Acoustics Consultants
Question: Philip T. / Acoustics Consultant
(Middleton, Manchester, U.K.)
I have to admit that I am stretching my wings a bit and designing my
first large live music recording studio. My client has expressed that
they want a sound diffusive ceiling in the studio. I have read about QRD
theory, but it seems like it has been around for decades. Has there been
any advances that I should consider, or is QRD theory still
state-of-the-art?
Sound-Answers.com
Quadratic residue diffuser (QRD) theory has been around for decades and
it is well documented in books and journals. QRD phase gratings have
worked well in the past for many installations primarily because there
was nothing better available. Not true these days though. Dr. Peter
D’Antonio (RPG Diffusor Systems, Inc.) and Professor Trevor Cox
(University of Salford) have advanced sound diffusion in the built
environment past QRD theory. QRDs are symmetrical about a central axis.
When multiple QRDS are placed next to one another in a series, you begin
to get the negative effects of extreme lobing due to the periodicity. In
other words the extreme lobing begins to resemble specular reflections
again. D’Antonio and Cox developed asymmetrical phase gratings that can
be aperiodically modulated during installation. They realize better
diffusion and scattering in part due to the advanced design of the
diffusers themselves, but also gain even better diffusion and scattering
as a result of the aperiodic modulation of the base units during
installation. To learn more, we recommend reading Acoustic Absorbers
and Diffusers, Theory Design and Application (D’Anontio & Cox,
Taylor & Francis, New York). The book is available on-line at
www.amazon.com for
142.92 USD. Or, simply call Peter D’Antonio at RPG Diffusor Systems at
301-249-0044; he is always willing to talk to people about sound
diffusion.
Beyond the question ~ We encourage you to consider RPG’s
Waveform Bicubic (8” / 200 mm depth, 1/4" / 6 mm material thickness) for
the ceiling over your studio project. The hemispherical distribution
pattern will help diffuse sound in all directions throughout the studio
and the futuristic forms will add flare to the aesthetics.
