How can i determine the dominant frequency of a real sound signal recorded from microphone dirctly to matlab

I want to plot the line spectra of a sound data recorded from microphone in wav format

I am not sure whether this code gives the right value or not

    function line_spectra(z,Fs);

   clear all
  close all
  clc
  clf
  %Initialize variab
  [z,Fs] = wavread(normal_1.wav',2^17);Fs=44100Hz,data sample=131072

N=length(z); 

b=bin2dec(fliplr(dec2bin(0:N-1)))+1;

%make it bit reversed order

MC=z(b);

alfa=N/2;

beta=1;

%calculate Twiddle factor

for n=1:N/2

    W(n)=exp(-1i*2*pi*(n-1)/N);

    Wr(n)=cos(2*pi*(n-1)/N);

    Wi(n)=-sin(2*pi*(n-1)/N);

   end

%calculate FFT using inplace non-recursive FFT,radix-2

for h=1:(log(N)/log(2));

    b=2^(h-1);

    a=1;

    a0=1;

    for d=1:alfa

        c=1;

        for e=1:beta

            temp1=W(c)*MC(a+b);

            temp2=MC(a);

           MC(a)= MC(a)+temp1;

           MC(a+b)=temp2-temp1;

           a=a+1;

           c=c+alfa;

        end

        a=a0+2^(h);

        a0=a;

    end

    alfa=alfa/2;

    beta=beta*2;

 end

s=which('Exh_manifold_T3B.wav');%Modifying the figure window

set(gcf,'color',get(0,'DefaultUIcontrolBackgroundColor'),'NumberTitle',...
  'off','Name',s,'Resize','on','Menubar','none');

%calculate the frequency

fr = (0:(N/256)-1)*Fs/N;

%plot the figure

p = abs(MC(1:N/256));

 [Amax,f] = max(p);

 fprintf('Max.Magn. of Amp1. is %6.4f db/n and the freq f is %4.2f\n',Amax,f);

 pp=fftshift(p);

 plot(fr,pp,'k')

 xlabel('Frequency(Hz','Color','k','FontSize',12);

 ylabel('Magnitude','color','k','FontSize',12);

 title('Line spectrum plot for defective  engine   sound ','color','k','FontSize',12);

 set(text (170,1660,'Background','b','EdgeColor','r'),'color','k','FontSize',12);

QUESTION

1. fail to determine the fundamental frequency .
2. How can I filter it
3. the reading directly from the plot and from the code p = abs(MC(1:N/256));

 [Amax,f] = max(p);

 fprintf('Max.Magn. of Amp1. is %6.4f db/n and the freq f is %4.2f\n',Amax,f); not the same

[Rick Rosson]

Please format your code so that it is readable.

[Rick Rosson]

It is very unlikely that anyone will answer your question unless you format the question and code so that it is readable. Please review this page - Markup Help - to learn how.

I recommend that you put each MATLAB statement on a separate line, and that you insert two leading spaces at the beginning of each line of code so that the code is in a monospace font.

Otherwise, best of luck!

[Rick Rosson]

Why did you create your own implementation of the FFT? Why not use the fft function included in MATLAB?

[TESFAW]

I do not know where and when the

fft() is used, Sir! plz help me

Answer 1

[Image Analyst]

How about you just call fft() and look for the location (frequency) of the maximum value? Looks like you're doing that - was there any problem with it?

[TESFAW]

    Yes,Sir!

   the reading from the plot and the value displayed into the 

    command window is not the same.

    I do not know why ...

    I think the problem is in my code but I do not know which

    one is wrong