How to add low frequency noise to the signal?

How to add low frequency noise (less than 3Hz) to signal in matlab?

Answer 1

[Mathieu NOE]

hello

this is a simple demo showing a sine signal corrupted by a low frequency noise . You can adjust the parameters to your own needs

Fs = 1000;
samples = 10000;
dt = 1/Fs;
t = (0:samples-1)*dt;
y = 3*sin(2*pi*1*t); % signal - adjust amplitude to your needs
noise =  1.5*randn(size(t)); % noise (before filtering) - adjust amplitude to your needs

% low pass filter : Butterworth filter
NN = 2; % filter order
fc = 3; % cut off frequency (Hz)
Wn = fc/(Fs/2); % normalized cut off frequency 
[B,A] = butter(NN,Wn);
noise_filtered = filter(B,A,noise); % noise (after LP filtering)
y_noisy = y+noise_filtered; % signal + noise 

figure(1)
plot(t,y,t,y_noisy);legend('signal','signal + noise');