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Extending the closed-form image source model for source directivity (Digital appendix)

Erbes, Vera; Brinkmann, Fabian

The image source model (ISM) is a widespread tool in geometrical room acoustic simulation for the generation of early reflections, which can take into account the source and receiver directivity, as well as the absorption properties of the acoustic environment. A downside of the ISM is the increase in computational effort with increasing image source order caused by costly visibility checks that need to be done separately for each image source. In the special case of a shoebox-shaped, rectangular room, a closed-form ISM exists, thus eliminating the need for visibility checks. However, the closed-form ISM inherently assumes omnidirectional sources, an assumption that is violated in almost all real-life scenarios. In the current study, the closed-form ISM is extended for the source directivity by exploiting geometrical properties of the room. Examples for naturally sounding auralizations from a closed-form ISM combined with a stochastic model for the late reflections are given in the digital appendix, thus making this an appealing approach for applications that require perceptually plausible and computationally efficient simulations rather than high physical accuracy.
  • References: Fabian Brinkmann, Vera Erbes, and Stefan Weinzierl, "Extending the closed-form image source model for source directivity." Fortschritte der Akustik - DAGA 2018, March, Munich, Germany.