High Sound Insulation Research Articles

Comparison of sound insulation performance between closed-cell foam and automotive carpet

In developing sound insulation materials for automobiles, multiple sound insulation and sound absorption materials are laminated to achieve high performance. Generally, steel sheets, needle felts, and carpets are used to create sound insulation properties. In a luxury car, multiple layers with sound absorption and sound insulation properties are placed on the carpet to add higher sound insulation properties, but this increases the mass of the carpet. To solve this problem, we are investigating the the potential to realize both lightweight and high sound insulation properties using closed-cell form. In this study, we experimentally evaluated the sound transmission loss of closed-cell foam by comparing it with those of carpets with the same configuration used in standard and luxury cars.Furthermore, a numerical study is conducted. As a result, the closed-cell foam obtained higher sound transmission loss than the automobile specification carpet in a wide frequency range from 400 Hz to 5000 Hz. On the other hand, the sound transmission loss decreased by the same degree for both the automotive carpets and the closed-cell foam at 250 Hz.

Plate-type metastructure with low-frequency sound insulation and high stiffness properties

According to the mass law, it is impossible to increase sound transmission loss (STL) of conventional structures at low frequencies without increasing their weight. Metastructures are capable to break the limits of the mass law at low frequencies. However, many existing sound insulation metastructures need to be constructed using a host structure with low-stiffness properties, such as a thin plate and a thin membrane. As a result, the metastructures normally have large exposed areas with low-stiffness characteristics and are unable to bear heavy loads, which limits their practical applications. In this work, we propose a high-stiffness plate-type metastructure (HSPM) with both low-frequency sound insulation performance and high stiffness properties. The STL performance of the HSPM is demonstrated analytically, numerically and experimentally, indicating that the HSPM can deeply break the mass law at low frequencies. Owing to the simple construction, high stiffness properties, and high sound insulation performance at low frequencies, the proposed HSPM has promising applications in practical noise control engineering.

Improving low-frequency sound transmission loss of double panels with a plate-type acoustic metamaterial

The sound insulation performance of double-leaf partitions is crucially affected by the mass-air-mass resonance phenomenon, whose frequency reduction can shift the high sound insulation to lower frequencies. In this work, an alternative strategy for exceeding the low limit of the mass-air-mass resonance frequency of conventional double panels is proposed in terms of the effective surface mass density. An equivalent spring-mass model based on the effective medium theory is implemented to intuitively understand the characteristics. A simple double-panel metamaterial is designed by replacing one of the panels with a single-plate metamaterial attached strip masses to decrease the structural complexity. The extended semi-analytical method is applied to predict efficiently the sound transmission loss in the low-frequency range, which is verified by the coupled vibro-acoustic finite element method with excellent agreement. The results demonstrate that the proposed double-panel metamaterial can reduce the minimum of the resonant frequency without changing the areal mass density and panel spacing. The sound insulation can be significantly improved between the reduced mass-air-mass resonance and the anti-resonance frequencies. To provide a better understanding of the sound transmission loss improvement, parametric studies are conducted. The design strategy is validated through experiments conducted in an impedance tube, and the results corroborate the findings. This study is instrumental in designing double-panel partitions that require sound insulation in specific low-frequency regions.

Sound insulation enhancement of polyvinyl butyral film by blending polyurethane and its laminated safety glass

Laminated glass based on PVB film is widely used in military industry and life depending on its excellent safety performance. However, the insufficient sound insulation performance of PVB film restricts its practical application and has gained much more attention. In this work, a PVB-TPU composites with high strength and excellent sound insulation acoustic performance was designed by melt blending method which is attributed to their molecular entanglement and hydrogen bonding interactions between PVB and TPU molecule chains. It has been showed that the maximum tensile strength and elongation at break of the PVB-TPU blending film reached 34 MPa and 235 % respectively when 10 wt% content of TPU in the system. In addition, 20–41 dB of the sound transmission loss (TL) for the composite film with 1 mm thickness in the range of 2000–6000 Hz was achieved, which was obvious enhanced compared with the existing laminated glass intermediate film. The high impact resistance of the laminated glass based on the PVB-TPU film was confirmed by the falling ball impact test. The high sound insulation and safety laminated glass prepared here will be widely used in more fields.

A convenient approach to manufacturing lightweight and high-sound-insulation plywood using furfuryl alcohol/multilayer graphene oxide as a shielding layer

ABSTRACT With the requirement of green construction, the building envelope system urgently needs lightweight material with high sound insulation performance. In this study, a kind of plywood with furfuryl alcohol/multilayer graphene oxide (FA/MLGO) layer was prepared by lamination. The four-microphone impedance tube method measured the sound insulation to evaluate optimal process parameters. At the same time, the acoustic impedance, damping performance, interface microstructure, and chemical components were characterized to discuss the sound insulation mechanism of FA/MLGO as a shielding layer. It showed that the weighted transmission loss of plywood with different FA/MLGO layers was enhanced, and acoustic impedance increased while the acoustic radiation damping coefficient decreased. In addition, considering economic costs, the optimal preparation process was three layers with 0.5 wt.% MLGO concentration and 50 wt.% FA concentration, followed by curing for three h. The surface properties, micromorphology, and chemical composition results indicated that FA/MLGO layer formed more complex sound propagation paths in the plywood, thereby increasing the loss of sound energy inside. Thus, the sound insulation of the plywood was improved.

Membrane-type acoustic meta-material-based low-frequency noise reduction design and verification for transformers

In order to effectively reduce the radiated transformer noise, high sound insulation membrane-type acoustic meta-materials is designed based on CAE method and the main noise reduction frequency is typical 100Hz to make the maximum noise reduction of transformer. After a scale-reduced 500kV transformer semi an-echoic room noise tests comparison, the results show that the membrane-type acoustic meta-materials effectively suppressed the tonal noise of the transformer, providing a solid application foundation for the noise reduction design of transformer in the future.

Modular reverse design of acoustic metamaterial and sound barrier engineering applications: High ventilation and broadband sound insulation

A multi-gradient cavity acoustic metamaterial (MCAM) structure and a modular reverse design method (MRDM) that can realize high ventilation and broadband acoustic isolation are proposed. The method controls the deep neural network model of acoustic metamaterials through a particle swarm algorithm, and the optimized multi-gradient cavity acoustic metamaterial structure (OMCAM) can be reverse-designed by inputting only the constraints and the objective function such as the amount of noise reduction. Compared with the finite element method, the computational efficiency can be improved by about 500 times to achieve an optimized design. The acoustic simulation results show that the average noise reduction of the structure is 23.5 dB in the range of 0∼4000 Hz, and a broadband sound attenuation with 38 dB noise reduction is formed in the target frequency band of 500Hz∼2000 Hz. The acoustic experimental results of the 3D-printed structure are in agreement with the simulation results. Compared with the two existing ventilated acoustic metamaterials, the average noise reduction of OMCAM under equal ventilation capacity is improved by 10.6 dB and 17.4 dB, respectively. The sound barrier based on the proposed OMCAM design is implemented on an elevated rail transit line, showing an improvement of 9.4 dB of average noise reduction compared with existing upright railroad sound barriers. The noise reduction mechanism of the OMCAM structure was finally revealed by the sound field distribution in different modes.

Preparation and application of high sound insulation polyurethane composite film through glass fiber reinforcement

AbstractLaminated glasses have been widely used in buildings, physical protections, and vehicles because of their safety, sound insulation, thermal insulation, and other performance. In recent years, the high sound insulation performance of laminated glass intermediate films in the frequency range of low or high frequencies has attracted more and more attentions. In this work, a glass fiber/polyurethane elastomer composite (PU‐MGF) film with high transparency and impact resistance has been successfully synthesized, 5 dB of the transmission loss increased at 1600–6000 Hz, and 3.6 dB increased at 63–1600 Hz compared with the control polyurethane film. This is a significant progress in the laminated glass industry. In addition, the transmittance of the composite reaches over 75%. The excellent impact resistance of the laminated glass, based on PU‐MGF film, has been confirmed through falling ball impact test, demonstrating its ability to withstand multiple impacts without spattering. The PU‐MGF film prepared in this work exhibits great potential for applications in building windows, transportation, and soundproof devices.

A lightweight and transparent acoustic metamaterial sheet with designed structures for sound insulation applications

Normal sound insulation materials such as metal plates and rubber sheets follow the mass law. According to the mass law, a weight increase of sound insulators leads to high sound insulation. Therefore, novel lightweight and high-performance materials have been required in various fields such as mobility and electronics. We developed lightweight and transparent acoustic metamaterial sheets having blocklike weights with rodlike or cylindrical shapes periodically arranged on thin films. Upon sound incidence at a target frequency, the heavier weights and the lighter film cooperatively vibrate in opposite phase and with the same amplitude. The transmitted sound waves through those parts cancel each other out owing to the wave interference. As a result, the acoustic metamaterial sheets show high sound insulation performance beyond the mass law limit at the target frequencies. In this study, we report the structural design, sound insulation properties and mechanisms, and application of acoustic metamaterial sheets.

Study on Heavy Weight Impact Sound Insulation of CLT Floor Slab and Reduction Performance with Floor Structure

Strategies and challenge for carbon neutrality by 2050 had become important issues all over the world. In South Korea, as a move toward carbon neutrality, interest in wooden buildings is growing continuously. In order to spread the wooden buildings, especially wooden multi-residential buildings, high floor impact sound insulation performance is required. In this study, we investigated the floor impact sound insulation performance of floor slabs with cross laminated timber (CLT) panels produced in South Korea. Moreover, laboratory measurements were conducted to grasp the reduction effect by floor covering. As a result, the heavy-weight impact sound insulation performance of CLT bare slab of its thickness of 150 mm is almost 17 dB lower than that of RC slab according to ISO717-2. Concrete topping and damping material are found to be effective to both heavy and light weight floor impact sound insulation.

Current Performance of Floor Impact Sound Insulation in Wooden Apartment Buildings in Hokkaido

In Hokkaido, Japan, technological developments have been introduced to improve the floor impact sound insulation performance in wooden apartment buildings. However, such technological developments are not widely used, especially in rental properties. To effectively disseminate the required technology, it is vital to report examples of implementation. Therefore, we measured the performance of five types of wooden apartment buildings with high sound insulation performance and analyzed the results. The main results are listed below. (1) A relatively high performance was obtained by installing a floating floor and an independent ceiling. (2) For heavy weight floor impact sound insulation of a car tire source, a floating floor with a surface density of 60 kg/m2 or higher could achieve a performance of Li,Fmax,r,H(1)-60 or higher. However, in the case of a rubber ball source, vibration radiation noise from the wall surface of the lower floor is large, so it is necessary to consider vibration countermeasures. (3) For light weight floor impact sound insulation, sufficient performance cannot be obtained even with a floating floor. Therefore, carpet or wooden soundproof flooring should be used. (4) The light weight floor impact sound pressure level is high when the floor area of the sound receiving room is small.

Sound insulation enhancement of PVB film by additive engineering

In recent years, noise pollution has become a prominent topic in the energy field. The lightweight and high sound insulation materials have attracted more and more attentions. This study focuses on improving the sound insulation properties of PVB films by adding a little water during the processing. When the water content was 4 %, the average sound transmission loss improved by 5.7 dB at 500–1100 Hz, with a maximum improvement of 17.6 dB, due to porous structure formed by the water additives. Meanwhile, the tensile stress was 28.1 MPa and the elongation at break achieved 140.4 %, which were 1.06 and 1.24 times higher than that of PVB without water, respectively. The porous structure and sound insulation mechanism for PVB films were characterized by SEM, BET and acoustic impedance tubes, etc. .1

ПОРЫ ВОЗДУХОВОВЛЕЧЕНИЯ В СТРУКТУРЕ ГАЗОБЕТОНА

Aerated concrete is one of the most popular building materials, which has unique properties such as light weight, high sound and heat insulation characteristics and strength. However, its porous structure may reduce its strength and durability. In this article, the author examines the various types of pores in aerated concrete and their effect on its properties. Gel and capillary pores are the main types of pores that are formed during the production of aerated concrete. Air (gas) pores are formed as a result of a chemical reaction between gas and binder. They also affect the properties of aerated concrete, but to a lesser extent than gel and capillary ones. However, air entrainment pores negatively affect the quality of aerated concrete. This type of pore is formed when pouring an aerated concrete mixture and represents air bubbles that reduce the strength of the material and impair its thermal insulation properties. To improve the quality of aerated concrete and prevent the formation of air entrainment pores, it is necessary to optimize production technologies and control the pouring process. The article also discusses the features of the formation of an air entrainment pore and the transformation of the shape of entrained air in an air entrainment pore with the shape of an inverted drop.

Effects of Carbon Nanotubes on Thermal Behavior of Epoxy Resin Composites

Human society’s need to build low-weight, high-strength and durable structures has increased the demand for composite materials. In this case, composites are used where high mechanical strength, low weight, sound and thermal insulation properties are required. One of the most important issues now is designing materials and coatings aimed at reducing heat loss and resisting high temperatures. One way to address this problem is to develop a technique for preparing and applying composite materials that slow down their heating applied to a surface. In this study, carbon nanotubes (CNTs) reinforced composites were fabricated using silicone molding to be applied to honeycomb sandwich structures. To determine the effect of CNTs on the thermal behavior of the sandwich panels, different weight percentages of this material (0.025, 0.05. 0.075 wt.%) were added to the epoxy resin. The results showed that the thermal stability of the epoxy composites was directly related to the increase in the percentage of CNTs as the CNT content increased to 0.075 wt.%, and the thermal degradation temperature of the epoxy composites increased by 14 °C. In addition, the energy absorption increased by 4.6% with an increase in CNTs up to 0.075 wt.%. Density measurements showed that the density of the nanocomposite samples increased by adding CNTs to pure epoxy resin. The actual densities of the samples reinforced with 0.025, 0.05, and 0.075 wt.% CNTs are 0.925, 0.926, and 0.927 of the theoretical density, respectively. Since the CNT dispersion uniformity in the epoxy matrix can significantly affect the properties of the composites, in this study, a new method of dispersing CNTs in the epoxy resin matrix resulted in higher thermal conductivity while using lower amounts of CNTs compared to other studies. The storage modulus of the epoxy matrix composites reinforced with 0.05 wt.% in this study was 25.9% and 6.9% higher than that from the previous study reinforced with 0.1 wt.% and 0.25 wt.% CNTs, respectively. Furthermore, the tanδ and loss modulus of the composite reinforced with 0.05 wt.% CNTs in this study were 52% and 54.5% higher than that from the previous study with 0.1 wt.% CNTs, respectively. This study provided an optimal approach for designers and engineers who want to effectively design their composite honeycomb sandwich structure with better thermal properties.

Study on sound insulation performance of sonic black hole with micro-perforated plates

According to the traditional law of mass, the insulation of low-frequency sound usually requires thick, high-density materials. However, lightweight metamaterials containing acoustic structures can also achieve high acoustic transmission losses. In this study, we present a sonic black hole (SBH) device coupled with micro-perforated plates (MPPs) and intraluminal column structure to achieve high sound insulation performance with light weight. The finite element model (FEM) is developed to analyze the acoustic energy distribution and dissipation inside the SBH device to evaluate its sound transmission loss (STL), and the accuracy of the analytical model is verified by impedance tube testing. The analysis results show that the SBH device has excellent sound insulation performance in the broadband and low frequency mainly due to the energy dissipation caused by the MPPs and column structure, and wavelength compression, energy focusing caused by the SBH effect. Finally, the sound insulation capacity of SBH can be further improved by improving the structure, such as increasing the complexity of acoustic medium flow and adding the number of layers of MPPs. The numerical model and the calculation results of this paper provide a new way of thinking for the design and optimization of SBH sound insulation structures.

INCREASING THE ACCURACY OF DEFECTOSCOPY BY THE METHOD OF ACTIVE THERMOGRAPHY OF PRODUCTS MADE OF NON-METALLIC HETEROGENEOUS MATERIALS AND USED IN ENGINEERING

Nowadays, non-metallic heterogeneous materials are widely used in mechanical engineering, which is primarily due to their unique properties, such as strength, light weight, corrosion resistance, and high vibration, sound, and heat insulation characteristics. At the same time, non-destructive control methods that would allow to obtain the most complete picture of the defective state of products made of such materials are of great importance. The main task of the work is the development of optimal algorithms for determining each defect of a product made of non-metallic heterogeneous material with the establishment of its exact location, including the depth of occurrence, as well as its geometric parameters. The method of thermal non-destructive testing is considered promising. Studies of the accuracy of determining the parameters of defects in non-metallic heterogeneous materials by the specified method have been carried out.

Study of acoustic transmission losses in particle-reinforced rubber-based membrane-type acoustic metamaterials

In this work, the mechanical properties of particle reinforced ethylene propylene diene monomer (EPDM)/ethylene tetrafluoroethylene (ETFE) copolymer material were determined by molecular dynamics (MD) method, and the copolymer material was used in the structural design of acoustic metamaterials. Secondly, based on the discrete point matching method, the acoustic transmission loss characteristics of the material are predicted, and the accuracy and effectiveness of the theory are verified through the multi physical field coupling finite element model. Finally, seven key parameters that affect the material structure are studied, and their influencing rules and mechanisms are analyzed. The results show that the structure makes up for the sound insulation defect of traditional ETFE film materials at low frequencies. Through reasonable selection of key parameters, high sound insulation design can be carried out for specific frequency bands, which is of great significance to the potential application in the construction field (new building materials).

Low-frequency sound insulation of honeycomb membrane-type acoustic metamaterials with different interlayer characteristics

The membrane-type structure that can achieve excellent sound insulation characteristics under lightweight conditions is widely concerned, but it generally involves a small mass block attached to a thin membrane. Although this kind of design can obtain better acoustic insulation performance, the mass block will cause installation and manufacturing issues in industrial applications. This paper presents a multilayer honeycomb membrane-type acoustic metamaterial with an interlayer structure. Similar to the mass block, the interlayer structure makes less sound energy transmitted by varying the eigenmode characteristics of the membrane. Considering the integrated design of the interlayer structure, the issues of installation and manufacturing are solved and the sound transmission loss is enhanced on the fixed overall dimension and small additional mass. The results indicate that the design of interlayer structures can break the bottleneck of ultrathin and lightweight requirements. Meanwhile, the symmetry of interlayer position can lead to the shift in transmission loss valley to a higher frequency, achieving high sound insulation in a wide frequency range.

Low frequency sound insulation of membrane-type acoustic metamaterials with negative pressure cavity

The membrane-type acoustic metamaterial with negative pressure cavity (MAM-NPC) is designed to achieve low frequency sound insulation and tunable frequency on the duct side wall. A one-dimensional analytical method was used to discuss the sound insulation effect of MAM-NPC on the sidewall of the duct. As the negative pressure increases, the first valley of sound insulation moves to high frequency. High sound insulation can be achieved in the low frequency range. The theoretical and finite element method results are compared. The one-dimensional analysis method basically agrees with the finite element results in the low frequency band. Because only plane waves are considered in the one-dimensional analytical method.

Thermal and acoustic insulation properties in nanoporous geopolymer nanocomposite

In building and construction sector, seeking for high thermal and sound insulation materials is crucial to reach lower carbon footprints and also for curtailed consumption energy either for heating or for cooling. Nowadays, geopolymer nanocomposites, an alternative binder to Ordinary Portland Cement (OPC), are drawing considerable attention for their great prospective to withstand heat and sound exposure beside to their outstanding properties including high early strength, little creep and shrinkage and a good resistance to corrosion and abrasion. To advance geopolymer insulating properties, a nanoscale analysis has been investigated here to consider porosity, nanopore size, moisture as well as chemical composition and alkali agents impacts. Our findings conclude that a better thermal isolation is predicted for a high-silicon content geopolymer nanostructure with the presence of sodium alkali activators. The lowest thermal conductivity values of 0.08 W/m.K and 0.10 W/m.K are obtained for a porosity of 30.8% for Na+ and K+ samples, respectively. Considering humidity, results indicate that residual water enhances 4.5 times the thermal insulation of a highly nanoporous metakaolin geopolymer rich on silicon and in the presence of NaOH alkali activator. Nanoscale investigation has finally shown a promising acoustic insulation behavior than OPC material when pore size and porosity are higher than 12 Å and 20% respectively, making nanoporous geopolymer paste as a great challenge for cementitious materials.