dc.contributor.author	Bau, David
dc.contributor.author	Arend, Johannes M.
dc.contributor.author	Pörschmann, Christoph
dc.date.accessioned	2022-11-28T14:52:08Z
dc.date.available	2022-11-28T14:52:08Z
dc.date.issued	2022-09-30
dc.date.updated	2022-11-10T12:55:51Z
dc.description.abstract	Conventional individual head-related transfer function (HRTF) measurements are demanding in terms of measurement time and equipment. For more flexibility, free body movement (FBM) measurement systems provide an easy-to-use way to measure full-spherical HRTF datasets with less effort. However, having no fixed measurement installation implies that the HRTFs are not sampled on a predefined regular grid but rely on the individual movements of the subject. Furthermore, depending on the measurement effort, a rather small number of measurements can be expected, ranging, for example, from 50 to 150 sampling points. Spherical harmonics (SH) interpolation has been extensively studied recently as one method to obtain full-spherical datasets from such sparse measurements, but previous studies primarily focused on regular full-spherical sampling grids. For irregular grids, it remains unclear up to which spatial order meaningful SH coefficients can be calculated and how the resulting interpolation error compares to regular grids. This study investigates SH interpolation of selected irregular grids obtained from HRTF measurements with an FBM system. Intending to derive general constraints for SH interpolation of irregular grids, the study analyzes how the variation of the SH order affects the interpolation results. Moreover, the study demonstrates the importance of Tikhonov regularization for SH interpolation, which is popular for solving ill-posed numerical problems associated with such irregular grids. As a key result, the study shows that the optimal SH order that minimizes the interpolation error depends mainly on the grid and the regularization strength but is almost independent of the selected HRTF set. Based on these results, the study proposes to determine the optimal SH order by minimizing the interpolation error of a reference HRTF set sampled on the sparse and irregular FBM grid. Finally, the study verifies the proposed method for estimating the optimal SH order by comparing interpolation results of irregular and equivalent regular grids, showing that the differences are small when the SH interpolation is optimally parameterized.
dc.identifier.eissn	2673-8198
dc.identifier.uri	https://depositonce.tu-berlin.de/handle/11303/17737
dc.identifier.uri	https://doi.org/10.14279/depositonce-16523
dc.language.iso	en
dc.rights.uri	http://creativecommons.org/licenses/by/4.0/
dc.subject.ddc	004 Datenverarbeitung; Informatik	de
dc.subject.other	HRTF
dc.subject.other	head-related transfer function
dc.subject.other	spherical harmonics
dc.subject.other	interpolation
dc.subject.other	spatial audio
dc.subject.other	irregular sampling
dc.subject.other	individual HRTFs
dc.title	Estimation of the Optimal Spherical Harmonics Order for the Interpolation of Head-Related Transfer Functions Sampled on Sparse Irregular Grids
dc.type	Article
dc.type.version	publishedVersion
dcterms.bibliographicCitation.articlenumber	884541
dcterms.bibliographicCitation.doi	10.3389/frsip.2022.884541
dcterms.bibliographicCitation.journaltitle	Frontiers in Signal Processing
dcterms.bibliographicCitation.originalpublishername	Frontiers
dcterms.bibliographicCitation.originalpublisherplace	Lausanne
dcterms.bibliographicCitation.volume	2
tub.accessrights.dnb	free
tub.affiliation	Fak. 1 Geistes- und Bildungswissenschaften::Inst. Sprache und Kommunikation::FG Audiokommunikation
tub.publisher.universityorinstitution	Technische Universität Berlin

Estimation of the Optimal Spherical Harmonics Order for the Interpolation of Head-Related Transfer Functions Sampled on Sparse Irregular Grids

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