RPG Diffusor Systems, Inc., 651-C Commerce Dr., Upper Marlboro, MD 20772
Altec Lansing Corp.
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.