### ASA 124th Meeting New Orleans 1992 October

## 3aAA6. Evaluating the influence of directional scattering coefficients for
reflection, absorption, and diffusion in the auralization of acoustic designs.

**Peter D'Antonio
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*RPG Diffusor Systems, Inc., 651-C Commerce Dr., Upper Marlboro, MD 20772
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**Akira Mochimaru
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*Altec Lansing Corp.
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Auralization of virtual spaces by convolution of anechoic music with the
room's impulse response, measured from either scale models or calculated for
CAD image or ray-tracing models, is becoming popular as a design diagnostic.
This process requires the use of directional scattering coefficients, as
opposed to random incidence coefficients, to properly account for absorption,
reflection, diffusion, and diffraction at the room's boundaries. Since these
polar coefficients, which take into account the direction and frequency of the
incident sound, observation position and surface area, do not exist in the
acoustical literature, D'Antonio has begun a systematic analysis using a new
polar mapping measurement methodology. This paper describes the measurement
methodology and initial attempts to incorporate them into the Acousta CADD[sup
(registered)] program and evaluate their effect. Implementation of the
directional scattering coefficients involves attenuation of scattered rays as a
function of the angle of incidence, observation and frequency and the
introduction of the appropriate time spread of each surface into the time
response. If computing power permits, the room's impulse response will be
evaluated by convolution of the impulse response of all incident rays,
appropriately delayed and spherically attenuated by the travel path, with the
respective impulse response of each surface. The polar response of each surface
will define the solid angle irradiated and the level will be used to determine
the reflection order.