Innovative noise control in ducts
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
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.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 69 p.
TRITA-AVE, ISSN 1651-7660 ; 58
Locally resonant materials, slow sound, acoustic impedance, metallic foam, low frequency noise, mufflers, lined ducts, grazing flow, flow duct, impedance eduction.
Research subject Vehicle and Maritime Engineering
IdentifiersURN: urn:nbn:se:kth:diva-192927ISBN: 978-91-7729-119-0OAI: oai:DiVA.org:kth-192927DiVA: diva2:973847
2016-10-21, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Ih, Jeong-Guon, Professor
Åbom, Mats, ProfessorBodén, Hans, ProfessorElnady, Tamer, Professor
FunderEU, FP7, Seventh Framework Programme, 289352
QC 201609232016-09-232016-09-232016-09-23Bibliographically approved
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