FlutterFree by RPG

The First Absorption Phase Grating 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 seem psychoacoustically smaller and reduces the support of acoustic speech levels which makes conversation difficult. FlutterFree by RPG 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. Enter FlutterFree by RPG.

Problem
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 unfortunate side effect of making the room too “dead”.

Solution
FlutterFree by RPG is the first 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.

Absorption
FlutterfreeWhen FlutterFree by RPG panels are mounted 1/16″ apart, the graph can be used to determine the spacing from the mounting wall for the desired absorption frequency. For example, to achieve bass absorption at 100 Hz, follow the vertical 100 Hz frequency line until it intersects the leftward sloping fractional open area line. Follow the horizontal line to the 8″ intersection point.

Diffusion
FlutterfreeThe graph illustrates how FlutterFree® provides useful diffusion above the diffraction limit of roughly 3400 Hz compared to a flat reflective surface. The chart represents the mean diffusion coefficient, which is the normalized standard deviation of the 1/3 octave polar responses for angles of incidence between 0° and 90°.

FlutterFree by RPG Installation

FlutterFree by RPG 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 orders. FlutterFree® can either be nailed or glued directly to a wall surface or mounted with a rear air cavity for low frequency 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 suggested.