From absorption to impedance: Enhancing boundary conditions in room acoustic simulations

Boris Mondet*, Jonas Brunskog, Cheol-Ho Jeong, Jens Holger Rindel

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In room acoustic simulations the surface materials are commonly represented with energy parameters, such as the absorption and scattering coefficients, which do not carry phase information. This paper presents a method to transform statistical absorption coefficients into complex surface impedances which are needed for phased or time-domain calculation methods. Two 5-parameter impedance models based on fractional calculus are suggested to achieve a general model for common acoustic materials, thereby ensuring that the impedance found has a physical meaning. The five parameters for the general models are determined by solving an inverse problem with an optimization method. Due to the non-uniqueness of retrieving complex-valued impedances from real-valued absorption coefficients, prior information about the absorber of interest can be used as constraints, which is shown to help determine the impedance more correctly. Known material models, such as Miki’s and Maa’s models, are taken as references to assess the validity of the suggested model. Further stability and sensitivity investigations indicate that the method presented constitutes an efficient solution to convert sound absorption coefficients back to their original complex surface impedances.
Original languageEnglish
Article number106884
JournalApplied Acoustics
Volume157
Number of pages13
ISSN0003-682X
DOIs
Publication statusPublished - 2019

Keywords

  • Inverse problem
  • Surface impedance
  • Absorption coefficient
  • Room acoustics

Cite this

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title = "From absorption to impedance: Enhancing boundary conditions in room acoustic simulations",
abstract = "In room acoustic simulations the surface materials are commonly represented with energy parameters, such as the absorption and scattering coefficients, which do not carry phase information. This paper presents a method to transform statistical absorption coefficients into complex surface impedances which are needed for phased or time-domain calculation methods. Two 5-parameter impedance models based on fractional calculus are suggested to achieve a general model for common acoustic materials, thereby ensuring that the impedance found has a physical meaning. The five parameters for the general models are determined by solving an inverse problem with an optimization method. Due to the non-uniqueness of retrieving complex-valued impedances from real-valued absorption coefficients, prior information about the absorber of interest can be used as constraints, which is shown to help determine the impedance more correctly. Known material models, such as Miki’s and Maa’s models, are taken as references to assess the validity of the suggested model. Further stability and sensitivity investigations indicate that the method presented constitutes an efficient solution to convert sound absorption coefficients back to their original complex surface impedances.",
keywords = "Inverse problem, Surface impedance, Absorption coefficient, Room acoustics",
author = "Boris Mondet and Jonas Brunskog and Cheol-Ho Jeong and Rindel, {Jens Holger}",
year = "2019",
doi = "10.1016/j.apacoust.2019.04.034",
language = "English",
volume = "157",
journal = "Applied Acoustics",
issn = "0003-682X",
publisher = "Pergamon Press",

}

From absorption to impedance: Enhancing boundary conditions in room acoustic simulations. / Mondet, Boris; Brunskog, Jonas; Jeong, Cheol-Ho; Rindel, Jens Holger.

In: Applied Acoustics, Vol. 157, 106884, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - From absorption to impedance: Enhancing boundary conditions in room acoustic simulations

AU - Mondet, Boris

AU - Brunskog, Jonas

AU - Jeong, Cheol-Ho

AU - Rindel, Jens Holger

PY - 2019

Y1 - 2019

N2 - In room acoustic simulations the surface materials are commonly represented with energy parameters, such as the absorption and scattering coefficients, which do not carry phase information. This paper presents a method to transform statistical absorption coefficients into complex surface impedances which are needed for phased or time-domain calculation methods. Two 5-parameter impedance models based on fractional calculus are suggested to achieve a general model for common acoustic materials, thereby ensuring that the impedance found has a physical meaning. The five parameters for the general models are determined by solving an inverse problem with an optimization method. Due to the non-uniqueness of retrieving complex-valued impedances from real-valued absorption coefficients, prior information about the absorber of interest can be used as constraints, which is shown to help determine the impedance more correctly. Known material models, such as Miki’s and Maa’s models, are taken as references to assess the validity of the suggested model. Further stability and sensitivity investigations indicate that the method presented constitutes an efficient solution to convert sound absorption coefficients back to their original complex surface impedances.

AB - In room acoustic simulations the surface materials are commonly represented with energy parameters, such as the absorption and scattering coefficients, which do not carry phase information. This paper presents a method to transform statistical absorption coefficients into complex surface impedances which are needed for phased or time-domain calculation methods. Two 5-parameter impedance models based on fractional calculus are suggested to achieve a general model for common acoustic materials, thereby ensuring that the impedance found has a physical meaning. The five parameters for the general models are determined by solving an inverse problem with an optimization method. Due to the non-uniqueness of retrieving complex-valued impedances from real-valued absorption coefficients, prior information about the absorber of interest can be used as constraints, which is shown to help determine the impedance more correctly. Known material models, such as Miki’s and Maa’s models, are taken as references to assess the validity of the suggested model. Further stability and sensitivity investigations indicate that the method presented constitutes an efficient solution to convert sound absorption coefficients back to their original complex surface impedances.

KW - Inverse problem

KW - Surface impedance

KW - Absorption coefficient

KW - Room acoustics

U2 - 10.1016/j.apacoust.2019.04.034

DO - 10.1016/j.apacoust.2019.04.034

M3 - Journal article

VL - 157

JO - Applied Acoustics

JF - Applied Acoustics

SN - 0003-682X

M1 - 106884

ER -