A priori mesh grading for the numerical calculation of the head-related transfer functions

Abstract

Head-related transfer functions (HRTFs) describe the directional filtering of the incoming sound caused by the morphology of a listener's head and pinnae. When an accurate model of a listener's morphology exists, HRTFs can be calculated numerically with the boundary element method (BEM). However, the general recommendation to model the head and pinnae with at least six elements per wavelength renders the BEM as a time-consuming procedure when calculating HRTFs for the full audible frequency range. In this study, a mesh preprocessing algorithm is proposed, viz., a priori mesh grading, which reduces the computational costs in the HRTF calculation process significantly. The mesh grading algorithm deliberately violates the recommendation of at least six elements per wavelength in certain regions of the head and pinnae and varies the size of elements gradually according to an a priori defined grading function. The evaluation of the algorithm involved HRTFs calculated for various geometric objects including meshes of three human listeners and various grading functions. The numerical accuracy and the predicted sound-localization performance of calculated HRTFs were analyzed. A-priori mesh grading appeared to be suitable for the numerical calculation of HRTFs in the full audible frequency range and outperformed uniform meshes in terms of numerical errors, perception based predictions of sound-localization performance, and computational costs.

Spectral equalization in binaural signals represented by order-truncated spherical harmonics

“…To assess the generalizability to other HRTF catalogs, SHF and HRF filters were calculated using HRIRs numerically obtained from a head only mesh from the FABIAN head and torso simulator 29 and mesh2HRTF. 30 shown in Fig. 5.…”

Current Use and Future Perspectives of Spatial Audio Technologies in Electronic Travel Aids

“…Recent works introduced the fast multipole method (FMM) and the reciprocity principle (i.e., interchanging sources and receivers) in order to face BEM efficiency issues [140,141]. Ultimately, localization performances of simulated HRTFs through the BEM were found to be similar to those observed with acoustically measured HRTFs [142], and databases of simulated HRTFs [143] as well as open-source tools for calculating HRTFs through the BEM given a head mesh as input [144] are available online.…”

Personalized HRTF Modeling Using DNN-Augmented BEM

“…For numerical simulation, we use the open-source library MESH2HRTF, which is based on a fast-multipole BEM solver [28]. For each subject in the dataset, we run a BEM simulation for each frequency from 100 Hz to 20 kHz in increments of 100 Hz and sample the solution at 440 collocated spatial directions on a 1.47 m shell away from the subject's head center.…”