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Master-Vortrag: Performance Evaluation of Sound Field Translation Methods for Recorded Virtual Reality

Nora Pöhlau
Mittwoch, 30. März 2022

10:00 Uhr
virtueller Konferenzraum

The Higher-Order Ambisonics (HOA) format allows directional recording and playback of sound, making it an attractive tool for spatial audio or immersive sound applications. Because Higher-Order Ambisonics are mathematically based on Spherical Harmonics (SHs), they offer full rotational freedom for the listener (3DoF). However, the sound field can only be correctly reconstructed in a small area around the original recording position due to physical constraints. Three algorithms developed at the Institute for Communications Systems (IKS) make it possible to allow an additional translational movement of the user, even beyond the sweet spot. These algorithms deviate from the physically correct reconstruction in favour of an acoustically plausible playback.

In this thesis, the three algorithms of Space Warping (SW), Adaptive
Space Warping (ASW) and Adaptive Beamforming (ABF) are perceptually compared by conducting multiple listening tests. ABF and ASW split the sound signal into a primary and an ambient part and apply the translation operation only to the primary part. In two web-based listening tests, it was found that this separation is an acoustically valid approach. It was not distinguishable for the listeners if the primary part contained only direct sound or additional early reflexions. In a second step, a listening test in the laboratory was conducted. Here, the algorithms were compared for different translation distances. For small distances, ABF showed the best performance of all algorithms. ABF introduced fluctuating residual
noise for higher distances but still obtained the highest source position ratings. Besides that, a newly proposed variant of SW has proven to perform surprisingly well and scored second best in all ratings behind ABF.