function [Sn] = ET_PreDesign_Sensitivity (f)

  x = f/200.;
  x2 = x .* x;
  x3 = x2 .* x;
  x4 = x2 .* x2;
  x5 = x3 .* x2;
  x6 = x3 .* x3;
   
  p1 = -4.05049;
  p2 = -0.687263;

  a0 = 185.623;
  b0 = 232.565;
  b1 = 31.1777;
  b2 = -64.7178;
  b3 = 52.242;
  b4 = -42.1643;
  b5 = 10.1708;
  b6 = 11.5317;

  c1 = 13.5793;
  c2 = -36.4586;
  c3 = 18.5625;
  c4 = 27.4297;
  S0 = 1.449936*10^-52;
  Sn = S0*(x.^p1 + a0.*x.^p2 + b0 * ( 1. + b1*x + b2*x2 + b3*x3 + b4*x4 + b5*x5 + b6*x6 )./(1. + c1*x + c2*x2 + c3*x3 + c4*x4));