singh,
I am not sure why the noise vs frequency you stated is 2*|sin(x)| the noise transfer function vs frequency would probably be something similar to N(s)=Const*(1+s/f1f)/(s)
For the filter you know the order so you pick the type by using butter, cheb, ellip etc obtain coefficients of numerator and denominator of the filter polynomial. Then generate the filter by calling freqs to check the response of just the filter. freqs returns a vector H at omega, multiply 20*log(H*N(omega)).
http://rfcooltools.com