Originally Posted by SAC
Just be aware - obtaining a patent does NOT imply that the idea is either sound nor that it works.
So be prepared to test the design...
Also, various QRDs such as the RPG Flutterfree also incorporate optional HH resonator panels placed behind the FF.
Agreed. Using the cavity behind QRD wells or other scattering surfaces for Helmholtz resonance is neither novel nor non-obvious, so that part of the patent, if stated too broadly, is likely unenforceable based on prior art. Perhaps some specific, limited implementation of it is patentable.
And as above, you can patent nearly anything original, whether it works or not. Consider the source (you'd probably trust a design from RPG), and if the source is unknown to you and no test data is available, you'll have to proceed with eyes and ears wide open.
Still, upon a quick look at the link, it looks interesting. Several questions come to mind about the effectiveness based on what's visible there, and I only skimmed the text, so I couldn't say more at this time.