How can i calculate the individual magnitude from my band?

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Denny Muttathil
Denny Muttathil 2017-2-3
评论： Nirja Mehta 2017-2-7
I took out 50ms from a signal and then apply a fft on it. Afterwards i separate it in 3 band. How can i calculate the individual magnitude in a band? Because i want to sum all of the magnitude into a value and then square it with 2. Therefore i would get the power from my band, which i want.
%%MATLAB
%_________________________________________
[y,fs]=audioread('Undertale - Megalovania.wav');
% audioread = Read WAV-file
% y = Vector, which contains audio signal
% fs = Sample Rate
% 'dontstopmenow' = WAV-file
%_________________________________________
%PARAMETER FOR STFT
%_________________________________________
t_seg=0.03; % Length of segment in ms
fftlen = 4096; %FFT-Points
%Definition of frequency bands
f_LOW= 1:200; %lower frequencies
f_MEDIUM= 201:600; %medium frequencies
f_HIGH= 601:1000; %higher frequencies
%__________________________________________
segl =floor(t_seg*fs);
% Length of segment, on which we use the fft
% "floor" rounds off the result
windowshift=segl/2;
% size of window which goes to the next segment
window=hann(segl);
%hann function
window=window.';
% From a row vector to a column vector
si=1;
%Start index
ei=segl;
%End index
N=floor( length(y)/windowshift - 1);
% Number of segements in audio signal
f1=figure;
% New window
f=0:1:fftlen-1;
f=f/fftlen*fs;
% frequency vector
Ya=zeros(1,fftlen);
for m= 1:1:N
y_a = y(si:ei);
y_a= y_a.*window;
Ya=fft(y_a, fftlen);
Yb=abs(Ya(1:end/2));
drawnow; %Updates graphical objects
figure(f1);
plot(f(1:end/2), 20*log10(Yb));
%STFT __Audio signal after stft every 50ms
%%L,M,H - Bands
subplot(3,1,1)
y_low = abs(Ya(f_LOW));
ya_low = sum(y_low).^2;
plot(f_LOW,y_low);
ylim([-90 50]);
title('Spektrum (LOW)');
xlabel('f(Hz)');
ylabel('dB');
grid on
subplot(3,1,2)
y_medium = Ya(f_MEDIUM);
plot(f_MEDIUM,y_medium);
ylim([-20 30]);
title('Spektrum (MEDIUM)');
xlabel('f(Hz)');
ylabel('dB');
grid on
subplot(3,1,3)
y_high = Ya(f_HIGH);
plot(f_HIGH,y_high);
ylim([-20 30]);
title('Spektrum (HIGH)');
xlabel('f(Hz)');
ylabel('dB');
grid on;
si=si+windowshift;
% start index updated
ei=ei+windowshift;
% end index updated
end
  1 个评论
Nirja Mehta
Nirja Mehta 2017-2-7
Do you mean to compute the following? Band Power
There are multiple functions in Signal Processing Blockset that helps you anaylze spectral content of a signal. Spectral Estimation
Also, do change plot(f_LOW,y_low) to plot(f_LOW,ya_low) on Line 52.

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