Geometric acoustic models have a lower computational complexity than wave-based methods due to the assumption that sound propagates as rays, however this fails to consider the wave-like properties of sound such as diffraction. Historically, tthe Biot-Tolstoy-Medwin (BTM) model and the Uniform Theory of Diffraction (UTD) have been used to augment geometric acoustic models with diffraction. Computational efficiency is essential for real-time application and recently two more efficient models, the Volumetric Diffraction and Transmission (VDaT) model and an infinite impulse response filter (IIR) approximation, were proposed to approximate these solutions. A higher-order IIR filter approximation is proposed in this paper. An experiment is carried out to evaluate the perceived naturalness of these approximations compared to the more accurate analytical solutions. Stationary and moving receivers were considered in simple geometries with a single edge. The results suggest that the higher order IIR approximation is perceptually similar to the BTM model. VDaT and the low order IIR approximation were found to be less natural in some cases. While in dynamic scenes, VDaT was found to be significantly more natural than the other models. The experiment was limited in scope by the simplicity of the scenes considered, however the results suggest the models are perceptually similar. Improvements to the higher-order IIR approximation are suggested and a recommendation is made for future perceptual evaluations.
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