help on matlab to get co-efficiency from FFT

hello.. i am noob in using matlab.. and i try to find many source and coding d. but still donno how to get the FFT co-efficiency using cheby2.

i record my voice in .wav and i try to get the co-efficiency of the fft frequency spectrum. below is some of my coding. I not sure correct or not, if got any wrong pls tell me. i will correct it.

[m d] = wavfinfo('C:\Documents and Settings\Pok\My Documents\GO2');
>> y = wavread('C:\Documents and Settings\Pok\My Documents\GO2');
>> [y,Fs,bits] = wavread('C:\Documents and Settings\Pok\My Documents\GO2');
>> Fs=4000;
bits=8;
x=fft(y,128);
freqz(x,8000);

Fs i change to 4000, and fft with 128 samples. And my question is i try to line it to the below code to get the co-efficiency. Thank you.

[B1,A1] = cheby2(2,40,0.1);
scaleb1 = round(B1.*256)
scaleb1 = scaleb1./256;
scalea1 = round(A1.*256)
scalea1 = scalea1./256;