Browsing by Author "Cucharero Moya, Jose"

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  • Akustiikkamateriaalien kulmariippuvainen äänenabsorptio
    (2021-11-24) Cucharero Moya, Jose; Hänninen, Tuomas; Lokki, Tapio
     A4 Artikkeli konferenssijulkaisussa
    Esittelemme tässä artikkelissa vaihtoehtoisen tavan mitata äänen absorptio-ominaisuuksia 2D-goniometrillä. Laitteistolla voidaan mitata materiaalin äänen absorptiokerroin äänen eri tulo- ja heijastuskulmilla. Menetelmä perustuu ensimmäisten heijastusten erotteluun muista häiritsevistä heijastuksista aikaikkunoinnilla. Menetelmän etuna on helppo näytteen valmistus, suhteellisen pieni näytekoko ja mahdollisuus mitata helposti perforoituja näytteitä. Menetelmällä saadut tulokset korreloivat hyvin jälkikaiuntahuone- ja impedanssiputkimittauksista saatuihin tuloksiin ja auttavat ymmärtämään materiaalien äänen absorptiota entistä laajemmin.
  • Angle-Dependent Absorption of Sound on Porous Materials
    (2020-10-16) Cucharero Moya, Jose; Hänninen, Tuomas; Lokki, Tapio
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Sound-absorbing materials are usually measured in a reverberation chamber (diffuse field condition) or in an impedance tube (normal sound incidence). In this paper, we show how angle-dependent absorption coefficients could be measured in a factory-type setting. The results confirm that the materials have different attenuation behavior to sound waves coming from different directions. Furthermore, the results are in good agreement with sound absorption coefficients measured for comparison in a reverberation room and in an impedance tube. In addition, we introduce a biofiber-based material that has similar sound absorption characteristics to glass-wool. The angle-dependent absorption coefficients are important information in material development and in room acoustics modeling.
  • Influence of moisture on the sound absorption properties of wood-based pulp fibre foams
    (2024-09) Cucharero Moya, Jose; Awais, Muhammad; Valkonen, Mikko; Kammiovirta, Kari; Rautkari, Lauri; Lokki, Tapio; Hänninen, Tuomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The use of wood fibres, and other biofibres in general, as raw materials to produce sound absorbers has gradually increased lately. The main reason for their increased use is their contribution to reducing CO2 from the atmosphere by binding CO2 into the building structure for decades. Understanding of the ultrastructure of wood fibres is essential as it has a strong influence on the fibre properties, and thus, on the final material properties. In this work, the effect of moisture on the sound absorption properties of wood-based pulp fibre foams has been studied. It is shown that increasing moisture content (> 9%) in pulp fibres leads to greater sound absorption at low-mid frequencies. Fibre swelling, increasing fibre flexibility, and increasing foam bulk density with increasing fibre moisture content are hypothesized as the causes for the increase in sound absorption. Hygroexpansion, mechanical properties as well as moisture absorption capability of different types of pulp fibres are studied and related to their sound absorption properties. It is concluded that, in addition to fibre diameter and bulk density of foams, the elastic properties of the pulp fibres are partially responsible for the improved sound absorption of the foams exposed to greater relative humidity conditions.
  • Influence of Sound-Absorbing Material Placement on Room Acoustical Parameters
    (2019-08-07) Cucharero Moya, Jose; Hänninen, Tuomas; Lokki, Tapio
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The reverberation of a room is often controlled by installing sound absorption panels to the ceiling and on the walls. The reduced reverberation is particularly important in classrooms to maximize the speech intelligibility and in open-plan offices to make spaces more pleasant. In this study, the impact of the placement of the absorption material in a room was measured in a reverberation room and in a mockup classroom. The results show that absorption material is less efficient if it is mounted to the corners or on the edges between the walls and ceiling, if the sound field is more or less diffuse. If the room modes dominate the sound field, the most efficient location for the sound-absorbing material was found at one of the surfaces causing the modes. The results help acoustical consultants to place the absorption material in optimal locations and, generally, minimize the amount of material and save costs.
  • Preparation of Fully Bio-based Sound Absorbers from Waste Wood and Pulp Fibers by Foam Forming
    (2023-02-08) Valkonen, Mikko; Cucharero Moya, Jose; Lokki, Tapio; Rautkari, Lauri; Hänninen, Tuomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Building materials that are bio-based and produced from waste streams have a substantial effect on the carbon footprint of buildings. In this study, the authors prepared fully bio-based sound absorbers from waste wood and other cellulosic materials. Cutter shavings (CSs), softwood pulp, and cellulose powder (CP) were used as raw materials to prepare sound absorber samples using the foam-forming technique. The fully bio-based sound absorbers prepared were mechanically stable. However, an increase in CSs content decreased their mechanical properties, and samples with high CSs content became difficult to handle. The CP increased the mechanical properties, but it did not affect the sound absorption of the samples. The sound absorption properties of these fully bio-based materials could be tuned by carefully selecting CSs and fiber contents and adjusting the thickness of the material. Greater CSs content decreased the sound absorption properties of the materials. This decrease was mainly due to an increase in the average pore size, leading to poorer sound energy dissipation by visco-thermal effects.
  • Sound Absorption in Porous Materials.
    (2017-12-11) Cucharero Moya, Jose
     Sähkötekniikan korkeakoulu | Master's thesis
    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.
  • Sound absorption properties of wood-based pulp fibre foams
    (2021-05) Cucharero Moya, Jose; Ceccherini, Sara; Maloney, Thaddeus; Lokki, Tapio; Hänninen, Tuomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this study, sound absorbing materials were produced through foam forming technique using hardwood and softwood pulps with varying chemical composition, ultrastructural, and morphological properties as raw materials. The sound absorption properties of the produced foams were measured and related to the ultrastructure and the morphology of the pulp fibres. All the fibre foams provided sound absorption properties comparable to those of conventional porous materials used for acoustic purposes. In general, further processing, as well as smaller fibre dimensions contribute to improve the sound absorption properties of the pulp fibre foams. The results provide valuable insight on the optimization of wood-based sound absorbing materials.
  • Studies on the sound absorption properties of wood-based pulp fibre foams
    (2022-10-25) Cucharero Moya, Jose; Ceccherini, Sara; Awais, Muhammad; Kammiovirta, Kari; Maloney, Thaddeus; Rautkari, Lauri; Lokki, Tapio; Hänninen, Tuomas
     A4 Artikkeli konferenssijulkaisussa
    Acoustic behaviour of wood fibres depends on material properties on different hierarchical structural levels, including molecular, microscopic, and macroscopic. In this paper, we present comprehensive studies on the effect of the hierarchical structure of wood pulp fibres on acoustical properties. In the molecular level, structural polymers of wood and their arrangement in the cell wall are crucial in determining the material properties of the fibres. In the microscopic level, wood fibres are characterised by an irregular morphology and present average fibre lengths and widths ranging from 0.4 – 6 mm and 10 – 50 µm, respectively. In the macroscopic level, the porous structure of a 3D-fibre network formed by means of foam-forming technique depends on the raw fibres as well as on the foam forming procedure used. The studied pulp fibre foams achieve comparable sound absorption properties to those of conventional synthetic porous materials. Increasing use of wood based materials in buildings contribute to reduce CO2 from the atmosphere by binding CO2 into the building structure for decades.
  • Vaimennusmateriaalin sijoituksen vaikutus huoneakustiikkaan
    (2019-10-28) Cucharero Moya, Jose; Hänninen, Tuomas; Lokki, Tapio
     A4 Artikkeli konferenssijulkaisussa