Sound Absorption in Porous Materials.

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Hänninen, Tuomas Cucharero Moya, Jose 2017-12-18T12:16:20Z 2017-12-18T12:16:20Z 2017-12-11
dc.description.abstract Porous materials have been the most commonly used materials to dissipate sound energy and reduce sound reflections. The popularity of these materials resides in their ability to efficiently absorb sound at mid and high frequencies using relatively thin layers. Dissipation of sound energy in porous materials occurs through the interconnected pores due to viscous, thermal and inertial effects caused by the interaction between the fluid and the solid phases. Measurements of the sound absorption coefficients of sound absorbing materials are generally performed using the reverberation chamber or the impedance tube methods. The two of them are laboratory measurement techniques. The impedance tube methods compute the absorption coefficients only considering normal incident sound waves, whereas the reverberation chamber method assumes diffuse field, that is, sound arriving the absorbing material from all directions. The ability of porous materials to absorb sound strongly depends on their physical characteristics. These include porosity, tortuosity, shape of the pores, and flow resistivity. The physical properties of the total system determine the final sound absorption coefficients. The physical properties of the system include thickness and bulk density of the porous layer, and size of the particles forming the material. Theoretical, semi-phenomenological, and empirical models have been developed to predict the sound absorption properties of porous materials. It has been demonstrated that the most popular models, which were developed to predict the sound absorption properties of mineral wool porous materials, do not accurately predict the sound absorption coefficient of porous materials made of natural cellulose fibres. New parameters have to be added to the models. en
dc.format.extent 78+13
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.title Sound Absorption in Porous Materials. en
dc.type G2 Pro gradu, diplomityö fi Sähkötekniikan korkeakoulu fi
dc.subject.keyword porous en
dc.subject.keyword absorption en
dc.subject.keyword sound en
dc.subject.keyword modelling en
dc.subject.keyword cellulose en
dc.subject.keyword impedance en
dc.identifier.urn URN:NBN:fi:aalto-201712188171
dc.programme.major Signal, Speech and Language Processing en
dc.programme.mcode ELEC3030 fi
dc.type.ontasot Master's thesis en
dc.type.ontasot Diplomityö fi
dc.contributor.supervisor Lokki, Tapio
dc.programme CCIS - Master’s Programme in Computer, Communication and Information Sciences (TS2013) en
dc.ethesisid Aalto 9704
dc.location P1 fi

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