-1.1,60,1.1])
xtitle('bruit','Temps','Intensité')

subplot(3,2,4)
plot2d(s,z2,style=2,rect=[0,0,0.03,50])
xtitle('TF bruit','Fréq.','Puissance')

subplot(3,2,5)
plot2d(x,y3,style=2,rect=[0,-1.1,60,1.1])
xtitle('signal sinusoïdal bruité','Temps','Intensité')

subplot(3,2,6)
plot2d(s,z3,style=2,rect=[0,0,0.03,50])
xtitle('TF signal sinusoïdal bruité','Fréq.','Puissance')
```

## Licensing Edit

I, the copyright holder of this work, hereby publish it under the following license:
 Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License."
 This page uses content from the Wikimedia Commons. The original content was at File:Signal bruit et fourier.png. The list of authors can be seen in the page history. As with this Psychology Wiki wiki, that portion of the content of Wikimedia Commons is available under the GNU Free Documentation License.

## Appears on these pages of

• ### Signal-to-noise ratio

Assessment| Biopsychology| Comparative| Cognitive| Developmental| Language| Individual...

## File history

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Date/Time Thumbnail Dimensions User Comment current 11:29, November 5, 2007 610 × 461 (5 KB) PhloxBot (Talk | contribs) == Summary == Spectre (transformée de Fourier) d'un signal bruité ---- Spectrum (Fourier transform) of a signal with noise Auteur/author : Christophe Dang Ngoc Chan (cdang) Réalisé avec/made with [http://www.scilab.org/ Scilab] cl