Well balanced acoustical designs
contain an appropriate combination of absorption, reflection,
and diffusion. In many applications, however, limited budget or
surface treatment thickness preclude the use of diffusion. Absorptive,
fabric wrapped panels are specified for lack of an alternative.
Unfortunately, wide area application may lead to an acoustically
"dead" environment without "air" or ambiance.
To solve this problem, RPG® developed the first flat, zero
depth diffusor: the Flatffusor™. The Flatffusor™ simultaneously
provides uniform sound diffusion at high and mid band frequencies
and crosses over to pure absorption below the diffusive cutoff.
The energy that is not diffused is absorbed.
It's Digital!
To accomplish this goal, RPG® developed a new planar 2 dimensional
binary reflection amplitude grating consisting of a 31 x 33 element
array of 1,023 half inch square absorptive or reflective areas.
The reflective areas (black in upper illustration) map to the
"1" bit and the absorptive areas (white) map to "0",
or vice versa. The distribution of these resorptive binary elements
is based on a 2 dimensional optimal binary sequence with a flat
power spectrum. The resulting variable impedance surface forms
a binary reflection amplitude grating suggested by James Angus.
This surface is in contrast to RPG®’s reflection phase
gratings, which use phase variation rather than amplitude variation
to provide diffusion. The Flatffusor™ provides diffusion
about an octave above the frequency whose wavelength is twice
the size of the binary element. This explains the limitation of
traditional variable impedance arrays. For example, 1' x 1' panels
provide diffusion up to about 1 kHz. Remaining high frequency
reflections would still corrupt speech and music quality.
The Flatffusor™ consists of a binary mask attached to the
face of a semi rigid fiberglass panel. The panel is upholstered
in a decorative fabric to completely conceal the acoustical functionality.
The Flatffusor™ panel extends the acoustical performance
of traditional absorptive fabric wrapped panels, allows wide area
coverage without excessive deadening, and offers an alternative
to RPG®’s line of traditional phase grating diffusors.
The Flatffusor™ panel is ideal for any facility that needs
reflection control from a decorative, upholstered, thin, and cost
effective wall or ceiling panel.
Problem
Budget constraints and available surface depth for acoustical
applications may prevent owners from using RPG®’s traditional
number theory diffusors in their rooms, thus denying them the
opportunity to realize the significant benefits of sound diffusion
technology.
Solution
To overcome these problems, RPG® developed the first economical
flat diffusor called the Flatffusor™. This new diffusor
differs from the reflection phase grating (RPG) diffusors pioneered
by RPG® 15 years ago. Traditional RPG® diffusors vary
the phase of the incoming sound by reflection from 1 dimensional
wells or 2 dimensional phase blocks whose depths are based on
number theory sequences. The Flatffusor™ offers sound diffusion
by varying the amplitude of the incident sound rather than the
phase, forming a variable impedance, binary amplitude grating.
An optimal 2 dimensional binary sequence is used to determine
the spatial positions of absorptive and reflective areas. The
absorptive areas are represented by a 0 and the reflective areas
by a 1. The sizes of the binary elements are less than half a
wavelength of the upper frequency limit. The Flatffusor™
is designed to provide uniform diffusion between 1 and 16 kHz.
This mechanism is an effective new innovation in offering sound
diffusion from a flat surface.
The Flatffusor™ looks very much like a fabric wrapped absorptive
panel, yet it provides an attractive alternative to RPG®’s
furniture grade or molded diffusors.
Angular Scattering Response
For normally incident sound, the graph illustrates the angular
response at 12.5 kHz. The flat reflector scatters sound primarily
into the 90° specular direction. The wall mounted absorptive
panel has similar response, only attenuated. The Flatffusor™
panel decreases specular scattering and more closely approaches
the uniform ideal diffusion line.
Diffusion
The performance of a scattering surface is characterized by the
diffusion coefficient, which is the standard deviation of the
1/3 octave angular response, shown here at 12.5 kHz for normal
incidence. The graph illustrates how uniformly the Flatffusor™
scatters across the frequency spectrum, averaged over all incident
angles, compared to a reflective panel.
Installation
Installation of the Flatffusor™ panel is quick and easy.
Simply use construction adhesive or the supplied impaling clips
to mount the panel to walls or ceiling.
Features
Omnidirectional diffusion from a thin, flat binary amplitude grating
Optimal 2 dimensional binary sequence offers uniform diffusion
over a wide frequency range
Acoustical functionality is concealed with an upholstered decorative
fabric
Benefits
Provides high frequency diffusion in the form of a shallow depth
flat panel in situations where space is limited
Offers an alternative to higher priced 1 dimensional and 2 dimensional
broad bandwidth diffusors, which require greater surface depth
Can be used to cover large areas without creating an acoustically
"dead" space
Can be used to provide acoustic gain in conference rooms, classrooms,
and auditoriums to improve speech intelligibility
More product info : http://www.rpginc.com
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