If you read the "readme" file that comes with the plugin, it indicates that it was written with the help of the SDRSharp crowd. Might not be listed due to encryption worries?!Yeh, sorry guys, I forgot to post the actual link to the site
Anyway, you've found it now, so all good.
I think this plugin is actually one of the more useful ones, if not just for the audio filter alone.
It should be listed on the SDRSHARP plugin page.
I might make a dedicated Thread letting people know about it.