FlutterFree ®

FlutterFree ®
1D Diffusion
The First Acoustical Hardwood Molding
From The Acoustical Industry’s Leading Innovator
Absorptive fabric wrapped panels are the traditional treatment for flutter echoes which are
caused by repetitive reflections between hard parallel walls. While absorption reduces flutter
echoes, it also produces an acoustically “dead” space. The resulting lack of ambiance makes the
room feel acoustically smaller and reduces the support of acoustic speech levels which makes
conversation difficult. FlutterFree® is a handsome, furniture grade, acoustical hardwood molding
that provides flutter echo control as well as bass absorption. Its application converts small rooms
with flat parallel surfaces into functional spaces with good speech intelligibility, sound quality,
and a natural, comfortable ambiance. It expands the designer’s flutter control finish treatment
options beyond fabric upholstered surfaces.
The Sound of Innovation™
651-C Commerce Drive, Upper Marlboro, MD, 20774, Phone: 301.249.0044, Fax: 301.249.3912, Email: info@rpginc.com, Internet: www.rpginc.com
Problem and Solution
Repetitive reflections from hard parallel surfaces produce flutter echoes that are perceived as timbre coloration and degrade
sound quality and speech intelligibility. Absorptive surfaces are often used to control this annoying problem, with the side
effect of making the room too acoustically “dead”.
FlutterFree® is the first diffusive acoustical hardwood molding that
controls flutter echo by diffusion, maintaining the natural ambiance of
the room. When adjacent panels are spaced and mounted with an air
cavity, low frequency absorption can also be achieved.
Performance Specifications
Acoustical Data
The graph illustrates the random incidence ISO
354 A-Mount absorption coefficients (red), the
ISO 17497-1 scattering coefficients (green) and
the ISO 17497-2 diffusion coefficients (blue). The
absorption data is presented to the standard
frequency of 5,000 Hz, whereas the scattering
• Furniture grade, hardwood, sound
diffusing acoustical molding
• Low frequency absorption mounting option
• FlutterFree® works on the 1D QRD® reflection
phase grating principle
• Modular extruded diffusive strips
• Handsome furniture grade hardwood finish
offers specifiers a new approach to flutter
echo control that does not rely on the use
of fabric upholstered fiberglass panels
• Offers an almost unlimited variety of
lacquered, stained, or painted finishes
and hardwood options
• Diffusive flutter control minimizes
flutter echoes without making the
space acoustically “dead”
• Diffusive flutter control provides an ambient
environment to support speech in conference
rooms for less fatigue, greater coverage, and
high speech intelligibility
• Mounting FlutterFree® over an air
cavity provides low frequency absorption
to minimize boominess and lack of
definition in small rooms
and diffusion data extend to 20,000 Hz.
Supplemental Absorption Data
The absorption coefficients for slotted and nonslotted FlutterFree® are shown, along with the A
Mount data (red) over the full frequency range.
The non-slotted FlutterFree® planks are backed
with 1” Fiberglass (FG) in a Helmholtz mounting
1/16" apart (C Mount blue), on the surface and
with a 3.5” cavity (D Mount color). The slotted
FlutterFree® planks (inset) are backed with 1”
Fiberglass (FG) and mounted with no space
between the planks, on the surface and with a
3.5” cavity.
Conference and teleconference rooms,
Lecture Halls, Distance Learning Rooms,
Public spaces, Listening rooms, Recording
and broadcast studios, Post production
studios, Home theaters, Rehearsal rooms,
Auditoriums, Performance spaces
• Size: 96” (L) x 3-15/16'' (W) x 1-1/16'' (D)
• Custom lengths are available up to 8’, call for
longer lengths.
• Weight: 1 lb/ft
• Finishing: FlutterFree® can be supplied
unfinished, clear lacquered, stained and
lacquered, and painted
• When field finishing, all exposed surfaces,
including the cut end surfaces, should be
treated to minimize warping
FlutterFree® is molded on a 5 head wood molder from hardwood that is kiln dried to 6-8% moisture content. RPG® takes
every precaution to minimize warping by stress relieving the rear surface and treating all exposed surfaces on prefinished
absorption. In this Helmholtz mounting, a semi rigid fiberglass panel is mounted 1/4" behind the FlutterFree®. To standardize
and maintain the proper spacing, lamello biscuits are included. When used as wall panels, a hardwood frame (not supplied) is
1- 1/16''
orders. FlutterFree® can either be nailed or glued directly to a wall surface or mounted with a rear air cavity for low frequency
3 - 15/16''
FlutterFree® End View
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