Wanted to let you know about a RT60 calculator web app I put up last week. Limited use in most recording studios of course since you need a diffuse field, but may be helpful in ensuring evenness of absorption across the octave bands. The goal was to create a powerful and elegant tool that got away from the spreadsheet solutions we all use. About 400 finish/mounting combinations in the database and growing; Sabine, Eyring, Fitzroy, and Arau-Pruchades calculation models; dynamic ranging between empty and full occupancy, RT updating in realtime (Chrome or Safari). Register as a user to save or export as CSV.
More features and indeed more calculators/tools are in various states of development and will be included in time. Please let me know if you have any questions or constructive criticisms. If you like the calculator, please find it using your favorite search engine (searchterm "RT60 calculator") and let's get it on the front page.