|
| |
|
Modffusor
The First Modulated Optimized Diffusor
From The Acoustical Industry's Leading Innovator |
In 1983, RPG Diffusor systems, Inc. introduced the first commercial sound diffuser that offered uniform scattering over a designable bandwidth. The QRD has now been used in thousands of project in a wide range of venues. As with any technology, research and experimentation lead to advance. The QRD is a reflection phase grating formed from the periodic repetition of a base shape, consisting of a series of wells of depth based on the quadratic residue sequence, separated by dividers. While periodicity is the basis of the QRD, it is also one of its limitations, because periodicity causes lobing in specific diffraction directions. To minimize this lobing, which compromises the uniformity of the polar response, RPG developed the Modffusor. By contrast to the QRD, the Modffusor is formed from an aperiodic array of a singe, asymmetric, optimized base shape. The optimization offers better performance than a low-prime, number theoretic diffuser and the aperiodic modulation minimizes lobing non-uniformity caused by periodicity. This, the Modffusor offers the next generation of high performance reflection phase gratings.
|
|
|
| Problem and Solution |
Problem
Quadratic Residue Diffusors (QRD) owe their diffusing ability to the phenomenon of diffraction from a periodic reflection phase grating. The product of the number and width of the wells defines the diffraction direction and the energy in these directions is equal due to the fact that the quadradic residue well depth sequence has a flat power spectrum. To cover wide areas, the QRD is repeated. This periodicity decreases uniformity by focusing the energy in the diffraction directions (B), preventing uniform diffusion (c) from being achieved.
Solution
To solve this problem, RPG patented a concept called Aperiodic Modulation of a Singe Asymmetric Base Shape, in which a singe, optimized, asymmetric, base shape (¡®¡¯0¡¯¡¯ unit) is modulated by simply flipping the base unit 180 (forming ¡°1¡±Unit ) according to the prescription of an optimal binary sequence with good aperiodic array below. The base shape, consisting of 7 full wells and two zero-depth half wells on either end, is optimized using RPG¡¯s proprietary Shape Optimizer software. Using aperiodic modulation, the performance of the single optimal base shap can be preserved, while covering an infinite area. The patented half wells provide seamless tilling and pseudo-symmetry which is aesthetically pleasing.
|
 |
"0"Unit¡¡¡¡¡¡¡¡¡¡¡¡"1"Unit |
 |
Performance Specifications |
Frequency, Hz
|
Frequency, Hz
 |
Performance Specifications
Diffusion coefficient comparison between a traditional QRD and the Modffusor, reveals significant performance improvement, due to the reduction of periodic lobing. A flat panel response of comparable size also shown to indicate the Modffusor¡¯s better low frequency diffusion, as indicated by the onset of diffusion.
|
The Modffusor exhibits minimal absorption with a slight rise between 500 and 630 Hz, due to pressure gradient absorption between resonant wells. If a panel fabric is placed over the surface, then this resistive element increases the absorption significantly in this frequency region. |
Installation
Installation of the array is accomplished by mounting the labeled Modffusors sequentially over supplied mounting cleats, which are attached to the wall or ceiling. The array consists of a beginning unit, a series of interior units and an end unit.
|
|
|
