Multimodal experimental and numerical characterization of acoustic performance in built environments via hybrid acoustic metrology

The research described in the article addresses the problem of measurement, prediction and practical use of the acoustic properties of materials determined in an impedance tube. The aim of the research was to develop a simple calculation model for the insertion loss of small machinery enclosures, based on the normal incidence sound transmission loss and the normal incidence sound absorption coefficient of porous and fibrous materials. Both experimental and model tests were carried out on materials such as mineral wool, melamine foam and rebonded polyurethane foam. Assessing the absorption properties of the tested porous and fibrous materials was performed using selected theoretical models, relating the calculations of the normal incidence sound absorption coefficient to measurements of this parameter conducted using an impedance tube. The application of the modified Allard and Champoux model brought the best results with the smallest discrepancies of the obtained results in relation to the experimental tests. Assessing the sound-insulating properties of the tested mineral wool was carried out using the proposed calculation model for the normal incidence sound transmission loss, relating the obtained results to measurements conducted using an impedance tube. The assessment of the sound-insulating properties of porous and fibrous materials was performed using the proposed calculation model for insertion loss, which was validated using two prototype test stands for determining the insertion loss of cubic enclosures, in this case with walls made of porous and fibrous materials. Satisfactory results were obtained for engineering applications in the calculation results using the proposed models with respect to measurements. The results may have practical applications in assessing the effectiveness of acoustic enclosures, in which the basic construction material is an appropriate porous or fibrous plate, selected to have both sound-absorbing and sound-insulating properties.

ABSTRACTThe paper presents the results of research concerning three fiber materials – hemp fiber, cellulose fiber and mineral wool as a loose-fill thermal insulation materials. It focused on the study of moisture properties and wettability of these materials. The analysis involved evaluation of moisture sorption in different relative humidity conditions and evaluation of wettability of fibers by contact angle measurement. The study showed that the sorption equilibrium has been achieved at different times, which proves the various nature and properties of the materials. Hemp fibers were less wet than cellulose fiber, but the time needed to stabilize was shorter. The largest contact angles, indicating the strongly hydrophobic properties, were shown by mineral wool. Some samples of hemp and cellulose fibers were characterized by similar contact angles providing high wetting properties.

Architected materials are a new class of engineered materials with carefully controlled internal structures that give rise to properties that differ from or surpass those of their constituent materials. Recent advances in additive manufacturing provide an extraordinary opportunity to rationally design the structure and the chemical composition of architected materials across multiple length scales to optimize properties and functionalities for a variety of applications. These functional architected materials are capable of decoupling critical trade-offs, such as strength vs. density, to reach new regions of the material property space, and enabling exotic properties that rarely exist in classical materials such as negative refraction and negative thermal expansion. This thesis probes into the dynamic behaviors of architected materials undergoing electrochemical reactions and aims to provide an in-depth understanding of the underlying mechanisms as well as design principles generalizable for other functional architected material systems. We developed novel fabrication methods based on two-photon lithography and various physical and chemical post-processing techniques to create architected materials with multi-level design freedom including feature sizes, structural geometries, and material compositions, which resonates with the multi-faceted challenges in electrochemical systems. We demonstrated that architected materials provide a new platform to design battery electrodes that could accommodate the large volumetric changes associated with conversion-based electrode materials, while decoupling the longstanding trade-off between active material loading and transport kinetics in batteries. Furthermore, we presented a new class of electrochemically reconfigurable architected materials that could transform their structures in a programmable, reversible and non-volatile fashion, which provide new vistas for designing mechanical metamaterials with tunable phononic bandgaps and deployable micro-devices for biomedical applications. The multi-scale and multi-physics nature of these electrochemically driven architected materials prompted us to develop a toolset of (1) in situ SEM and optical microscopy to visualize the dynamic responses, (2) coupled chemo-mechanical finite element analysis to reconstruct detailed mechanical evolution as electrochemical reactions proceed, and (3) a statistical mechanics framework to capture the transient interactions between coupled mechanical instabilities. Using these tools, we investigated lithiation-induced cooperative beam buckling in tetragonal Si microlattices: from the deformation mechanisms of individual beams and the cooperative coupling between buckling directions of neighboring beams to the lithiation rate-dependent distribution of ordered buckling domains separated by distorted domain boundaries. Results indicate that local defects and stochastic energy fluctuations play a critical role in the dynamic response of architected materials in a way analogous to that during phase transformations of classical materials. These connections have profound implications on how we could understand and design architected materials by drawing inspiration from established theories in materials science.

The construction and demolition (C&D) industry has been identified as a major source of waste. European Union legislation states that, by 2020, 70 % of C&D waste must be prepared for reuse, recycled or recovered. European Union member states must increase their C&D waste recycling percentages in order to meet this binding target. Utilization of mineral wool waste, often considered unrecyclable, could improve the recycling percentage of C&D waste. In this article, mineral wool production and waste volumes are estimated based on information from the Eurostat database. A literature survey is conducted to collect information about mineral wool material properties, current recycling methods, and barriers to recycling of mineral wool, and suitable methods for separating mineral wool from C&D waste streams and the economic viability of mineral wool recycling are discussed. It is noted that accurate estimation of mineral wool waste volumes is problematic due to the fragmented nature of available data. Based on the literature review, current methods for recycling mineral wool waste include utilization of mineral wool waste as a raw material in various products. Barriers to recycling include economic questions and issues related to the purity and health effects of mineral wool waste. Material properties of mineral wool waste, such as fire resistance, could provide improved properties in products utilizing mineral wool waste as a raw material.

Experimental assessment of the water content influence on thermo-acoustic performance of building insulation materials

Sound absorbers play a significant role in keeping a quiet and noise-free environment. Both synthetic and natural materials can use to control noise. Currently, natural materials are a valid alternative to conventional synthetic materials. This paper aims to study the physical parameters of Grewia Optiva fibers. The theoretical models’ assessment has been carried out to calculate the sound absorption coefficient with the help of Scilab software for synthetic (melamine foam, polyurethane foam, and mineral wool) and natural (kenaf fiber, coir fiber, and Grewia Optiva fiber) materials. The results from the simulation conclude that the sound absorption coefficient of Grewia Optiva fiber is almost similar to or much better than other synthetic and natural sound absorbers. Hence, Grewia Optiva fibers can be a valid substitute for traditional sound absorbers for sound absorption purposes.

Modern houses and apartments are built with flat roof and often the upper apartments contain a roof terrace. Impact noise has been measured from a roof terrace with floating floor on mineral wool, a good wooden construction with 2 layers of gypsum stiff fastened in the ceiling. This measurement shows L'n,w of 55 dB, and make it necessary with better solution for ceiling to achieve L'n,w 53 dB or better. Two measurements for improved situation in different buildings are done with ceiling in Sylomer hangers and with free ceiling. These two situations show L'n,w of 50 and 46 dB. The measurement of solution with free ceiling shows the lowest value of L'n,w for these two elastic solutions and also has the lowest levels in the low frequency range. This paper will show that for roof terrace the need for elastic or free ceiling is important. Concerning annoyance and low frequency noise, solution with free ceiling is to be preferred in future projects. There has been no complaining about impact noise from roof terrace, for the situation with free ceiling. For the situation with Sylomer hangers people living there hear some noise, but they have not complained about that.

The air flow resistance is a fundamental acoustic parameter to understanding the properties of cellulose based insulation material, it is useful for research and development to perform acoustic performance prediction and for calculation modelling. There is a connection between structure of cellulose based insulation material and its acoustic characteristics. Specific air flow resistance is also a parameter for the quality of cellulose based insulation which is used for factory production control because there is also strong connection between specific air flow resistance and density of produced material. Experimental measurement of airflow resistance has been performed according to the direct method of the EN 29053 standard where low and constant air flow is passed through cellulose based insulation with a specific section.

Floating floors are widely used to reduce the floor impact noise in ship cabins as well as in multi-dwelling buildings. The most common material for impact absorption in floating floor structure is mineral wool, where high density and sufficient thickness is also needed for fire-resistant requirement in ships. For proper design of floating floors, it is essential to understand how the performance of floating floor is affected by the design parameters such as changes of the mineral wool thickness, density, fiber direction and the use of viscoelastic layer. In this paper, noise reduction performance of the floating floor for use in cruise ship cabin is studied. A mock-up is built by using 6 mm steel plate, and two identical cabins are made of 25 mm sandwich panel inside the steel structure. Various floating floor systems are tested by employing the mock-up. The measurements show that viscoelastic layer is effective when it is used to form a constrained layer. However, viscoelastic layer becomes insignificant when mineral wool is present. It is found that impact noise becomes quieter by 7 dB when fiber direction of the mineral wool is changed from vertical to horizontal, and increasing density of mineral wool from 140 kg/m 3 to 240 kg/m 3 results in an increase of 9 dB. It is also observed that floor SBN (Structure-Borne Noise) is greater than side wall SBN by 10-15 dB up to 2000 Hz, which means that side wall SBN can be neglected in evaluating floor impact noise of ship cabin at frequencies up to 2000 Hz.

Fabrication of multifunctional cu-coated melamine foam by electroless chemical deposition technique for thermal management, EMI shielding, and antibacterial applications

The present paper examines the impact noise transmission through some floor building assemblies using different approaches. Firstly, the Acoubat software has been used to simulate the impact noise transmission through different floor configurations used in Algerian construction mode. The results are compared with the available measurements based on Bruel and Kjaer 2260 sound level meter analyzer equipment. The results of the first method show that the different cases of floor configurations need some improvement to ensure the acoustic comfort in the receiving apartment. The addition of resilient underneath tile reduces the impact noise level from 67 dB to 57 dB. When the polyethylene and mineral wool are used, the results showed that the total level of the impact noise can be achieved \( {\text{L}}_{{{\text{nT}},{\text{w}}}}^{\prime } \) = 56 dB and \( {\text{L}}_{{{\text{nT}},{\text{w}}}}^{\prime } \) = 54 dB, respectively. In conclusion, the recommended value of the impact sound level in the receiving room should not exceed 58 db. Secondly, we have developed two experimental methods, (i) field method in multi-storey residential building, and (ii) laboratory method using the following equipment: sound level meter analyzer Bruel and Kjaer 2270 with accelerometer Bruel and Kjaer 5408, BZ 5503 software, and impact-tapping machine Bruel and Kjaer 3204. The laboratory method is good way to estimate the weighted sound reduction index of resilient materials mixed with mortar or layer placed under tile. The results show that the weighted sound reduction index of resilient layer can reach 18 dB, 6.6 dB and 11.6 dB for the rubber, PVC and Bitumen layer, respectively. The important results obtained in this paper can be used as platform to improve the acoustic rehabilitation of the multi-storey residential building.

건축 재료는 건축을 구상하는 중요한 부분 중 하나다. 그러나, 재료를 사용해도 건물의 아름다움을 다루어지는 것이 늘 쉽지 않고 도전적이다. 하지만, 요즘 건축 프로젝트에 대한 관찰을 통해 건축 재료의 사용에 관련적인 공통성이 있다는 것을 밝혔다. 따라서, 본 연구는 신경미학과 진화미학의 선행연구와 건축 재료를 탐구하기로 했으며, 새로운 관점과 개념으로 재료의 시각적 특성 및 이에 대한 선호를 집중하여 논의하였다. 건축 표피 재료가 가진 의미와 미적 가치의 정의로 시작하였는데 이에 대한 기존 연구를 통해 아직 검토하기 어려운 점을 발견했다. 그래서 과학적인 관점으로 인간의 뇌 시각 자극 처리 과정을 살펴본 후, 미적 인식의 생성을 논의하기 위해 신경 미학 연구를 도입했다. 복측과 배측경로에 관한 조사는 인간이 어떻게 미적 인식을 생성했는지에 대한 과정이 명확히 했으며, 인간은 시각적 자극을 통해 아름다움에 대한 식별이 될 수 있는 사실을 알게 되었다. 또는 미의 공통성과 어떤 시각 요소를 인간의 미의식을 불러일으킬 수 있는 것을 살펴보기 위해 진화미학적인 선행연구를 도입하여 이 근거로 인류의 선천적인 미학적 감각이 생존본능과 연관이 있다는 사실을 밝혔다. 이어, 시각적 특성에 대한 인간의 인식 결과와 재료의 시각적 특성에 대한 선호를 확보하기 위해 2 단계의 설문이 수행되었다. 결과에 따라, 인간이 특정한 시각적 요소에 대한 높은 호감성을 가지고 있다는 것을 명확히 할 수 있었다. 그 이유는 앞서 언급했던 신경미학과 진화미학과의 근본적인 연관성을 가질 수 있었기 때문에 미적 교육을 받지 않은 사람들도 기본적인 능력으로 아름다움을 감상할 수 있다고 확인하였다.Material is one of the critical parts to construct architecture. However, using materials to shape the aesthetics of the architecture has always been a challenging part for designers. Somehow, through recent projects it seems that there are some common relevance in the use of architectural materials. Therefore, of this research used neuroaesthetics and evolutionary theories to investigate architectural materials, started from defining the meaning of architectural exterior materials and their aesthetic value, discovered the shortcomings of current research on building materials, then analyzed the human brain s perception process of visual stimuli from the scientific perspective to confirm what visual characteristics can be perceived immediately. Next, introduced neuroaesthetics studies to discuss the generation of beauty cognition. The survey on the ventral and dorsal pathways clarified the process of how humans generated aesthetic cognition and human indeed be conscious of the perception of beauty through visual stimuli. To dig into the commonality of beauty and what visual component could arouse humans beauty consciousness, used the advanced research of evolutionary aesthetics. To confirm the results of humans perception of visual characteristics and their preference of visual properties of materials, two stages of investigation has been conducted. Through the results, it can be clarified that humans have a higher degree of favorability towards specific visual elements. Exploring the reasons can have a grounded association with neuroaesthetics and evolutionary aesthetics. At the same time, it is confirm that even those who have not received aesthetic education have a certain degree of ability to appreciate beauty.

In this paper, we present a workflow developed for designing with and scaling-up new materials in architecture through an iterative cycle of materialization and testing. The framework establishes a connection between design requirements and form, taking advantage of different scales in new materials known as micro, meso, and macroscale in the process of design/manufacture. Different scales when dealing with material systems-especially in those that possess some level of uncertainty in their behavior from the formation process-make it challenging to deal with the different material variables controlled at each scale. This paper presents a brief review of existing design workflows centered on material properties. We then discuss case studies and argue for a multi-scale approach for design. Finally, we present the workflow. By implementing the workflow on two case studies, we answer how we can include material scales and their embedded properties as the central part of the design/manufacture process to aid in implementing new materials in architecture. The case studies are a responsive skin system and a free-standing tensile structure incorporating 3D printed wood filament and knitted yarn as the primary material.

Superelastic cellular NiTi tube-based materials: Fabrication, experiments and modeling

In this study, new empirical models for predicting the airflow resistivity, sound absorption coefficient of polyfelt fibrous materials have been developed. The empirical models were presented as simple power-relations by least square best fitting method of impedance tube and flow bench test data over a set of 14 samples. Two coefficients were identified for a new empirical formula to predict the airflow resistivity from the mass density and thickness of polyfelt materials and eight coefficients were identified for a new empirical formula to predict the characteristic acoustic impedance, propagation coefficients and sound absorption coefficient from the airflow resistivity. For the given mass density and thickness of a polyfelt fibrous material, the outcome proposed in this paper enables a quick and accurate evaluation of the acoustic properties of the material such as the airflow resistivity and sound absorption coefficient without a further requirement of flow bench and impedance tube tests. This is because that the predicted results from the new empirical models are closer to the measured results in the frequency range of interest than the other models in the previous work in the published literatures.