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Sound attenuation in ducts using locally resonant periodic aluminum patches
KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.ORCID-id: 0000-0002-6069-4636
2016 (engelsk)Inngår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 139, nr 6, s. 3276-3286Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In recent years, the control of low frequency noise has received a lot of attention for several applications. Traditional passive noise control techniques using Helmholtz resonators have size limitations in the low frequency range because of the long wavelength. Promising noise reductions, with flush mounted aluminum patches with no size problems can be obtained using local resonance phenomenon implemented in acoustic metamaterial techniques. The objective of this work is to introduce locally resonant thin aluminum patches flush mounted to a duct walls aiming at creating frequency stop bands in a specific frequency range. Green's function is used within the framework of interface response theory to predict the amount of attenuation of the local resonant patches. The two-port theory and finite elements are also used to predict the acoustic performance of these patches. No flow measurements were conducted and show good agreement with the models. The effect of varying the damping and the masses of the patches are used to expand the stop bandwidth and the effect of both Bragg scattering and the locally resonant mechanisms was demonstrated using mathematical models. The effect of the arrays of patches on the effective dynamic density and bulk modulus has also been investigated.

sted, utgiver, år, opplag, sider
Acoustical Society of America (ASA), 2016. Vol. 139, nr 6, s. 3276-3286
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-192861DOI: 10.1121/1.4948990ISI: 000379164900042Scopus ID: 2-s2.0-84977109960OAI: oai:DiVA.org:kth-192861DiVA, id: diva2:972571
Forskningsfinansiär
EU, FP7, Seventh Framework Programme, 289352
Merknad

QC 20160929

Tilgjengelig fra: 2016-09-21 Laget: 2016-09-21 Sist oppdatert: 2017-11-21bibliografisk kontrollert
Inngår i avhandling
1. Innovative noise control in ducts
Åpne denne publikasjonen i ny fane eller vindu >>Innovative noise control in ducts
2016 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The objective of this doctoral thesis is to study three different innovative noise control techniques in ducts namely: acoustic metamaterials, porous absorbers and microperforates. There has been a lot of research done on all these three topics in the context of duct acoustics. This research will assess the potential of the acoustic metamaterial technique and compare to the use of conventional methods using microperforated plates and/or porous materials. 

The objective of the metamaterials part is to develop a physical approach to model and synthesize bulk moduli and densities to feasibly control the wave propagation pattern, creating quiet zones in the targeted fluid domain. This is achieved using an array of locally resonant metallic patches. In addition to this, a novel thin slow sound material is also proposed in the acoustic metamaterial part of this thesis. This slow sound material is a quasi-labyrinthine structure flush mounted to a duct, comprising of coplanar quarter wavelength resonators that aims to slow the speed of sound at selective resonance frequencies. A good agreement between theoretical analysis and experimental measurements is demonstrated.

The second technique is based on acoustic porous foam and it is about modeling and characterization of a novel porous metallic foam absorber inside ducts. This material proved to be a similar or better sound absorber compared to the conventional porous absorbers, but with robust and less degradable properties. Material characterization of this porous absorber from a simple transfer matrix measurement is proposed.The last part of this research is focused on impedance of perforates with grazing flow on both sides. Modeling of the double sided grazing flow impedance is done using a modified version of an inverse semi-analytical technique. A minimization scheme is used to find the liner impedance value in the complex plane to match the calculated sound field to the measured one at the microphone positions.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2016. s. 69
Serie
TRITA-AVE, ISSN 1651-7660 ; 58
Emneord
Locally resonant materials, slow sound, acoustic impedance, metallic foam, low frequency noise, mufflers, lined ducts, grazing flow, flow duct, impedance eduction.
HSV kategori
Forskningsprogram
Farkostteknik
Identifikatorer
urn:nbn:se:kth:diva-192927 (URN)978-91-7729-119-0 (ISBN)
Disputas
2016-10-21, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Forskningsfinansiär
EU, FP7, Seventh Framework Programme, 289352
Merknad

QC 20160923

Tilgjengelig fra: 2016-09-23 Laget: 2016-09-23 Sist oppdatert: 2016-09-23bibliografisk kontrollert

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