how to get only the important bandwidth of a sound

Hello i am doing sound processing and i get all the time the [upper,~] = bandwidth(y); upper is around 220k either i speak or not when i use Amplitude Spectrum with out speaking i get this figure

my code for the plot is

 set(0,'DefaultFigureVisible','on')
 Y = fft(y);

 P2 = abs(Y/L);
 P1 = P2(1:L/2+1);
 P1(2:end-1) = 2*P1(2:end-1);
 f = Fs*(0:(L/2))/L;
 h(4)=figure;
 plot(f,P1)
 title('Single-Sided Amplitude Spectrum of X(t)');
 xlabel('f (Hz)')
 ylabel('|P1(f)|')

 =f;
 yyyyy=P1;

 indexmax = find(max(yyyyy) == yyyyy);
 xmax = xxxxx(indexmax);
 ymax = yyyyy(indexmax);

 strmax = ['Maximum = ',num2str(ymax),'    F =   ',num2str(xmax),'  hz'];
 text(xmax,ymax,strmax,'HorizontalAlignment','left');

i need to get only the important freq and if i speak to get near the 300-3000 of a human bandwidth or if i have a dog sound to get the dog bandwidth

Thanks

[John BG]

filtering the sound before plotting?

[Walter Roberson]

Please show the result of

which bandwidth(y)

I suspect you might be getting the linear algebra bandwidth, which would give you results in samples not in hertz.

[andreas ioannou]

Thanks for the respond Yes of course i filtering the sound. I use butter and a cut off freq.

My results of the which bandwidth(y)

>> which bandwidth(y)
built-in (C:\Program  Files\MATLAB\R2014b\toolbox\matlab\matfun\@double\bandwidth)  % double metho

i notice if i record for 5 sec i get bandwidth is near 220159 now i record 10 sec the bandwidth is near 438271

[Jan]

As Walter has assumed already: This is the linear algebra bandwidth of the array, which means the number of non-zero elements below or over the main diagonal: https://www.mathworks.com/help/matlab/ref/bandwidth.html

[andreas ioannou]

thanks jan, do u know any way to cut these freq in the pic? lets say to cut the freq below 0.01 of the P1

Answer 1

[Honglei Chen]

You may want to look into either powerbw or obw instead

https://www.mathworks.com/help/signal/ref/obw.html

https://www.mathworks.com/help/signal/ref/powerbw.html

HTH

[andreas ioannou]

thanks for the answer Honglei Chen. i have matlab R2014b i need to upgrade to r2016 for obw?

[Honglei Chen]

The reference page now actually indicates, at the bottom of the page, which release the function is introduced. I think both of them are introduced in R2015a, so you probably need to upgrade.

[andreas ioannou]

ok thanks Honglei Chen :)