Matlab: Spectrogram of white noise processed by a 500-Hz Butterworth lowpass filter

Matlab code:

clc;clear;close all;

 

Fs = 16000;  %Sampling frequency

Fco = 500;   %Cutoff frequency

order = 4;

[b, a] = butter(order, Fco/(Fs/2), 'low');

 

%Generate white noise

x=2*rand(16000,1)-1;

 

y = filter(b, a, x); %get time domain result

 

spectrogram(x,[],[],[],Fs,'yaxis');colormap hot;title('x');figure

spectrogram(y,[],[],[],Fs,'yaxis');colormap hot;title('y');

Result:

References:

Divide a speech utterance into 3 bands

Apply a LPF in the time and frequency using filter() and freqz()