At the moment there are two working groups involved in establishing methods to measure and characterize scattering surfaces. The AES Working Group SC-04-02, chaired by Dr. Peter D'Antonio and vice-chair Dr. Trevor Cox, is proposing a method to determine the uniform diffusion coefficient. This coefficient, which is bound between zero and one, is derived from the circular autocorrelation of the 1/3-octave angular responses. The diffusion coefficient can be used to evaluate potential diffusing surfaces.
| Diffusion Coefficient | ||
| Hz | QRD® 734 | Reflector |
| 125 | 0.71 | 0.67 |
| 160 | 0.71 | 0.66 |
| 200 | 0.73 | 0.68 |
| 250 | 0.73 | 0.70 |
| 315 | 0.64 | 0.70 |
| 400 | 0.77 | 0.68 |
| 500 | 0.88 | 0.70 |
| 625 | 0.83 | 0.68 |
| 800 | 0.81 | 0.64 |
| 1000 | 0.80 | 0.59 |
| 1250 | 0.70 | 0.47 |
| 1600 | 0.69 | 0.42 |
| 2000 | 0.69 | 0.42 |
| 2500 | 0.68 | 0.41 |
| 3150 | 0.62 | 0.35 |
| 4000 | 0.56 | 0.31 |
RPG
is a member of the Working Group ISO/TC 43/SC 2/WG 25, chaired by Dr.
Jens Rindel, to study a method to evaluate the random incidence scattering
coefficient, used in computer modeling programs. The ISO 17497-1 standard
has been recently published and work continues. The scattering
coefficient is obtained by a comparison of the reverberation times,
obtained from phase-locked average integrated impulse responses, for a
stationary and rotating sample in a reverberation chamber.
| Scattering Coefficient | ||
| Hz |  |
 |
| 125 | 0.06 | 0.00 |
| 162.5 | 0.04 | 0.04 |
| 200 | 0.16 | 0.11 |
| 250 | 0.15 | 0.06 |
| 312.5 | 0.39 | 0.18 |
| 400 | 0.42 | 0.26 |
| 500 | 0.45 | 0.21 |
| 625 | 0.68 | 0.21 |
| 787.5 | 0.91 | 0.22 |
| 1000 | 0.95 | 0.21 |
| 1250 | 0.83 | 0.22 |
| 1562.5 | 0.99 | 0.23 |
| 2000 | 0.88 | 0.16 |
| 2500 | 0.89 | 0.21 |
| 3125 | 1.06 | 0.24 |
| 4000 | 0.91 | 0.39 |
Diffusion and Scattering Coefficients
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Copyright
2000, RPG Diffusor Systems, Inc. |