Estimating viscous losses in recycled granular microparticles : a time-domain wave decomposition impedance tube with boundary condition approximation

Železnik, Anže (author), Čurović, Luka (author), Murovec, Jure (author), Cerkovnik, Nejc (author), Prezelj, Jurij (author)

The sound absorption coefficient of a material represents the fraction of acoustic energy not reflected from its surface. The absorption is influenced by viscous losses in porous structures and sample resonances. This study proposes a novel method for measuring absorption coefficients in extended impedance tubes, specifically designed to distinguish between viscous losses and resonances, but can also be used to estimate the sound absorption coefficient in a standard impedance tube. The method is based on a time-domain wave decomposition for its simplicity of use and ability to visualize sound impulse reflections, revealing reflections of sound within the sample. A long vertical impedance tube was used to achieve sufficient separation of the sound impulses. Random noise was used as the excitation signal and spectral division deconvolution was used to calculate the sound wave impulses in the impedance tube. The proposed method was validated against the transfer function method using samples of rock wool, reconstituted foam, and polyether foam. The advantage of the proposed method was demonstrated on measurements of several granular fractions of recycled silica sand to determine the granule sizes where the main mechanism of sound absorption is viscous losses as opposed to resonances. It was found that the sound absorption caused by viscous losses is greatest for granule diameters around 500 μm.

• Language: English
• Keywords: absorption coefficient, impedance tubes, time-domain wave decomposition, deconvolution, granular materials
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 11 str.
• Numbering: Vol. 228, [art. no.] 110372
• PID: 20.500.12556/RUL-164583
• UDC: 534/535
• ISSN on article: 0003-682X
• DOI: 10.1016/j.apacoust.2024.110372
• COBISS.SI-ID: 213564419
• Publication date in RUL: 04.11.2024

Record is a part of a journal

• Title: Applied acoustics
• Shortened title: Appl. Acoust.
• Publisher: Elsevier Science
• ISSN: 0003-682X
• COBISS.SI-ID: 24982016

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: koeficient absorpcije, impedančne cevi, valovna dekompozicija v časovni domeni, dekonvolucija, granulirani materiali

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0401 (B)
• Name: Energy engineering