Resonant Sound Absorption Research Articles

Experimental and numerical investigation of soundproof panels using acoustic metamaterials with porous material

Acoustic panels are often used in buildings and automobiles. For sound absorption in panels, high sound absorption performance in a wide frequency band can be achieved by combining porous sound absorption, resonant sound absorption, vibration sound absorption, and acoustic metamaterials. This study proposes a highly sound-absorbing panel structure by using an acoustic metamaterial that generates local resonance to a double-walled structure filled with porous material. In the soundproof panel of this study, local resonance is generated by a structure in which slits are made in a porous material. By the through-holes of the slits, local resonance occurs, but sound leakage and thermal viscosity in the slits may affect the sound absorption effect. Therefore, in this study, sound transmission loss for various cases with differing factors such as the use of porous materials, the presence of spiral slits, and layer configurations are compared through the acoustic analysis and experiments. The results substantiate that the proposed panel structure has high soundproofing performance in wide frequency ranges, each driven by distinct physical principles.

Research on noise reduction methods for indoor substations based on resonant sound absorption

Aiming to reduce the impact of substation noise on the lives of surrounding residents, improving the low and middle frequencies acoustic performance of traditional resistive mufflers in indoor substations is significant. The paper is based on the resonance sound absorption mechanism, and for the first time applies multi-frequency resonance noise reduction technology to the research field of indoor substation noise control, proposing a multi-frequency resonant muffling structure. The acoustic performance of the proposed muffler unit is investigated through theoretical and numerical analysis. The measured noise data of the indoor substation is used as sound excitation in the numerical analysis. The results show that at frequencies of 100 Hz, 200 Hz, 300 Hz, 400 Hz, and 500 Hz, the noise in indoor substations is significantly reduced by the multi-frequency resonant muffling structure. The paper provides references for the application of multi-frequency resonant mufflers in the field of noise control of indoor substations.

Study on Sound Absorption Properties of Polyvinyl Chloride (PVC) Film Multicavity Structure Materials

Since the development of industry, sound absorption and noise reduction have gradually become an urgent problem to be solved. Lightweight polymer film materials are very effective in response to sound waves, and sound waves can easily cause vibration of the film, which can convert sound energy into vibration and film friction to achieve sound absorption. The application conditions of the film material are very harsh, that is, a support body is required to fix the film and the film needs to be tensioned. The film is very thin and easy to damage. The idea of this research is to transform the film into a bubble structure and use a large number of film bubbles to form a cavity structure material. As a unit of the sound absorption structure, bubbles can avoid damage to the film. In this paper, commercial polyvinyl chloride film bubble materials are used to prepare two kinds of film multicavity structure materials, and the sound absorption performance of this film multicavity structure material is studied. The research results show that this film multicavity structure material has very excellent broadband sound absorption performance, which changes the narrow band sound absorption properties of the usual film single cavity. The average sound absorption coefficient can reach 0.84 in frequency range from 500 Hz to 6400 Hz. This structural material has a single peak sound absorption curve at the middle and low frequency bands, which is the characteristic of resonance sound absorption. And at the middle and high frequency bands, it exhibits the characteristics of broadband sound absorption. The film multicavity structure material has both cavity sound absorption and broadband sound absorption characteristics.

Sound attenuation analysis of a honeycomb structure with extended necks

In this paper, a honeycomb structure metamaterial consisting of 95 necks that are attached to the perforated top panel is presented and its sound absorption coefficient and transmission loss are investigated using the finite element method. Helmholtz resonators are therefore created by each honeycomb cell (cavity) and the attached neck, which is protruding within each cell. The structure has therefore a high bending stiffness due to the honeycomb mechanical performance and constitutes a sound absorber based on the parallel assembly of multiple Helmholtz resonators. This study demonstrates the importance of properly designing the diameter and the length of each neck to create a broadband sound absorption. One resonant sound absorption peak is observed when all the necks are identical, and two absorption peaks are obtained using two different sets of neck parameters. When the number of different necks increases, the sound absorption frequency band improves and when the parameters of all the necks are different, resulting in a parallel assembly of 95 different Helmholtz resonators, the sound absorption frequency band broadens. The material design studied in this paper can be useful in various applications where available space is limited and high mechanical stiffness and noise reduction are required in one structural element.

Highly efficient underwater acoustic absorber designed by filled-microperforated plate-like structure: Aging and life prediction

The underwater sound absorption material for submarines should fulfill the demand for remarkable performance in medium-low frequency sound absorption at low thicknesses. Hence, in this paper, the innovative “filled-microperforated plate-like” (F-MPPL) structure was introduced to the hollow microballoons filled underwater sound absorption composite (HBF composite) using the tailor-made 3D spacer fabric. The test results show remarkable mechanical properties with a compression strength and compression modulus of 2256 KPa and 14.6 MPa for the new type of F-MPPL composite, respectively. In addition, the peak sound absorption coefficient of the F-MPPL composite reaches 0.77 at just 7.5 mm thickness based on the resonant sound absorption characteristic introduced by the F-MPPL structure. Moreover, the study investigated the effects of seawater aging on the F-MPPL composite and found that while there was a decrease in compression strength and average sound absorption coefficient, the degradation of the F-MPPL composite was significantly smaller than the HBF composite due to the inhibitory effect of spacer yarns on pore expansion. Finally, this study proposed the method of using compression strength to predict the long-term life of the F-MPPL composite under seawater aging, and a 60% retention rate after 20 months was displayed.

Sound absorption performance of micro-perforated plate sandwich structure based on triply periodic minimal surface

The sandwich structure based on Triply periodic minimal surface (TPMS) is a lightweight and high-strength multifunctional composite material that combines the versatility of heat exchange, impact resistance, and energy absorption, and has been widely used in various fields such as aviation and aerospace. However, its sound absorption performance has not meant fully studied. In this paper, a Micro-perforated plate Diamond sandwich structure (MPP-DSS) was designed based on TPMS method, which was composed of aluminum alloy solid panel, aluminum alloy macroscopically ordered porous Diamond structure and aluminum alloy micro-perforated plate. The acoustic absorption performance in low and medium frequency band was studied by impedance tube method. The results show that MPP-DSS has higher absorption coefficient and bandwidth than traditional perforated plate structure with the same structural parameters. Increasing the thickness of micro-perforated plate can improve the sound absorption capacity of MPP-DSS in the low frequency range, but the width of the sound absorption band will be narrowed accordingly. Different from the resonant sound absorption mechanism of the traditional perforated plate structure, the sound absorption mechanism of MPP-DSS is the combined effect of resonant sound absorption and friction loss sound absorption. This study broadens the versatility of the TPMS structure and can serve as a reference for the design of integrated load-bearing and sound-absorbing structures.

Fabrication of one-step shape memory gradient sound absorber with wrinkled inner wall and closed-pore structure

Plastic foam sound-absorbing material is of great significance to improve indoor sound environment. However, since the preparation of foamed material is fundamentally induced to form a homogeneous pore structure, the sound absorption frequency range is relatively narrow, limiting the sound absorption performance to a great extent. In order to improve the sound absorption performance in a wide frequency range, this work designed the combination of macro-porous gradient foam (MGF) and closed-pore resonator, introduced part of polyimide (PI) components based on the one-step free foaming method of polyurethane foam (PUF), and proposed a straightforward route to prepare basic polymer gradient foam. Through the arrangement and combination of different bubble holes, the sharp hole structure and the Helmholtz resonance structure were constructed by analogy. Importantly, the internal structure of the foam system was reorganized under the action of surface tension due to the inward collapse of the viscous bubbles during the process of bursting, resulting in the formation of wrinkled structures and small bubbles, which enhanced the resonant sound absorption at lower frequencies. In 200–6400 Hz, the MGF1 sample had the highest sound absorption capacity, with a cavity size range of 8.27–4.14 mm and the ability to absorb 90% of the acoustic wave above 1100 Hz. In addition, MGF samples also exhibited heat insulation behavior (0.047–0.061 W/(m·K)), shape memory, and energy absorption capacity. This gradient compound resonance structure satisfies the convenience of process manufacturing and high-efficiency sound absorption performance, which is essential for the wide application of plastic foam sound-absorbing materials.

Research on Sound Absorption Properties of Tri-Periodic Minimal Surface Sandwich Structure of Selective Laser Melting Titanium Alloy

Triply Periodic Minimal Surface (TPMS) sandwich structure has the characteristics of lightweight, high specific strength, specific stiffness, vibration, and noise reduction. There is relatively little research on its sound absorption performance. TPMS sandwich structure based on selective laser melting (SLM) technology can achieve precise control of structure type, porosity, and so on, and has broad prospects in noise control applications. In this paper, the sandwich structure is designed based on tri-periodic minimal surface implicit function, and the titanium alloy sandwich structure is formed by SLM technology, and the sound absorption performance of titanium alloy TPMS sandwich structure is studied. The effects of volume fraction, panel thickness, and cell layer number on the sound absorption performance of the two TPMS structures were systematically analyzed using the transfer function method. The results show that: The GP10 sandwich structure with the volume fraction of 20%, the thickness of the panel is 1.0 mm, and the number of cell layers is 3C parameter combination has better sound absorption performance and higher sound absorption bandwidth, and the sound absorption coefficient is 0.36. For Ti6Al4V sandwich sound absorption structure, it is not suitable to design too thick panels. When the volume fraction is lesser, the increase of the tortuosity factor τ improves the sound absorption performance of the two structures, and excessive volume fraction leads to a decrease of sound absorption performance. The increase of cell layers can broaden the sound absorption bandwidth of the two structures, and the sound absorption capacity increases and then decreases in the range of 150–6400 Hz. The Gyroid structure mostly exhibits resonance sound absorption mechanism, while the Diamond structure exhibits resonance sound absorption mechanism combined with the viscous loss of sound wave. The work done in this paper can provide a theoretical basis for the study of the sound absorption characteristics of TPMS sandwich structure.

Design and Fabrication of Double-Cavity Resonant Structure toward Low-Frequency Sound Absorption Improvement

Exploring broadband sound-absorption technology is of great significance in acoustics, with wide applications in noise control and sound mitigation. In this work, a multiband sound-absorbing device was proposed with two air cavities. A double resonant structure was constructed by embedding a sound-absorbing material in the Helmholtz resonator’s neck and a microperforated board inside the Helmholtz resonator, respectively. In particular, we systematically discussed the sound absorption coefficient of each assembly unit and shed light on the mechanism and structure-activity relationship of the proposed double-cavity resonant device (DCRD). The results showed that the sound absorption performance of the prepared DCRD was about twice higher than that of the Helmholtz resonance structure under the same air cavity content. Thus, it could greatly improve the absorption ratio of low-frequency sound without sacrificing high-frequency performance with the microperforated plate assistance. Overall, we believe this work provides a new toolbox to enrich the family of resonant sound absorption materials, especially realizing noise reduction optimization of low-frequency sounds through a flexible design approach.

Highly efficient acoustic absorber designed by backing cavity-like and filled-microperforated plate-like structure

Crowded living conditions and increasingly severe noise problems necessitate the development of a low-thickness sound absorption material with remarkable sound absorption performance. Here, simple materials such as sodium alginate aerogel (SA) and polyurethane (PU) foam are used to combine with special 3D spacer fabric to design an innovative highly-efficient acoustic absorber composite (B&M−L composite). It integrates a “backing cavity-like” (BC-L) structure and “filled-microperforated plate-like” (MPP-L) structure. Thereby, it realizes porous and resonant sound absorption at a small thickness. The superior structure design combining strong resonance with porous structure endows the new type of composite with a remarkable absorption performance. Specifically, the peak absorption coefficient is 0.98, the average absorption coefficient at a thickness of 10 mm is 0.71, and the noise reduction coefficient per unit thickness of B&M−L composites exceeds those of most of the reported sound absorption materials. Based on its remarkable acoustic performance, good mechanical properties, heat insulation performance, and thermal stability, the B&M−L composite provides a convenient and inexpensive method to improve the overall performance of porous sound absorption materials, and displays significant potential for use in the fields of construction, transportation, and large mechanical equipment.

Sound absorption properties of nanofiber membrane-based multi-layer composites

Aiming at the problem of poor low-frequency sound absorption performance of traditional fiber sound-absorbing materials, this work prepared nanofiber membrane-based multi-layer composites by lamination for sound absorption and noise reduction. By laminating polyvinyl butyral (PVB) nanofiber membrane with polyester (PET) fiber felt and polyurethane (TPU) film, bi-layer and three-layer composites structure sound-absorbing materials were manufactured, and the effect of lamination sequence and thickness of each layer on their sound absorption performance were investigated. The results testified that the composite structures have excellent sound absorption performance in low-frequency range while the nanofiber membrane was placed at the sound-facing surface. When the thickness of PVB was 2 mm, and the thickness of PET was 10 mm, the average sound absorption coefficient of PVB-PET structure composite reached 0.5646 in the low-frequency range. Notably, the frequency and peak of the first resonance sound absorption peak were 396 Hz and 0.8529, respectively, which can meet the needs of sound absorption and noise reduction. Another layer of TPU film was compounded on the backside of this structure, and the sound absorption peak was further transferred to the low-frequency range. The frequency and peak of the first resonance sound absorption peak of the three-layer composite structure material were 300 Hz and 0.7772, respectively. Compared to 10 mm thick PET fiber felts, the average sound absorption coefficients of both bi-layer and three-layer composite materials were improved by more than 200 % in the range of 100–1000 Hz. Additionally, the results of response surface optimization illuminated that the sound absorption of different frequency bands can be targeted through reasonable selection and optimization of structural parameters.

Research Progress on Sound Absorption of Electrospun Fibrous Composite Materials.

Noise is considered severe environmental pollutant that affects human health. Using sound absorption materials to reduce noise is a way to decrease the hazards of noise pollution. Micro/nanofibers have advantages in sound absorption due to their properties such as small diameter, large specific surface area, and high porosity. Electrospinning is a technology for producing micro/nanofibers, and this technology has attracted interest in the field of sound absorption. To broaden the applications of electrospun micro/nanofibers in acoustics, the present study of electrospun micro/nano fibrous materials for sound absorption is summarized. First, the factors affecting the micro/nanofibers’ sound absorption properties in the process of electrospinning are presented. Through changing the materials, process parameters, and duration of electrospinning, the properties, morphologies, and thicknesses of electrospun micro/nanofibers can be controlled. Hence, the sound absorption characteristics of electrospun micro/nanofibers will be affected. Second, the studies on porous sound absorbers, combined with electrospun micro/nanofibers, are introduced. Then, the studies of electrospun micro/nanofibers in resonant sound absorption are concluded. Finally, the shortcomings of electrospun micro/nano fibrous sound absorption materials are discussed, and the future research is forecasted.

Fabrication of flexible sound absorption composite by constructing membrane with damping function on fabric

Noise, such as people talking, car whistle, tire friction, etc., affect people’s lives. In practical applications, curtains and wall coverings have sound absorption function to reduce noise annoyance is expected by people. In order to improve the sound absorption of the widely used woven fabric, a damping membrane was constructed on the fabric surface to prepare a flexible sound-absorbing composite material. Effects of fabric structure, constructed structure, membrane thickness, filler on the sound absorption of the composite were explored. From the results, the sound absorption of composite is caused by the porous sound absorption of the fabric, the damping and noise reduction of the membrane and the resonance sound absorption of the structure, which cannot be simply predicted by the model. When the membrane thickness of the structure was about 50 μm and the filler was vermiculite, the composite exhibited the best sound absorption performance: the sound absorption coefficient (α) reached 0.56, which was about 2.8 times that of the fabric. Moreover, the sound absorption bandwidth of the composite was nearly 1500 Hz wider than that of fabrics. This flexible composite material can be used as sound-absorbing products such as wall coverings, thin curtains and other products.

Micro-structural analysis of noise reduction mechanism of porous asphalt mixture based on FEM

PurposeIn order to give full play to the function of noise reduction of asphalt pavement, it is necessary to understand its internal sound absorption mechanism. Therefore, the purpose of this study is to establish a micro model of the pore structure of asphalt mixture with the help of finite element method (FEM), discuss the noise reduction mechanism of asphalt pavement from the micro perspective and analyze and evaluate the noise attenuation law of the pore structure.Design/methodology/approachThe FEM was used to establish the microscopic model of the pore structure of asphalt mixture. Based on the principle of acoustics, the noise reduction characteristics of asphalt pavement were simulated. The influence of gradation and pore characteristics on the noise reduction performance of asphalt pavement was analyzed.FindingsThe results show that the open graded friction course-13 (OGFC-13) has excellent performance in noise reduction. The resonant sound absorption structure composed of its large porosity can effectively reduce the pavement noise. For asphalt concrete-13 (AC-13) and stone matrix asphalt-13 (SMA-13), the less resonant sound absorption structure makes them have poor sound absorption effect. In addition, the variation rules of noise transmission loss (TL) curve and sound absorption coefficient curve of three graded asphalt mixtures were obtained. At the same time, the peak noise reduction values of OGFC-13, AC-13 and SMA-13 were obtained, which were 650Hz, 1000Hz and 800Hz, respectively.Originality/valueThe results show that the simulation results can well reflect and express the experimental results. This will provide a reference for further exploring the sound absorption mechanism and its variation rule of porous asphalt pavement. It also has some positive significance for the application of low noise asphalt pavement.

Sound-Absorption Performance and Fractal Dimension Feature of Kapok Fibre/Polycaprolactone Composites

This article introduces a kind of composite material made of kapok fibre and polycaprolactone by the hot-pressing method. The effects of volume density, mass fraction of kapok fibre, and thickness on the sound-absorption performance of composites were researched using a single-factor experiment. The sound-absorption performance of the composites was investigated by the transfer function method. Under the optimal process parameters, when the density of the composite material was 0.172 g/cm3, the mass fraction of kapok was 40%, and the thickness was 2 cm, the composite material reached the maximum sound-absorption coefficient of 0.830, and when the sound-absorption frequency was 6300 Hz, the average sound-absorption coefficient was 0.520, and the sound-absorption band was wide. This research used the box dimension method to calculate composites’ fractal dimensions by using the Matlab program based on the fractal theory. It analysed the relationships between fractal dimension and volume density, fractal dimension and mass fraction of kapok fibre, and fractal dimension and thickness. The quantitative relations between fractal dimension and maximum sound-absorption coefficient, fractal dimension, and resonant sound-absorption frequency were derived, which provided a theoretical basis for studying sound-absorption performance. The results showed that kapok fibre/polycaprolactone composites had strong fractal characteristics, which had important guiding significance for the sound-absorption performance of kapok fibre composites.

Broadband low-frequency sound absorption by coiled-up space embedded in a porous layer

Low frequency noise has strong penetration power and is difficult to be attenuated. In order to solve the problem of low-frequency noise absorption in traditional sound absorbing materials, a coupled structure of coiled-up space core embedded in a porous material (CSPM) is proposed. The coiled-up space core (CSC) structure consists of a folding structure and a labyrinth structure, and a rectangular slot is cut at the top of each structure to allow the sound wave to enter. The resonant sound absorption peak of CSPM is formed in the low frequency range and the sound absorption performance is achieved above 85% at 105 Hz and 90% at 315 Hz. The CSMPs which consists of four different parameters of CSC embedded in the porous layer, and its absorption performance can reach as high as 0.75 from 195 Hz to 600 Hz. The influences of the porosity, flow resistance, tortuous factor of porous materials and parameters of CSC on the sound absorption performance are also investigated. In this work, CSPM is fabricated and its sound absorption performance is tested through an impedance tube for verifying the correctness of the simulation.

Research on the Design of Sound Insulation Performance of Isolating-sound and decoupled tile Based on Local Resonance Membrane Material

In order to enhance the acoustic stealth performance of the underwater vehicle, we combine the resonance sound absorption and vibration suppression performance of the sound-absorption coating and the low frequency sound insulation performance of the local resonance membrane material, a new type of isolating-sound and decoupled tile with low-frequency sound insulation, sound absorption and vibration suppression performance is designed, and an acoustic enclosure composed of isolating-sound and decoupled tile is established. Research shows: the isolating-sound and decoupled tile cell has good sub-wavelength sound insulation ability, and the average sound insulation in the 100-1000Hz frequency band is 47dB. The acoustic enclosure composed of it can effectively isolate the reverberation sound field in the enclosure. Compared with the acoustic enclosure composed of Alberich sound-absorption coating, the average sound insulation has been increased by about 19dB.

Sound-absorption properties of composite materials containing waste-wool / polyamide fibers and their relationship with fractal dimensions

To solve the problems related to the recycling of waste fibers, composite materials were prepared by the hot-pressing method using waste-wool fibers and waste low-melting-point polyamide fibers combined into a net as the raw materials. The effects of the volume density, mass fraction of waste-wool fibers, and thickness on the sound-absorption properties of the resulting composite materials were studied by the controlling-variable method. The sound-absorption properties of the composite materials were studied by the transfer-function method, and under optimized technological conditions, the sound-absorption coefficients were above 0.8 and the sound-absorption bands were wide. According to the box-counting-dimension method, which is based on the fractal theory, the fractal dimensions of the composite materials were calculated using the Matlab program. The relationships between the fractal dimensions and the volume densities, mass fractions of waste-wool fibers, and thicknesses of the composite materials were also analyzed. Then, quantitative relationships between the fractal dimension and the maximum sound-absorption coefficient, and between the fractal dimension and the resonant sound-absorption frequency, which play a major role in the sound-absorption design of composite materials, were deduced.

Effects of structural design including cellular structure precision controlling and sharp holes introducing on sound absorption behavior of polyimide foam

This paper aims to effectively improve acoustic property of polyimide foam (PIF) by regulating cellular structure of PIF on a large scale and introducing sharp hole structure simultaneously, adopting a special mold with split structure in a closed-mold foaming route. In this work, PIF with same split structure but different pore cell sizes, density, and windows opening rate were produced in the first time. Due to the stepwise transition principle, the impedance of the air acoustic medium and the acoustic material was well matched. In addition, the characterization results showed the effectively effects of microporous structure and split structure characteristics of PIF on the acoustical absorption coefficient. For PIF-4, sound absorption coefficient kept around 0.9 from 900 to 6300 Hz. Especially, the resonance sound absorption characteristics was basically eliminated, which ensured the high efficiency sound absorption behavior of PIF in the broadband range from 600 to 6300 Hz region.

Utilization of hemihydrate phosphogypsum for the preparation of porous sound absorbing material

Phosphogypsum (PG) as an industrial by-product of phosphoric acid production causes severe environmental pollution. Beta-hemihydrate phosphogyspum (β-HPG) obtained by low temperature calcination of PG can be used for the preparation of functional building materials to achieve its utilization. This work aims to utilize β-HPG as raw material for the preparation of porous sound absorbing material (PSAM). The effects of pore-forming agent, basalt fiber and expanded perlite on the properties of PSAM were investigated systematically by the analyses of sound absorption coefficient, mechanical strength, bulk density, open porosity and microstructure. In addition, the sound absorption properties of PSAM were evaluated by noise reduction coefficient in accordance with the corresponding Chinese standard. The results show that pore-forming agent and basalt fiber can form a large number of interconnected pores in the PSAM, and expanded perlite can further increase the sound absorption properties of PSAM by the combination of interconnected pore structure and cavity resonance sound absorption structure. High efficiency sound absorbing material can be prepared with 0.6 wt% pore-forming agent, 1 wt% basalt fiber and 6 wt% expanded perlite by the weight of β-HPG. This work provides an effective and high value-added way for the utilization of PG.