Audio Engineering Society (AES) 119th Convention
New York, 7th-10th of October 2005
Title
Simulation and Visualization of Room Compensation for Wave Field Synthesis with the Functional Transformation Method
Authors
Stefan Petrausch,
Sascha Spors,
and Rudolf Rabenstein
Abstract
Active room compensation based on wave field synthesis (WFS) has been recently introduced.
So far, the verification of the compensation algorithm is only possible through elaborate acoustical measurements.
Therefore, a new simulation method is applied that is based on the functional transformation method (FTM).
Compared with other simulation techniques, the FTM provides several advantages that facilitate the correct simulation of the complete wave field particularly in the interesting frequency ranges for WFS.
The complete procedure, starting from the virtual "measurements" of the acoustical properties of the simulated room, via the correct excitation for the simulated wave field,
towards the resulting animations is presented in this paper.
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Additional Multimedia Content
Several videos can be downloaded in the sequel. All videos were encoded using the DivX-format version 5.
For all simulations measured geometry data and measured physical properties from a real-world room were applied. The room is rectangular and 5.9x6.0m² in size.
The reflection coefficient of the walls is 0.8. The wave field synthesis system was actuated to reproduce a band-limited impulse as a plane wave within the circular loudspeaker array.
The first two videos illustrate the difference of wave field synthesis with (right video) and without (left video) active room compensation.
Furthermore simulations with slightly changed physical properties were carried out, to demonstrate the need for adaptive algorithms.
The left one from the two following videos illustrates the effect of a temperature change of 5°C with non-adaptive room compensation.
The increase in speed of sound causes a time mismatch of the active room compensation system, resulting in undesired reflections inside the loudspeaker array.
The right video illustrates the effect of obstacles in the room, e.g. humans. The reflection factor of the obstacle was set to 0.4, a realistic value for human beings.
Although the obstacle is not located inside the loudspeaker array, strong artefacts for fixed room compensation algorithms can be observed.
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