Determination of boundary conditions by inverse modeling of room acoustics

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Room acoustic simulation algorithms and auralization tools are based on several simplifications concerning the room geometry, the reflection and scattering properties and the wave effects such as diffraction and modes. Previous studies and ongoing research have shown that these simplifications can be considered inaudible, if certain procedures are followed. All those guidelines, however, depend on the Implementation, on the room example chosen and on the signal used for auralization. Apart from physically-based simulation, perceptual culling based on simultaneous masking allows control of auralization strategies for keeping the performance in the limits of real-time processing. It is not yet known quantitatively, how the simulation parameters influence the perception of room acoustics In its various dimensions (loudness, timbre, spaciousness, clarity, etc.). Simulation parameters in this respect are: degree of details in the CAD room model, the uncertainty in absorption and scattering models, the transition order from early exact specular to statistic reflection models in temporal and spatial resolution, the implementation ("dialect") of late reverberation (radiosity, diffuse rain, shaped noise) and its statistical parameters (number of particles, patch sizes, etc.), the role of uncertainty of HRTF databases and source recording techniques.Previous work of the applicant was focused on hybrid geometric modeling, better surface modelling, hybrid geometric-wave modeling and round robin tests. Actual research projects are focused on real-time Implementation and studies of interactive VR systems and on CAD modelling of large rooms. The approach In this Research Unit is the logical continuation of previous work. Previous work also included preliminary studies of the parameters In reverberation filter design These studies showed that AFC based listening test strategies are well qualified to measure audibility thresholds of simulation artifacts by means of psychometric functions. Nevertheless the test conditions (only audio, audio and vision, audio and vision and task) and the psychoacoustic test in its reproduction quality and test subject selection and instruction Is a crucial part of the project. The goal of this subproject Is to determine the perceptual detection ability and differentiability, with respect to the simulation parameters and their limits in spatial and temporal domains. Existing algorithms that have been developed by the applicant should be applied and tested with psycho-acoustically approved methods, to ascertain perceptual thresholds regarding various dimensions of room acoustics perception and the impact of environmental simulation parameters.