Acquisition of bi-directional reflectance functions by Nearfield Acoustical Holography – a preliminary study

Hargreaves, JA

Abstract

It is well known that material absorption and scattering is dependent on incidence and observation angle. Despite this, the corresponding standardised coefficients, which are used to represent these mechanisms within computational acoustic models, aggregate all such dependency into single random-incidence parameters. This limits the accuracy that can be achieved with computational acoustic models – even if these algorithms were to capture the wave physics perfectly, which they often do not, the results would not match physical reality because the input data is too low resolution. Bi-Directional Reflectance Functions are an established way of describing boundary absorption and scattering in computer graphics that have been suggested for use in acoustics. To date, several algorithms have been published that do or could use these in simulation, but no measurement methods are available to acquire them. There is also ambiguity over some aspects of their definition e.g. whether finite panel size is included as a scattering mechanism. This paper adopts a definition suitable for high-frequency Boundary Element Method algorithms that use oscillatory basis functions to capture wave directions. It then proposes an acquisition method based on double-layer Near-Field Acoustical Holography and assesses it accuracy using 2D simulations.

Citation

Hargreaves, J. Acquisition of bi-directional reflectance functions by Nearfield Acoustical Holography – a preliminary study. Presented at International Congress on Acoustics 2019, Aachen

• Presentation Conference Type: Lecture
• Conference Name: International Congress on Acoustics 2019
• Conference Location: Aachen
• End Date: Sep 13, 2019
• Publication Date: Sep 14, 2019
• Deposit Date: Sep 3, 2019
• Publicly Available Date: Sep 3, 2019
• Book Title: Proceedings of the ICA 2019 AND EAA EUROREGIO 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019
• ISBN: 9783939296157
• Publisher URL: http://pub.dega-akustik.de/ICA2019/data/articles/000454.pdf
• Related Public URLs: http://www.ica2019.org/
• Additional Information: Event Type : Conference