How to Add random noise to a signal

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lady bird
lady bird 2015-5-20
评论： Enac Gallardo-Diaz 2024-10-10
hello all
please can ou help me out adding a noise signal to my system.
i tried adding a sinus function , but i would like to add a random noise signal rather than the sinus function. I'm running simulation from 1 to 3000
if k>1000 & k<2000
dk(k)=sin(12*k*pi*ts);
x=A*x+B*u(k)+B*dk(k);
else
dk(k)=0;
x=A*x+B*u(k);
end
Thank you so much
Best regards
  2 个评论
chris matthew
chris matthew 2020-3-14
移动：DGM 2023-3-4
how to add noise to audio not for signal
Image Analyst
Image Analyst 2020-3-14
移动：DGM 2023-3-4
What does that mean? Audio IS a signal. You can't add noise to audio without adding it to the signal that defines the audio waveform.

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回答（6 个）

Thorsten
Thorsten 2015-5-20
x = linspace(-2*pi, 2*pi);
plot(sin(x) + 0.5*rand(size(x)))
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Tuhin Choudhury
Tuhin Choudhury 2020-3-16
编辑：Tuhin Choudhury 2020-3-16
Hi,
Thanks. This would be more of a flexible scaling of the noise w.r.t the input signal.
BR- Tuhin
Enac Gallardo-Diaz
Enac Gallardo-Diaz 2024-10-10
Hi,
This is a great solution. I want to point a subtle improvement. Using this algorithm you would end up with a noisy signal that is always above the original one. This is because rand() gives random numbers ranging from 0 to 1.
Usually, when you want to add noise to a given data you want the noisy function to be centered in the original. To do so you just need to generate random numbers going from -1 to 1. Simply replace
rand(size(noise_free_signal))
with
2*(rand(size(noise_free_signal))-0.5)

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Image Analyst
Image Analyst 2015-5-20
So just use rand() instead of sin().
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Prajakta Yeola
Prajakta Yeola 2017-10-29
Can we use the same code if audio signal is .wav file? i.e. if x is a .wav file
Image Analyst
Image Analyst 2017-10-29
Sure, just figure out the amplitude and add it
yNoisy = yOriginal + amplitude * rand(1, length(yOriginal));

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KL
KL 2015-5-20
Did you check the gaussian noise function?
  2 个评论
lady bird
lady bird 2015-5-20
i found a awgn function but i dont know how to use it in my case?
KL
KL 2015-5-20
There's a difference between wgn() and awgn(). With the latter, you add noise throughout the whole range. I understand you want to add noise between certain time intervals. So in this case, I would suggest to use wgn(). At the moment I do not have the toolbox to use this function. Anyhow you shall use this function to calculate the noiseSignal variable according to @Image Analyst's code.

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Aparna Gupta
Aparna Gupta 2017-6-21
Can anyone please help me with the code to add awgn noise to an eeg signal,which i have taken from a database and the file is of .mat type?
Mohammad Sohail Khan
编辑：DGM 2023-3-4
t = 0:pi/100:40;
x = cos(pi/10*t)+0.5*randn(size(t));
plot(t,x)
Then you know where pi/2, 3pi/4 etc are.
Adewale Obaro
Adewale Obaro 2018-9-24
编辑：DGM 2023-3-4
N = 1000;
t = 0:1/N:2;
x = sin(2*pi*5*t);
Noise = x + randn(1,N)';
plot(t,Noise);
title('Noise in the Amplitude interval (0,0,1,0)');
ylabel('Amplitude [m]')
xlabel('Time [s]')

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