From Everything.Sucks

WinFLAG software does the job of calculating the absorption coefficient, the impedance and the sound reduction index for constructions combining different material layers such as porous materials (e.g. mineral wool), solid and perforated plates (slotted, with circular holes, microperforated). WinFLAG also calculates the attenuation of noise in ducts, e.g. air-conditioning ducts, lined with the chosen layers.

An unhappy customer shared his expeirence, "I called the company...they needed information I didn't have...back to the seller...still didn't get proper information. Returned it. Considered buying directly from the manufacturer, but after reading reviews, other clients had similarly bad experiences with the setup and registration...having to make multiple calls to get it registered."