Abstract
Nowadays, wave-based simulations of head-related transfer functions (HRTFs) lack strong justifications to replace HRTF measurements. The main cause is the complex interactions between uncertainties and biases in both simulated and measured HRTFs. This paper deals with the validation of pinna-related high-frequency information in the ipsilateral directions-of-arrival, computed by lossless wave-based simulations with finite-difference models. A simpler yet related problem is given by the pinna-related transfer function (PRTF), which encodes the acoustical effects of only the external ear. Results stress that PRTF measurements are generally highly repeatable but not necessarily easily reproducible, leading to critical issues in terms of reliability for any ground truth condition. On the other hand, PRTF simulations exhibit an increasing uncertainty with frequency and grid-dependent frequency changes, which are here quantified analyzing the benefits in the use of a unique asymptotic solution. In this validation study, the employed finite-difference model accurately and reliably predict the PRTF magnitude mostly within ±1 dB up to ≈8 kHz and a space- and frequency-averaged spectral distortion within about 2 dB up to ≈ 18 kHz.
Highlights
Human perception relies on acoustic information included in the head-related transfer function (HRTF), which accounts for the linear acoustic transformations produced by the listener’s head, pinna, torso, and shoulders.1 Unless adaptation and learning occurs,2 head-related transfer functions (HRTFs) are usually not perceptually transferable3 mainly due to the uniqueness of the human pinna.4,5b)Current address: Hefio Ltd., Otakaari 5 A, 02150 Espoo, Finland. c)ORCID: 0000-0002-0621-2704. d)ORCID: 0000-0002-8261-4596.errors,18 or boundary modelling errors.19,20 their validity in the full audible frequency range has not been yet established using rigorous Verification&Validation (V&V) studies.21,22 The boundary element method23–27 (BEM) and the finite difference time domain16,28,29 (FDTD) methods are the most studied HRTF simulation methods.Broadly, simulation V&V studies aim to measure the magnitude of the involved errors relative to the working definitions and premises/assumptions
A simpler yet related problem is given by the pinna-related transfer function (PRTF), which encodes the acoustical effects of only the external ear
Since quantitative comparisons are usually favored in computational physics69 and to better support the qualitative data in Figs. 5–8, a frequency-dependent16 spectral distortion (SD) is first used as an HRTF comparison metric
Summary
Human perception relies on acoustic information included in the head-related transfer function (HRTF), which accounts for the linear acoustic transformations produced by the listener’s head, pinna, torso, and shoulders. Unless adaptation and learning occurs, HRTFs are usually not perceptually transferable mainly due to the uniqueness of the human pinna.4,5b)Current address: Hefio Ltd., Otakaari 5 A, 02150 Espoo, Finland. c)ORCID: 0000-0002-0621-2704. d)ORCID: 0000-0002-8261-4596.errors, or boundary modelling errors. their validity in the full audible frequency range has not been yet established using rigorous Verification&Validation (V&V) studies. The boundary element method (BEM) and the finite difference time domain (FDTD) methods are the most studied HRTF simulation methods.Broadly, simulation V&V studies aim to measure the magnitude of the involved errors relative to the working definitions and premises/assumptions. Human perception relies on acoustic information included in the head-related transfer function (HRTF), which accounts for the linear acoustic transformations produced by the listener’s head, pinna, torso, and shoulders.. Unless adaptation and learning occurs, HRTFs are usually not perceptually transferable mainly due to the uniqueness of the human pinna.. Their validity in the full audible frequency range has not been yet established using rigorous Verification&Validation (V&V) studies.. The boundary element method (BEM) and the finite difference time domain (FDTD) methods are the most studied HRTF simulation methods. Verification studies aim to quantify the numerical errors contained in a simulated result, while validation aims to measure the adequacy of using the simulated model in predicting the modelled realworld processes
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