function test (N)

h1 = sinc((-N/2:N/2-1)/77).*hann(N)';
h2 = sinc((-N/2:N/2-1)/100).*hann(N)';

h1 = zeros(1,N);
h1(N/2+1) = 0.5;

v1 = sum((h1))

h2p = [h2 zeros(1,N/2)];
h12 = filter(h1,1,h2p);

plot(1:N, h12(N/2+1:N+N/2)/v1, 1:N, h1, 1:N, h2)
grid;