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On variation of absorption factor due to measurement method and correction factors for conversion between methods
KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strömningsakustik. Acoustics department, Scania CV AB, Södertälje, Sweden.ORCID-id: 0000-0003-1604-8263
KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. Acoustics department, Scania CV AB, Södertälje, Sweden.ORCID-id: 0000-0002-3826-3055
KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.ORCID-id: 0000-0003-4103-0129
2012 (Engelska)Ingår i: 41st International Congress and Exposition on Noise Control Engineering 2012, INTER-NOISE 2012, Volume 11, 2012, Institute of noise control engineering , 2012, s. 9343-9350Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
Abstract [en]

Sound absorbing materials are used in many applications to reduce sound, and their soundabsorbing characteristics are most often determined experimentally since theoreticaldetermination is difficult. Sound absorption factors are used in material specifications aswell as input to numerical simulations.Several methods for experimental determination of the absorption factor exist, two of themstandardized and frequently used. It is commonly known that the absorption factorobtained by these two methods differs as different sound fields are prescribed by thestandards. However, the size of the differences has not been so well described. Due to thisdifference, the choice of method is critical in order to avoid errors in simulations andspecifications of material properties.Experimental determination of absorption factors for three commonly used absorbers wasperformed, resulting in significant differences between the two methods. Correction factorsto compensate the absorption factor determined at one acoustic state and used in anotherare given. Theory verifying the differences is also presented.

Ort, förlag, år, upplaga, sidor
Institute of noise control engineering , 2012. s. 9343-9350
Nyckelord [en]
Sound absorption coefficient, measurements
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
URN: urn:nbn:se:kth:diva-128557Scopus ID: 2-s2.0-84883591764ISBN: 978-162748560-9 (tryckt)OAI: oai:DiVA.org:kth-128557DiVA, id: diva2:648077
Konferens
41st International Congress and Exposition on Noise Control Engineering 2012, INTER-NOISE 2012, New York, NY; United States; 19 August 2012 through 22 August 2012
Anmärkning

References: Färm, A., Boij, S., Glav, R., On sound absorbing characteristics and suitable measurement methods (2012) Proceedings of the 7 International Styrian Noise, Vibration and Harshness Congress; (2003) Acoustics - Measurement of Sound Absorption in a Reverberation Room, , ISO 354; (1996) Acoustics - Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes - Part 1: Method Using Standing Wave Ratio, , International standard ISO 10534-1; Delany, M.E., Bazley, E.N., Acoustic properties of fibrous absorbent materials (1970) Applied Acoustics, 3, pp. 105-116; Corcos, G.M., The structure of the turbulent pressure field in boundary layer flows J. of Fluid Mechanics, 18, p. 1964; Biot, M.A., Generalized theory of acoustic propagation in porous dissipative media (1962) Journal of the Acoustical Society of America, 34 (9), pp. 1254-1264; Attenborough, K., Acoustical characterization of porous materials (1982) Physics Reports, 82 (3), pp. 179-227; Sastry, J.S., Munjal, M.L., A transfer matrix approach for evaluation of the response of a multi-layer infinite plate to a two-dimensional pressure excitation (1995) Journal of Sound and Vibration, 182 (1), pp. 109-128

QC 20130913

Tillgänglig från: 2013-09-13 Skapad: 2013-09-13 Senast uppdaterad: 2016-02-15Bibliografiskt granskad
Ingår i avhandling
1. Analysis of Acoustic Absorption with Extended Liner Reaction and Grazing Flow
Öppna denna publikation i ny flik eller fönster >>Analysis of Acoustic Absorption with Extended Liner Reaction and Grazing Flow
2013 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Acoustic absorbing liners are efficient and commonly used measures to reduce sound levels in many fields of application. The sound reducingperformance of the liners is dependent on the acoustic state, defined by e.g. the flow and sound field interacting with the liner. To enable liner optimization the impact of these factors on the liner performance must be predictable. Studies of the impact of these factors were performed with existing experimental, analytical and numerical methods at low Mach number flows and material used in truck engine compartments. The study showed significant impact of both flow and sound field onthe liner performance. The size of the impact of the flow depends on which of the existing methods and models that was used, implying theneed of complementary methods. A new numerical method to model the boundary layer effect was for this reason developed in this work. The method was shown to predict the impact of flow correctly compared to the Pridmore-Brown solution and the method was computationally efficient. The sound reducing performance of a liner exposed to complex sound field and grazing flow can be predicted using existing methods together with the new proposed method. Extra care has to be taken when bulk reacting liners are considered since additional complications compared to locally reacting surfaces occur in presence the of grazing flow.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2013. s. x, 46
Serie
Trita-AVE, ISSN 1651-7660 ; 2013:42
Nyckelord
Sound absorption, acoustic lining, non-locally reacting, boundary layer, grazing flow, sound field, transfer matrix method
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:kth:diva-128711 (URN)
Presentation
2013-09-27, K2, Teknikringen 28, KTH, Stockholm, 13:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20130916

Tillgänglig från: 2013-09-16 Skapad: 2013-09-16 Senast uppdaterad: 2013-09-16Bibliografiskt granskad

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Färm, AnnaGlav, RagnarBoij, Susann

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