function f = min3(guess,r,om)
m=guess(1);
d = guess(2);
rho = guess(3);
k = guess(4);
c = 343;
rcompute = (m*om.*om-i*(d-rho*c)*om-k)./(m*om.*om-i*(d+rho*c)*om-k);
f=norm(r(:)-rcompute(:));