How do i define the frequency band?

Here in this code i am doing a stft on my wav-file. There is no problem with that. At the beginning, i am defining my parameter, afterwards using my wav file and then applying the stft. Basically what i am doing is a real-time spectral analysis. Anyway my question is, how do i a frequency band? I want my signal to be separated in LOW/MEDIUM/HIGH. I want my vector to be saved, from 0-250 Hz in the LOW-Band, 250-5000 Hz in the MEDIUM-Band, 5000-22.05k Hz in the HIGH-Band. I advise you, to try my code in Matlab, if you don't understand it. Just take any wav-file. Btw my signal is plotted in the variable "Yres". Any solution is appreciated!

    NFA=2; %Every second picture is being plotted
    t_seg=0.03; %length of my segment in ms

    fftlen = 4096; 
    % Number of fft points

    [y,fs]=audioread('UnchainMyHeart.wav');
    t=linspace(0,length(y)/fs,length(y));
    plot(t,y)

    segl =floor(t_seg*fs); 
    windowshift=segl/2; 
    window=hann(segl); 
    window=window.'; 

    si=1; 
    %Start index
    ei=segl; 
    %End index

    AOS= length(y)/windowshift - 1;
    % Number of segments in my audio signal

    f1=figure;

    f=0:1:fftlen-1;
    f=f/(fftlen-1)*fs;

    Ya=zeros(1,fftlen);
    plot(f,Ya),axis([0 fs -90 50])

    grid on 

    n=0;

    for m= 1:1:AOS

    y_a = y(si:ei);
    y_a= y_a.*window;
    Ya=fft(y_a, fftlen);

    n=n+1;
    if n==1
      Yres=abs(Ya);
      else
      Yres=Yres+abs(Ya);
    end

    if n==NFA
      Yres=Yres/NFA;
      n=0;

      drawnow; 

    figure(f1);
    plot(f(1:end/2), 20*log10(abs(Yres(1:end/2))));

    a= (Yres);

    ylim([-90 50]);
    title('Spectrum of audio signal');
    xlabel('f(Hz)');
    ylabel('dB');

    grid on;

    end

    si=si+windowshift; 
    %Updating start index

    ei=ei+windowshift; 
    %Updating end index

    end

[Daniel kiracofe]

What do you want the data type to be within the frequency band? You want a vector of the time history? You want a vector that contains a sub-set of the FFT? You want a scalar that is the peak amplitude within the band for that slice?

If the first one, the easiest way is to not use FFT at all. Just use a few bandpass filters. e.g.

[b_lowf, a_lowf] = butter(2, [0, 250] / (fs/2) );
[b_midf, a_midf] = butter(2, [250, 5000] / (fs/2) );
low = filter( b_lowf, a_lowf, y);
etc.

If you want something other than that, could you be more specific about exactly what data type you are looking for?