t=1:4*1024;
T=1024;
om=2*pi/32;
x=sin(om*t);
y=3*x+10*(rand(1,4*1024)-.5);;;
x=x-mean(x);
y=y-mean(y);

%Cxy=cohere(x,y);
nfft=256;

figure(1);
[C f]=cohere(x,y,nfft,1,hanning(nfft),128);
plot(f,C);

load uwlow;

figure(2);
[C f]=cohere(u,h,nfft,1,hanning(nfft),128);

plot(f,C);