An alternative coefficient for sound absorption

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Abstract

The acoustic absorption coefficient is a number that indicates which fraction of the incident acoustic power impinging on a surface is being absorbed. The incident acoustic power is obtained by spatial integration of the incident intensity, which is (classically) defined as the time-averaged intensity associated with the incident sound field. The measurement of the effective, in situ, sound absorption coefficient is problematic as the determination thus requires a decomposition of the sound field in an incident and reflected field which, generally, is virtually impossible to do. This paper introduces an alternative coefficient with which the effective acoustic absorption can be expressed. This coefficient is based on an alternative definition of the incident intensity; the time average of the positive values of the instantaneous intensity. The alternative coefficient is much easier to use in a sense that it follows directly from an in situ, instantaneous intensity measurement. The coefficient does not rely on any assumptions other than the assumption that the linearized wave equation is satisfied (and thus the acoustic energy corollary). As a result, one does not need to decompose the sound field in incident and reflected waves. Hence, one does not need to have prior information about the incident sound field. Accordingly, one does not need to have prior information about the source. The coefficient can be determined in any sound field, either transient or stationary, free field and diffuse/(semi-) reverberant sound fields. The alternative coefficient is illustrated by means of several numerical examples.
Original languageEnglish
Title of host publicationInternational Conference on Noise and Vibration Engineering 2012 (ISMA 2012)
EditorsP Sas, S. Jonckheere, D. Moens
Place of PublicationLeuven, Belgium
PublisherKatholieke Universiteit Leuven
Pages85-94
ISBN (Print)978-1-62276-825-7
Publication statusPublished - 17 Sep 2013
Event25th International Conference on Noise and Vibration Engineering, ISMA 2012 - Leuven, Belgium
Duration: 17 Sep 201219 Sep 2012
Conference number: 25
http://past.isma-isaac.be/isma2012

Publication series

Name
PublisherKU Leuven

Conference

Conference25th International Conference on Noise and Vibration Engineering, ISMA 2012
Abbreviated titleISMA
CountryBelgium
CityLeuven
Period17/09/1219/09/12
Internet address

Fingerprint

sound transmission
sound fields
coefficients
acoustics
absorptivity
reflected waves
wave equations
decomposition

Keywords

  • IR-101617
  • METIS-278445

Cite this

Wijnant, Y. H., Kuipers, E. R., & de Boer, A. (2013). An alternative coefficient for sound absorption. In P. Sas, S. Jonckheere, & D. Moens (Eds.), International Conference on Noise and Vibration Engineering 2012 (ISMA 2012) (pp. 85-94). Leuven, Belgium: Katholieke Universiteit Leuven.
Wijnant, Ysbrand H. ; Kuipers, E.R. ; de Boer, Andries. / An alternative coefficient for sound absorption. International Conference on Noise and Vibration Engineering 2012 (ISMA 2012). editor / P Sas ; S. Jonckheere ; D. Moens. Leuven, Belgium : Katholieke Universiteit Leuven, 2013. pp. 85-94
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abstract = "The acoustic absorption coefficient is a number that indicates which fraction of the incident acoustic power impinging on a surface is being absorbed. The incident acoustic power is obtained by spatial integration of the incident intensity, which is (classically) defined as the time-averaged intensity associated with the incident sound field. The measurement of the effective, in situ, sound absorption coefficient is problematic as the determination thus requires a decomposition of the sound field in an incident and reflected field which, generally, is virtually impossible to do. This paper introduces an alternative coefficient with which the effective acoustic absorption can be expressed. This coefficient is based on an alternative definition of the incident intensity; the time average of the positive values of the instantaneous intensity. The alternative coefficient is much easier to use in a sense that it follows directly from an in situ, instantaneous intensity measurement. The coefficient does not rely on any assumptions other than the assumption that the linearized wave equation is satisfied (and thus the acoustic energy corollary). As a result, one does not need to decompose the sound field in incident and reflected waves. Hence, one does not need to have prior information about the incident sound field. Accordingly, one does not need to have prior information about the source. The coefficient can be determined in any sound field, either transient or stationary, free field and diffuse/(semi-) reverberant sound fields. The alternative coefficient is illustrated by means of several numerical examples.",
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Wijnant, YH, Kuipers, ER & de Boer, A 2013, An alternative coefficient for sound absorption. in P Sas, S Jonckheere & D Moens (eds), International Conference on Noise and Vibration Engineering 2012 (ISMA 2012). Katholieke Universiteit Leuven, Leuven, Belgium, pp. 85-94, 25th International Conference on Noise and Vibration Engineering, ISMA 2012, Leuven, Belgium, 17/09/12.

An alternative coefficient for sound absorption. / Wijnant, Ysbrand H.; Kuipers, E.R.; de Boer, Andries.

International Conference on Noise and Vibration Engineering 2012 (ISMA 2012). ed. / P Sas; S. Jonckheere; D. Moens. Leuven, Belgium : Katholieke Universiteit Leuven, 2013. p. 85-94.

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

TY - GEN

T1 - An alternative coefficient for sound absorption

AU - Wijnant, Ysbrand H.

AU - Kuipers, E.R.

AU - de Boer, Andries

PY - 2013/9/17

Y1 - 2013/9/17

N2 - The acoustic absorption coefficient is a number that indicates which fraction of the incident acoustic power impinging on a surface is being absorbed. The incident acoustic power is obtained by spatial integration of the incident intensity, which is (classically) defined as the time-averaged intensity associated with the incident sound field. The measurement of the effective, in situ, sound absorption coefficient is problematic as the determination thus requires a decomposition of the sound field in an incident and reflected field which, generally, is virtually impossible to do. This paper introduces an alternative coefficient with which the effective acoustic absorption can be expressed. This coefficient is based on an alternative definition of the incident intensity; the time average of the positive values of the instantaneous intensity. The alternative coefficient is much easier to use in a sense that it follows directly from an in situ, instantaneous intensity measurement. The coefficient does not rely on any assumptions other than the assumption that the linearized wave equation is satisfied (and thus the acoustic energy corollary). As a result, one does not need to decompose the sound field in incident and reflected waves. Hence, one does not need to have prior information about the incident sound field. Accordingly, one does not need to have prior information about the source. The coefficient can be determined in any sound field, either transient or stationary, free field and diffuse/(semi-) reverberant sound fields. The alternative coefficient is illustrated by means of several numerical examples.

AB - The acoustic absorption coefficient is a number that indicates which fraction of the incident acoustic power impinging on a surface is being absorbed. The incident acoustic power is obtained by spatial integration of the incident intensity, which is (classically) defined as the time-averaged intensity associated with the incident sound field. The measurement of the effective, in situ, sound absorption coefficient is problematic as the determination thus requires a decomposition of the sound field in an incident and reflected field which, generally, is virtually impossible to do. This paper introduces an alternative coefficient with which the effective acoustic absorption can be expressed. This coefficient is based on an alternative definition of the incident intensity; the time average of the positive values of the instantaneous intensity. The alternative coefficient is much easier to use in a sense that it follows directly from an in situ, instantaneous intensity measurement. The coefficient does not rely on any assumptions other than the assumption that the linearized wave equation is satisfied (and thus the acoustic energy corollary). As a result, one does not need to decompose the sound field in incident and reflected waves. Hence, one does not need to have prior information about the incident sound field. Accordingly, one does not need to have prior information about the source. The coefficient can be determined in any sound field, either transient or stationary, free field and diffuse/(semi-) reverberant sound fields. The alternative coefficient is illustrated by means of several numerical examples.

KW - IR-101617

KW - METIS-278445

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SN - 978-1-62276-825-7

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EP - 94

BT - International Conference on Noise and Vibration Engineering 2012 (ISMA 2012)

A2 - Sas, P

A2 - Jonckheere, S.

A2 - Moens, D.

PB - Katholieke Universiteit Leuven

CY - Leuven, Belgium

ER -

Wijnant YH, Kuipers ER, de Boer A. An alternative coefficient for sound absorption. In Sas P, Jonckheere S, Moens D, editors, International Conference on Noise and Vibration Engineering 2012 (ISMA 2012). Leuven, Belgium: Katholieke Universiteit Leuven. 2013. p. 85-94