How to build the Frequency Response Function from the discrete time data (from hammer impact and accelerometer signal)?

Hi, I have the discrete time data from the excitation F and response signals X (using Data Acquisition Toolbox)

I then build the FRF from the direct(auto) power spectrum of F and X:

SF_f = pburg(F_co,4,16384); SX_f = pburg(X_co,4,16384); FRF = sqrt(SX_f./SF_f);

Using the above lines: - What is the magnitude (ordenate) of FRF? - Should I use any command to smooth the original signals? - Is pburg the most suitable command for such computation? - What kind of filter or order should I use?

Thank you in advance.

Best regards.