Traditional fabric wrapped panels offer a cost effective, low profile aesthetic approach to providing reflection and reverberation control. However, these panels offer little sound diffusion and large area application may lead to an acoustically "dead" space. Variable impedance arrays offer some help, but cannot provide diffusion at mid and high frequencies.
RPG® developed an innovative variable impedance panel by fabric wrapping a resorptive binary template consisting of reflective areas and holes over a semi rigid fiberglass panel. The resulting Binary Amplitude Diffsorbor™ panel provides mid and high frequency diffusion and low frequency absorption. The picture right shows the BAD template mounted over the fibreglass panel, this mask is laquered to produce a highly decorative product. The panel can be fabric wrapped in any colour the client or architect requires.
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 Binary Amplitude Diffsorbor™: the first flat, zero depth diffusing absorber. A BAD™ Panel simultaneously provides uniform sound diffusion at high and mid band frequencies and crosses over to pure absorption below the diffusive
cut-off. The energy that is not diffused is absorbed.
To accomplish diffsorption, RPG® developed a new planar 2 dimensional binary reflection amplitude grating consisting of a 31 x 33 element array of 1,023 0.5 sq. in. absorptive or reflective areas. The reflective areas (black in illustration to left) 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 is in contrast to RPG®'s reflection phase gratings which use phase variation, rather than amplitude variation, to provide diffusion. The Binary Amplitude Diffsorbor™ (BAD™) Panel 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, 25mm x 25mm panels provide diffusion up to about 1 kHz. Remaining high frequency reflections would still corrupt speech and music quality.
The BAD™ Panel 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 BAD™ Panel extends the acoustical performance of traditional absorptive fabric wrapped panels and allows wide area coverage without excessive deadening. Acousticians now have a diffsorptive alternative to traditional purely absorptive fabric wrapped panels at competitive prices. The BAD™ Panel is ideal for any facility that needs reflection control from a decorative, upholstered, thin, and cost effective wall or ceiling panel.
The graph illustrates how the BAD™ Panel offers an increase in bass absorption over a standard upholstered 25mm panel below 1000 Hz, and a decreased absorption above this frequency for a 15mm diameter and the standard 12mm(approx) diameter hole. The binary template allows the sound above 1000 Hz, which was conventionally lost to absorption, to be uniformly diffused providing reflection control without destroying the room's ambience.
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 above at 12.5 kHz. The graph illustrates how uniformly the BAD™ Panel scatters sound across the frequency spectrum, compared to a reflective panel, for normal incidence.
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 BAD™ Panel decreases specular scattering and more closely approaches the uniform ideal diffusion line.
Installation of the BAD™ Panel is quick and easy. Simply use impaling clips, battens or Rotofast mounts to walls or ceiling. The BAD™ Panel can also be used in any T-bar or similar mounting system.
Features and Benefits
Any acoustically transparent fabric approved by RPG® Diffusor Systems, Inc
6 lb. density fiberglass
Split Batten mounting or flush mount, or mount in a cavity for increased performance
Unit Size Minimum of units is 600mm x 406mm
Units can be made with any height up to 2500mm
Units can be made with any width up to 1200mm
Units can be made with depths between 25mm - 150mm
Units can be made with flat, bevelled, angled, or radius cut edges
Note: All dimensions are allowed a tolerance of ± 2mm due to material shrinkage and variations.
Technical datasheet (PDF)