Acoustic reflectivity(Beta) in CFX-Pre 14.5
 

Hi all,
I've searched all over the place but I haven't found exactly how acoustic reflectivity should be used. I can turn in on in the inlet and outlet(opening) and I've been told to look into the non-reflective option when having flow near Mach=1. Then it gives me the option to specify different scales?

Anyone willing to give me a nudge in the right direction?
Sorry if this has been asked before.