A Numerical Investigation of the Trade-Off Between Sound Insulation and Air Ventilation for a Partially Open Door

Helmholtz resonator(HR) has already been demonstrated both theoretically and experimentally to be a metamaterial with negative mass density and negative bulk modulus simultaneously. The HR can resonate at a frequency corresponding to a wavelength much longer than its geometrical parameters. At this time, the incident acoustic energy can be located. Therefore, the HR structures are considered to be good choices for controlling low-frequency sound waves. Furthermore, existing results indicate that the wide forbidden band could be formed by a one-dimensional structure shunted with detuned HRs. Based on these aforementioned theories, a man-made acoustical structure with broadband low-frequency sound insulation effect is designed by circularly inbuilt HRs. Beyond this structure's surface, a two-dimensional quiet zone can be created. With the same simulated model, an experimental structure is fabricated based on PVC plastic material. The structure consists of five layerd circular plates. In the top four plates, two kinds of holes are drilled. The smaller holes in the top plate act as shot necks of the HR, while the bigger holes in the middle three plates serve as the cavities of the HR. They can construct 60 resonators with different resonant frequencies. Experiments are carried out to study its sound insulation properties. In the experiments, three kinds of HRs with resonant frequencies 785, 840 and 890 Hz from inner loop to outer loop, respectively, are formed. The experimental results are very coincident with the simulation results from the software of COMSOL Multiphysics based on finite element method, which shows that this structure has an excellent sound insulation effect in a frequency band of 680-1050 Hz, and the maximum insulation sound pressure level can reach 41 dB. Meanwhile, the distribution of the two-dimensional sound field is measured. The results point out that the range of the insulation area can be changed with the incident frequency. In addition, the sound insulation effect is sensitive to the resonant state of the HRs. When all of the resonators at the same loop resonate simultaneously, the insulation sound pressure level will be higher. On the contrary, the insulation sound pressure level will be lower because of the energy leaking through the positions where the HRs do not resonate with the others. This work will be of help for designing new sound protection devices for low-frequency sound waves.

In this paper, a three-component cladding acoustic metamaterial panel with good sound insulation effect in the low-frequency range is proposed. The sound transmission loss of metamaterial panels under different structural configurations and different material parameters is investigated by combining finite element simulation calculations with experimental research. The results show that the closer the center of gravity of the scatterer is to the substrate, the better the stability of the resonance unit, the wider the range of effective sound isolation frequencies, and the higher the degree of normalization. The filling rate of the scatterer is maintained at about 0.5 to obtain a better sound insulation effect. At the same time, choosing lower density materials for the substrate and metal materials with high density and high modulus of elasticity for the scatterer can maximally widen the bandgap and allows for low-frequency sound insulation below 600 Hz. This approach improves the low-frequency sound insulation efficiency of acoustic metamaterials. The results provide important explanations and references for a deeper understanding of the sound insulation mechanism and the effects of different parameters on sound insulation.

To meet objectives such as the sound insulation characteristics of timber structures and the comfort of residents, this study assessed an ordinary floor and three kinds of floating floors (Portuguese cork, graphite polystyrene sound insulation boards and expanded polypropylene plastic foam boards) in the same bedroom of a two-storey light wooden building. Adopting standard white noise and music noise excitation, structural design, theoretical checks and sound insulation tests of the floors were conducted. For the four floor structures, the sound insulation volume, sound pressure distribution characteristic spectrum of the building floor under different noise source environments, the frequency characteristics of the noise source, the multiple relationship of the sound insulation sound pressure level and the sound insulation mechanism were analysed. It was found that the sound pressure multiple of the space separating the upper and lower floors of the building was 8–18 times greater than that of the light wooden floor structure. The airborne sound insulation volume–frequency curves of the four floors, calculated by the transfer matrix method, were consistent with the actual measured values. The sound insulation effect was better in the low and middle frequencies.

The new composite concrete with both lightweight, thermal insulation, heat insulation and light transmission properties is a new type of building The new composite concrete with both lightweight, thermal insulation, heat insulation and light transmission properties is a new type of building material with energy saving and consumption reduction functions. This paper integrates the research status of scholars in this field at home and abroad, realises the lightweight of blocks by studying the properties of lightweight aggregate concrete and porous concrete, and selects suitable light- transmitting materials, tests the light transmittance and mechanical properties of concrete blocks after adding light-transmitting materials, then analyzes the advantages and disadvantages of the sound insulation effect produced by adding soundproofing materials made from different materials to concrete blocks, and selects the best sound insulation effect by adding soundproofing materials to concrete blocks. concrete blocks, and selects the best soundproofing material for the comprehensive performance. Then we analyze the advantages and disadvantages of Then we analyze the advantages and disadvantages of adding different sound insulation materials into concrete blocks, and select the best sound insulation material with comprehensive performance. the same time of realising the three properties of light weight, sound insulation and light transmittance, we further study the effect of adding different thermal insulation materials on the thermal insulation effect of the blocks, and select the concrete blocks with the best thermal insulation performance.

To meet users’ needs for the building comfort, this article researched the impact sound insulation performance of timber floor structure under different conditions. The research has been done on a common floor covering and three floating floor coverings (composed of Portuguese cork board, a kind of improved graphite polystyrene sound insulation board (BGL) and expanded polypropylene sound insulation board (EPP) respectively) in the same bedroom in a two-story light-weight timber structure. The tapping machine excitation and daily behavior excitation test methods have been used, and the field tests on the impact sound insulation of the floors under conditions that doors and windows are closed and doors and windows are opened have been validated. Based on the test result, the sound insulation effects has been analyzed; law of the sound pressure distribution of the noise sources and the change of sound pressure with frequency has been validated; the frequency characteristics of the noise sources has been summarized; and the optimization measures of sound insulation has been proposed. The main conclusions show that: the impact sound insulation effect of the floating floor is more significant than that of the ordinary floor, BGL floor has the highest impact sound pressure level improvement; the insulated sound pressure of the floating floors is 10–20 times more than that of the ordinary floor in condition of tapping machine; With the increase of the frequency, the measured impact pressure level of the floor decreases continuously, and the decrement of the impact sound of the floor increases; in the frequency range of 80-8000 Hz, the sound pressure distribution of the floating floor is lower than that of the ordinary floorsound pressure. The impact sound insulation test is expected to provide a useful reference for improving the sound insulation performance of the timber floor structure, and has high engineering application value for improving living comfort.

This article studies the application of biomimetic triangular non-smooth surface materials in automotive acoustic packaging and their effects on sound absorption and insulation performance. Firstly, the application of Statistical Energy Analysis (SEA) in predicting high-frequency vibration noise in automobiles was discussed. Due to the limitations of the acoustic finite element method in predicting high-frequency noise, the SEA method has gradually been widely applied and continuously improved in domestic and foreign research. This article establishes SEA models for the front panel and floor. It analyzes the performance of different acoustic packaging materials through simulation, focusing on the sound absorption and insulation effects of biomimetic non-smooth surface materials. The experimental results show that the acoustic packaging material with a three-layer structure has excellent sound absorption and insulation performance in the high-frequency range. Specifically, the acoustic packaging of the cowl panel and floor adopts a three-layer material structure composed of organic fiber, molded felt, polyurethane foam and sound insulation felt. The simulation results show that the PU foam material with a bionic triangular wedge surface has a sound absorption coefficient of 0.983 at 1,000 Hz, significantly better than the traditional smooth surface material. In addition, the sound insulation performance of the front panel and floor increased by 2.9 dB and 48.1 dB, respectively, at 5,000 Hz.

Power transformer is the main noise source of substation. In order to reduce the noise of transformer, this paper presents a double layer sound insulation wall structure of transformer tank. The sound insulation performance test of the sample based on the double wall panel structure is completed. Through the measured data and numerical simulation, the results show that the double-layer sound insulation panel has better sound insulation effect. When the air inside the sandwich space is pumped, the sound insulation volume is not significantly improved due to the deformation factor. The feasibility of this method is verified by experiments, which provides technical reference and experimental basis for noise control of oil-immersed transformer.

To solve the problem of low-frequency noise control in ship cabins, a new membrane-type acoustic metamaterial (MAM) with bulges on the surface of thin films is designed based on the characteristics of lightweight and low-frequency sound insulation of membrane-type acoustic metamaterials. The sound structure coupling module of COMSOL multiphysical field coupling software is used to analyse the sound insulation performance of MAMs. The sound insulation properties of the additional mass film and self-similar fractal convex structure are further discussed. The metamaterial structure studied in this paper has a better sound insulation effect than ordinary film, which provides strong technical support for ship cabin noise control.

Study on sound insulation performance of the periodic arrangement expansion chambers structure with built-in micro-perforated panel

In order to overcome the influence of the structural resonance on the continuous structures and obtain a lightweight thin-layer structure which can effectively isolate the low-frequency noises, an elastic membrane structure was proposed. In the low-frequency range below 500 Hz, the sound transmission loss (STL) of this membrane type structure is greatly higher than that of the current sound insulation material EVA (ethylene-vinyl acetate copo) of vehicle, so it is possible to replace the EVA by the membrane-type metamaterial structure in practice engineering. Based on the band structure, modal shapes, as well as the sound transmission simulation, the sound insulation mechanism of the designed membrane-type acoustic metamaterials was analyzed from a new perspective, which had been validated experimentally. It is suggested that in the frequency range above 200 Hz for this membrane-mass type structure, the sound insulation effect was principally not due to the low-level locally resonant mode of the mass block, but the continuous vertical resonant modes of the localized membrane. So based on such a physical property, a resonant modal group theory is initially proposed in this paper. In addition, the sound insulation mechanism of the membrane-type structure and thin plate structure were combined by the membrane/plate resonant theory.

Divers, who engage in search and/or rescue in a sunken or capsized ship, usually have no communication apparatus because of the complexity of the hull construction. For such divers, the most simple and effective way to provide some information is to transmit an acoustic signal directly by an underwater loudspeaker. Though the outer wall of the ship functions as a sound insulation wall, there is no appropriate evaluation method for the insulation effect of a wall to random sound pressure wave such as voice signal or noise.In this paper, a statistical evaluation problem concerning sound insulation effect of a wall in underwater is considered based on the idea of statistics such as Lα noise level, defined as the (100-α) percentile point of the noise level probability distribution. Concretely, a single wall is employed as the most basic model of the hull and a new statistical treatment is first proposed for the transmitted sound pressure wave in the case where a Gaussian type random sound pressure wave with an arbitrary power spectral density is passed through the wall, and next, an explicit expression for the sound insulation effect, defined as the difference between the Lα of the incident sound intensity and that of transmitted sound intensity, is derived as a function of the system parameters.Finally, the validity of the theoretical evaluation method is confirmed by an analog simulation and a water tank experiment using several kinds of single walls.

In this study, a test device was designed and established for evaluating the sound insulation of fabrics, and six warp knitted fabrics with different parameters were chosen and tested. The results show that these fabrics have different sound insulation effect to various sound wave frequencies, and normally, the fabric with solid structure has better sound insulation effect that the fabric with thin structure, but the effect of latter fabric can be improved by using some treatments.

In today’s highly competitive environment, a lucrative market selection process is very important to the success of any business organization. In this context, the choice target market selection represents one of the most important functions to be performed by the division exporters. Target market selection is a multi-criterion problem which includes both qualitative and quantitative criteria. A trade-off between these tangible and intangible factors is essential in selecting the best target market. Proposed approach is based on fuzzy analytic hierarchy process (FAHP) and technique for order preference by similarity to ideal solution (TOPSIS) methods. FAHP method is used in determining the weights of the criteria by decision target market and then rankings of the target market are determined by TOPSIS method. Key words: Target market, analytic hierarchy process (AHP), technique for order preference by similarity to ideal solution (TOPSIS), fuzzy, saffron.

Purpose - The purpose of this study, Borsa Istanbul 100 (BIST100) of the financial performance of energy companies traded multi-criteria decision making methods, TOPSIS (Technique for order preference by Similarity to ideal solution) method is measured. Methodology - For this purpose, 5 energy companies traded in BIST in 2021 and whose data are regularly accessed have been included in the scope of the study. The annual balance sheet and income statements of the companies were used in the study. The balance sheets and income statements of the companies within the scope of the research for the year 2021 were taken from the official website of the Public Lighting Platform (KAP). During the period when the application part of this study was conducted, the data of the year 2022 could not be used due to the fact that the data of the year 2022 has not yet been published. The obtained data were measured by TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method, which is one of the multi-criteria Decisionmaking methods, and the performance of the companies were analyzed and compared among themselves. Findings - Ipek Natural Energy Resources Research and Production A. One of the companies included in the study as a result of the analyzes performed by the TOPSIS method.Sh. ((IPEK) was found to be the company with the best data in terms of financial performance in the analyzes carried out in accordance with the criteria included in the evaluation. After this company, the second best company in terms of financial performance is Koza Anadolu Metal Madencilik Işletmeleri A.Sh. He appeared as a (COCOON). Conclusion - In the light of the analyzes carried out in the study; IPEKE company ranked first as the best company in terms of financial performance. Ardın KOZAA of IPEKE company ranked second, ASELS company ranked third, AKSEN company ranked fourth and VESTL company ranked last in terms of financial performance among the 5 companies included in the study. Dec. Apart from these data, it can be said that changing the December period to be based on different studies, using different financial ratios, the degree of importance given to criteria, using other multi-criteria decision-making methods (MSCS) such as MOORA other than TOPSIS may give results that may change the performance ranking. Keywords: BIST-100, TOPSIS, financial performance, energy, MCDMM JEL Codes: C61, M41, M49

Supplier of a company increases its own economic strength and profitability. Speed of production, quality and cost of the product are some of the main goals of the companies to optimize. The multi-criteria aspect of the decision process of a company, including the supplier selection, increased the complexity of the management process. In this study, the methods for selection of suppliers for a company located in Bosnia and Herzegovina (BiH) are analyzed. The methods analytic hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS) algorithms are used together to analyze the company’s decisions. Assessments have been done and at the end of the study the strengths and the weaknesses of the two-phase AHP and TOPSIS are discussed. Key words: Multi-criteria decision process, supplier selection, analytic hierarchy process (AHP), technique for order preference by similarity to ideal solution (TOPSIS).