Sökning: "Sound absorption"

Visar resultat 1 - 5 av 29 avhandlingar innehållade orden Sound absorption.

1. 1. Absorption of Sound : On the effects of field interaction on absorber performance

   Författare :Anna Färm; Mats Åbom; Ragnar Glav; Susann Boij; Gareth Bennett; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sound absorption; Porous absorbers; Bulk reaction; Local reaction; Boundary layer; Grazing flow; Temperature gradients; Surface impedance; Sound field; Pass-by noise; Vehicle and Maritime Engineering; Farkostteknik;

   Sammanfattning : Environmental noise has for decades been a well known problem, especially in urban areas. As noise requirements for vehicles are sharpened, noise reducing concepts are needed in early design stages requiring accurate simulations to support the design. LÄS MER

3. 2. Analysis of Acoustic Absorption with Extended Liner Reaction and Grazing Flow

   Författare :Anna Färm; Mats Åbom; Lars Enghardt; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sound absorption; acoustic lining; non-locally reacting; boundary layer; grazing flow; sound field; transfer matrix method;

   Sammanfattning : 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. LÄS MER

4. 3. Glass mat reinforced thermoplastics - material, process and selected applications

   Författare :Jan Wahlberg; Industriell Produktion; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Material technology; recycling; sound absorption; energy absorption; vibrational energy; microtension; processing; Glass fibre; thermoplastics; Materiallära; materialteknik;

   Sammanfattning : The work presented in this thesis covers the processing of glass mat reinforced thermoplastics, GMT, and the mechanical properties of this material group. The thesis evaluates the possibilities of the material group from a processing and mechanical properties point of view. LÄS MER

5. 4. Micro-structural based acoustic modelling of anisotropic open cell materials

   Författare :Eva Lundberg; Huina Mao; Bradley Semeniuk; Peter Göransson; Mathieu Gaborit; Romain Rumpler; Peter Göransson; Elke Deckers; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; sound absorption; vehicle; anisotropic; foam; micro-structure; resource efficient; transfer matrix method; ljudabsorption; anisotrop; skum; mikrostruktur; TMM; fordon; resurseffektiv; Farkostteknik; Vehicle and Maritime Engineering;

   Sammanfattning : A method for the calculation of the acoustic performance of open-cell foammaterials is discussed. From a known micro-structural geometry and theconstituent material, the relevant acoustic properties are computed using apreviously published analytical method for the calculation of the dynamicdrag impedance and a previously published method for the calculation of theelastic moduli. LÄS MER

7. 5. Acoustic scattering in ducts and influence of flow coupling

   Författare :Susann Boij; KTH; []
   Nyckelord :sound; vortex sheet; flow separation; end correction; Strouhal number; non-orthogonal modes; energy balance; TECHNOLOGY; TEKNIKVETENSKAP;

   Sammanfattning : The subject of this thesis is the acoustic properties offlow duct area expansions and the influence of flow-acousticcoupling at sharp edges. For low Mach number flow, significantinteraction between the sound field and the flow field canoccur at such points of flow separation. LÄS MER