need to regenerate the original signal.

Hi, all I am motin. I am new in matlab. I fft a signal. and when i fft i take just half part of the fft value because replica is ignored and take the absolute value. now i simple change this value. now i want to regerate the original signal.
that means i need a mirror of the half value to get the whole signal. but how i give my code below.
[x, fs]=wavread('attack.wav');
block%6;
n=floor(length(x)/block);
x=x(1:block*n);

Y=reshape(x,n,block);
length(Y)

SP=zeros(n,block/2);
for i=1:n
St(Y(i,:),block);
SP(i,:)s(S(1:block/2));
end

imagesc(1:n,1:128,20*log10(SP')), axis xy, colormap(jet);

hi, Now i regenerate the original signal from the matrix SP. But how.
Plzzz can any one help me.... Start a New Thread