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

Question

TESFAW 2014-8-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/146711-how-can-i-determine-the-dominant-frequency-of-a-real-sound-signal-recorded-from-microphone-dirctly

编辑： Walter Roberson 2018-6-23

采纳的回答： Image Analyst

在 MATLAB Online 中打开

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

fail to determine the fundamental frequency .
How can I filter it
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

4 个评论
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Rick Rosson 2014-8-11

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

TESFAW 2014-8-11

在 MATLAB Online 中打开

I do not know where and when the

fft() is used, Sir! plz help me

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Answer 1

Image Analyst 2014-8-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/146711-how-can-i-determine-the-dominant-frequency-of-a-real-sound-signal-recorded-from-microphone-dirctly#answer_148112

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?

1 个评论
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TESFAW 2014-8-11

在 MATLAB Online 中打开

    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