showing frequency and amplitude after doing fft on signal

[Rick T]

Greetings All I execute an fft on a wav file of a person saying "ahhh"
which shows the frequency and amplitude of the audio file.  The
problem I'm having is when I run it on a wav file it shows the
frequency 0hz with having the highest amplitude.  I'm not sure where
the problem is within my code and how I can fix it.

How does 0hz have the max amplitude?  The reason I'm trying to fix
this is that I want to find the frequency with the highest amplitude
in the wave file then run some calculation against it but running
calculations against 0hz doesn't make any sense to me especially when
I have to do multiplication with it.

When I look at **array_sort variable** it says the frequency is **0hz
and 0.117341 as it's amplitude.**

Here's the wave file an m file I'm using
http://dl.dropbox.com/u/6576402/questions/fft/11262012_44100ahh.wav

http://dl.dropbox.com/u/6576402/questions/fft/test_rtfftphase_question.m

    clear all, clc,clf,tic
    dirpathtmp=strcat('/tmp/');
    [vp_sig_orig, fs_rate, nbitsraw] =
wavread(strcat(dirpathtmp,'/nov26/11262012_44100ahh.wav')); %must be
mono
    fs=fs_rate;


    t_rebuilt=linspace(0,2*pi,fs); %creates same size time for new
signal as orginal signal good for error checking

    vp_sig_len=length(vp_sig_orig); %get sample rate from vp fs_rate
needs to be an even number?
        
    % Use next highest power of 2 greater than or equal to length(x)
to calculate FFT.
    nfft= 2^(nextpow2(length(vp_sig_orig)));
    % Take fft, padding with zeros so that length(fftx) is equal to nfft
    fftx = fft(vp_sig_orig,nfft);
    sigfft= fft(vp_sig_orig);
    sigifft=ifft(sigfft);
    sigphase = unwrap(angle(sigfft')); %get phase of orginal signal
    % Calculate the number of unique points
    NumUniquePts = ceil((nfft+1)/2);
    % FFT is symmetric, throw away second half
    fftx = fftx(1:NumUniquePts);
    % Take the magnitude of fft of x and scale the fft so that it is
not a function of the length of x
    mx = abs(fftx)/length(vp_sig_orig); %replaced for testing from stackexchage

    if rem(nfft, 2) % odd nfft excludes Nyquist point
      mx(2:end) = mx(2:end)*2;
    else
      mx(2:end -1) = mx(2:end -1)*2;
    end

    amp=mx;
    ampinv=abs(amp-max(amp));

    % This is an evenly spaced frequency vector with NumUniquePts points.
    freq_vect = (0:NumUniquePts-1)*vp_sig_len/nfft;
    freq=freq_vect';

    %get phase of new signal
    phase = unwrap(angle(fftx)); %get phase of orginal signal
    array=[freq,amp];
    array_sort=sortrows(array,-2); %sort by largest amplitude first

Any ideas?
PS: I'm using octave 3.2.4 on linux ubuntu 64bit
Thanks