A method for measuring the angle-dependent absorption coefficient and surface impedance in situ

Melanie Nolan, Erling Nilsson

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

A method is proposed for measuring the angle-dependent surface impedance and absorption coefficient of a boundary material in situ. The method consists in expressing the sound field measured in the vicinity of the boundary as a superposition of plane waves travelling in all directions (i.e., using a spatial Fourier transform). The incident and reflected wave components at the boundary’s surface are separated in the wavenumber domain, from which sound pressure, normal particle velocity, and surface impedance are reconstructed for each angle of incidence. In sufficiently reverberant environments, the angle-dependent properties of the
boundary can be obtained for all angles of incidence simultaneously from a single set of measurements (one source position). Experiments are conducted in a reverberation chamber and in the mock-up of a classroom using a programmable robotic arm to scan the sound field in a three-dimensional domain in the vicinity of the boundary. The derived absorption properties are compared with theoretical values calculated from a Transfer Matrix Model (TMM), showing good agreement up to grazing incidence.
Original languageEnglish
Title of host publicationProceedings of Inter-noise 2020
Number of pages10
Publication date2020
Publication statusPublished - 2020
Event49th International Congress and Exposition on Noise Control Engineering - Virtual event, Seoul, Korea, Republic of
Duration: 23 Aug 202026 Aug 2020
https://internoise2020.org/

Conference

Conference49th International Congress and Exposition on Noise Control Engineering
LocationVirtual event
CountryKorea, Republic of
CitySeoul
Period23/08/202026/08/2020
Internet address

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