Sökning: "ljudabsorption"

Hittade 4 avhandlingar innehållade ordet ljudabsorption.

1. 1. 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

3. 2. Modeling of sound-turbulence interaction in low-Mach-number duct flows

   Författare :Chenyang Weng; Mats Åbom; Susann Boij; Avraham Hirschberg; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Järnvägsgruppen - Ljud och vibrationer; Järnvägsgruppen - Ljud och vibrationer;

   Sammanfattning : When sound waves propagate in a duct in the presence of turbulent flow, tur- bulent mixing can cause extra attenuation of the sound waves in addition to that caused by the viscothermal eects. Experiments show that compared to the vis- cothermal eects, turbulent absorption becomes the dominant contribution to the sound attenuation at suciently low frequencies. LÄS MER

4. 3. Absorption Characteristics of Periodically Perforated Suspended Ceilings

   Författare :Dag Holmberg; Teknisk akustik; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Building construction; Byggnadsteknik; measurement device.; flow resistance; suspended ceilings; periodically perforated facing; resonant absorbers; Room acoustics; building acoustics;

   Sammanfattning : The sound absorption characteristics of resonant absorbers, implemented as perforated suspended inner ceilings attached with thin porous layers, are investigated. Several existing theories model the principal absorption mechanisms, but the interaction with the outer sound field influences the absorption in ways that can be modelled with new approaches. LÄS MER

5. 4. Foam, Fire and Free Volume - Chemical and Physical Aspects of Porous Polymers

   Författare :Anna Andersson; Centrum för analys och syntes; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Poisson ratio; vibration damping; acoustic impedance; cell morphology; hyperbranched polymer; Polymer foams; free volume; positron annihilation; supercritical fluid.;

   Sammanfattning : Automotive seating has been under continous development since it was described for the first time in 1885. At that time one could read about a “padded leather bench seat sitting on springs mounted directly to the frame of a horse-less carriage”. LÄS MER