Understanding FFT analysis of sound .wav file

Hey I plotted this function of my recorded voice using an fft, I dont quite understand the corresponing frequency response graph, can someone help me see where I went wrong? It is a sample of my own voice, but the fft analysis shows frequency components at much higher frequencies, i.e. 700Hz and 1200Hz. I posted the code, and the graph below.

[y,Fs] = audioread(filename);
Length = length(y)
Mono = (y(:,1)+y(:,2))/2;
y = Mono;
time=(1:length(y))/Fs;
F = 1./time;
NFFT = 2^nextpow2(Length)
f = Fs/2*linspace(0,1,NFFT/2+1);
Y = fft(y,NFFT)/Length;
plot(f,2*abs(Y(1:NFFT/2+1)))

[Star Strider]

Context: http://www.mathworks.com/matlabcentral/answers/303241-help-with-fourier-analysis-of-wav-signal

[Brendan Zotto]

Does the frequency make sense?

Answer 1

[Star Strider]

That looks appropriate for a speech signal. Speech is generally considered to be band-limited to a maximum frequency of 6 kHz, and in the analog telephone days was actually limited to 6 kHz, and radiotelephone transmitters limited it to 3 kHz to conserve bandwidth. The fundamental is usually in the range of 500-1200 Hz (lower for males and higher for females). There are probably more references available, but the most appropriate one i can find just now is Human Speech Spectrum, Frequency Range, Formants.