Membrane-type Acoustic Metamaterials Research Articles

An investigation on synergistic resonances of membrane-type acoustic metamaterial with multiple masses

Membrane-type acoustic metamaterials (MAM) represent a class of materials that are lightweight, compact, structurally simple, and simultaneously offer flexibility and moldability, all while demonstrating exceptional sound attenuation properties in the low-frequency range. As a continuation, this study focuses on membrane-based acoustic metamaterials with synergistic resonance of multiple loaded mass blocks. By varying the unit shape, arrangement method, radius and material of the loaded mass blocks, the low-frequency sound insulation performance of membrane-based acoustic metamaterials with synergistic resonance of multiple loaded mass blocks was calculated using a numerical model that are experimentally validated. The results indicate that the peak transmiss loss (TL) frequencies can be tuned to specific values. The optimized membrane-type acoustic metamaterial could achieve a TL bandwidth up to 844 Hz (>5dB) and a TL bandwidth up to 376 Hz (>10 dB) within the low-frequency range. Acoustic-membrane analysis further revealed the vibration patterns of the structure under different frequency excitations, providing profound physical insights into the mechanisms of low-frequency sound insulation. Moreover, by altering the relative angles between the loaded mass blocks could further broaden the effective noise reduction bandwidth which can benefit the understanding on the optimized membrane-acoustic interactions.

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.

Sound insulation performance of membrane-type acoustic metamaterial based on defect state structure

Although conventional Membrane-type Acoustic Metamaterial(MAM) has good sound insulation performance in low frequency bands, the sound insulation performance in middle and high frequency bands is not as good as conventional sound insulation materials with the same quality. This problem still persists by using the double-layer MAM structures. To solve this problem, the defect state is introduced into the double-layer MAM structure. Although the ideal periodic structure is destroyed, the sound insulation performance will also change greatly, and it has a strong creativity. In this paper, the sound insulation performance of MAM with defect states is studied. Firstly, the theoretical model of sound insulation of double-layer membrane-type acoustic metamaterial with eccentric composite mass block (MAMEM) structure is calculated by using modal superposition method and transfer matrix method. Secondly, the influence of different defect locations on the sound insulation of membrane-type acoustic metamaterial with eccentric composite mass block(MAMECM) structure is discussed. The results show that the sound insulation peaks of the angular defect structure appear at 300 Hz, 320 Hz, 1040 Hz and 1410 Hz. The average sound insulation in the whole study frequency band of the angular defect structure is 4.23 dB higher than the non-defect structure. In addition, the experiment verifies the accuracy of the results. Thirdly, based on genetic algorithm, the area enclosed by the sound translation loss (STL) curve of the double-layer MAMECM structure above the mass law curve is taken as the optimization target to optimize the structure topology. The results show that the optimal structure not only has good sound insulation performance in the low frequency band, but also reaches the sound insulation peak at 1230 Hz, 1300 Hz, 1430 Hz and 1450 Hz. Besides, the optimal structure heaviness is reduced by 12%.

Additive manufacturing of membrane-type acoustic metamaterials

Traditional membrane-type acoustic metamaterials have been proven to act as effective lightweight sound insulation materials. However, their geometries cannot be easily incorporated into other acoustic designs in a single workflow. Here, we leverage the enhanced customizability that additive manufacturing provides by introducing 3D printed membrane-type metamaterials that can one day be seamlessly incorporated into a variety of acoustic designs without the need for post-processing. In this study, we present the fabrication workflow to 3D print membranes of varying thicknesses and offer an analysis on print quality. Using a four-microphone normal-incidence impedance tube, we provide preliminary results on the sound transmission loss behavior of these membrane-type metamaterials. Our results show the membranes are fabricated without any significant holes or gaps, and their thicknesses can be reliably controlled.

Numerical study on honeycomb membrane-type acoustic metamaterial with added mass

This paper presents numerical investigations on the transmission loss (TL) of a honeycomb structure with embedded membrane to which small masses are attached. The structure is a lightweight honeycomb membrane-type acoustic metamaterial that presents excellent transmission loss especially at low frequencies. The added mass is a solid material that is attached to the membrane, which is modelled as a linear isotropic elastic material with fixed boundary conditions. The influences of the membrane material properties and of the added mass parameters on the transmission loss are presented. It is demonstrated that the resonant peak amplitude of the transmission loss and its frequency band can be controlled by the properties of the added mass. The various numerical simulation results of configurations with and without added masses as well as various membrane elastic properties are compared. The honeycomb structure used in this study constitutes generally the core layer in sandwich honeycomb panels. While the TL of the honeycomb structure alone is zero, due to the open cell distribution, the integration of a membrane within the honeycomb with added masses induces a significant improvement of the transmission loss. This lightweight metamaterial is shown to attenuate the low frequency noise.

Underwater low-frequency sound absorption performance and broadband absorption design of membrane-type acoustic metamaterials

The underwater low-frequency sound absorption performance of membrane-type acoustic metamaterials (MAM) is investigated in this paper. The MAM unit is composed of a tensioned membrane, an upper cavity frame, a lower cavity frame, a steel backing and a cylindrical mass block located at the geometric center of the membrane. The sound absorption mechanism of MAM and the influence of critical structural parameters are analyzed by numerical simulation. The absorption performance of MAM is further optimized by the parallel combination design of multiple MAM units and the acoustical siphon effect. A design of MAM with 19 units is proposed to improve the absorption bandwidth. The calculation result demonstrates that the structure can effectively absorb sound in the low-frequency range of 250–750 Hz, and the average absorption coefficient is above 0.6. Lastly, the corresponding sample is fabricated, and the underwater sound absorption performance is tested in the standing wave tube. The accuracy of numerical simulation is validated by experiment.

3-D printed membrane-type acoustic metamaterials with tailored performance

While traditional membrane-type acoustic metamaterials act as effective lightweight sound insulation materials, their geometries can neither be easily customized nor incorporated into other acoustic designs in a single workflow. Here, we leverage our established techniques at 3-D printing thin membranes to create custom acoustic metamaterials with tailored performance that can be easily implemented into other acoustic designs without any post-processing. In this study, we present the workflow to additively manufacture flexible membranes with added textural features using low-cost extrusion-based printing methods. Using a custom G-code, we print membranes with controlled mass, stiffness, and porosity while superimposing various surface pattern designs. Using a four-microphone normal-incidence impedance tube setup, we demonstrate the effect of each parameter on the membrane’s sound transmission loss behavior and compare the results against traditional acoustic mass law.

Sound insulation mechanism and prediction of membrane-type acoustic metamaterial with multi-state anti-resonances by weighted-kNN

In this study, we present a swing-arm type membrane-type acoustic metamaterial (MAM) with multi-state anti-resonances. The designed structure is lightweight and can achieve excellent sound insulation in a wide frequency range of 100–1000 Hz. Through the analysis of sound transmission loss and anti-resonance mode, the sound insulation principle of MAM is obtained. Besides, the orthogonal experiment presents the order of the main factors affecting the sound insulation performance. Based on the relative bandwidth as the classification criterion, k-nearest neighbor with analytic hierarchy process and K-Fold cross-validation is utilized to predict different levels of sound insulation.

Optimized membrane-type acoustic metamaterials for alleviating engineering fatigue damage via lightweight optimization

Currently, most acoustic metamaterials have been designed for ultra-thin sizes to achieve perfect and low-frequency sound absorption or insulation performance, with less attention paid to fatigue damage in practical engineering applications. In this study, a lightweight optimal design for the membrane-type acoustic metamaterial is proposed for alleviating fatigue damage. Normally, the elastic membrane was decorated with several metal platelets for tuning the natural frequencies in the membrane-type acoustic metamaterial. However, the sound waves may cause the fatigue damage to the membrane in the long-term engineering applications. The fatigue damage caused by sound can be significantly alleviated by the proposed lightweight optimization for the membrane-type acoustic metamaterial. To maintainthe low-frequency sound absorption performance while achieving the lightweight purpose, a multi-objective particle swarm optimization algorithm is applied to the lightweight optimization of the proposed structure. The fatigue simulation results showed that the corresponding minimum fatigue life is increased by 10.27% using the proposed lightweight approach. Furthermore, the experiments using the dual port measurement without backing were conducted to investigate sound absorption performance of the proposed structure before and after lightweight optimization. Both of theoretical and experimental results showed that the average sound absorption coefficients of the proposed structure after optimization are 41.6% and 22.2% larger than those before optimization, respectively. The total weight of the proposed structure after optimization is 25.9% lighter than that before optimization.

Low frequency sound insulation performance of membrane-type acoustic metamaterial with eccentric mass block

To improve the sound insulation performance in the low frequency band of membrane-type acoustic metamaterial (MAM), membrane-type acoustic metamaterial with eccentric mass block (MAMEM) is used as the object in this paper. The influence of composite mass block on the low frequency sound insulation performance of MAMEM is also studied. Firstly, a mathematical model of sound insulation based on MAMEM was conducted. Secondly, the elastic layer is introduced into the mass block of the MAMEM to form a membrane-type acoustic metamaterial with eccentric composite mass block (MAMECM) structure. The study shows that the peak sound insulation frequency of the structure is obtained with a left shift of 70 Hz, and the introduction of the elastic layer will be beneficial to realize the low frequency regulation of the structural band gap. Thirdly, the influence of the thickness of the elastic and metal layers on the sound insulation of the MAMECM was discussed. The study shows that when the thickness of the metal layer is 1 mm and the thickness of the elastic layer is 10.7 mm, the peak sound insulation reaches 70 dB at this frequency. The peak frequency of sound insulation can reach 260 Hz, which is 140 Hz lower than the MAM at the same mass. Moreover, under the premise that the total mass of composite material blocks remains unchanged, the sound insulation peak frequency of sound transmission loss (STL) curve will shift to the left when the thickness of metal layer is smaller, and the sound insulation at the peak frequency is larger. Finally, the accuracy of the results is verified by experiments.

A study of low frequency sound insulation mechanism of a perforated plate-type acoustic metamaterial

This paper presents a new design of a perforated plate-type acoustic metamaterial (PAM) to evade the influence of membrane pre-tension on the acoustic performance of metamaterials and to enable air ventilation while achieving the designated sound insulation. The study embarks on the analysis of sound insulation mechanism of a typical perforated membrane-type acoustic metamaterial (MAM) from the acoustic context, and discloses that sound transmission loss (STL) peaks of a perforated MAM are due to the strong wave interference between sound sources transmitted through the orifice(s) and the membrane(s). The sound insulation mechanism is explored further in the study by an acoustic impedance analysis of a perforated metamaterial using an electro-acoustic analogy in the latter part of the paper, and the result confirms that the STL peaks of a perforated PAM (or MAM) are indeed the outcome of a strong sound interference. The study also compares an experiment test and a finite element simulation on the sound transmission of a perforated PAM based on the new design. The result confirms that the new perforated PAM can yield a good broadband STL at relatively low frequencies. A practical application using the perforated PAM design is applied to reduce the noise propagation from the compressor compartment of a commercial refrigerator. The test result verifies the effectiveness of the design in terms of both sound reduction and air ventilation.

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).

Bionic design and numerical studies of spider web-inspired membrane-type acoustic metamaterials

Being demonstrated to have excellent soundproof properties, Membrane-type acoustic metamaterials (MAMs) have been extensively investigated. Inspired by a spider web, this study designed a bionic MAM by combining a membrane, frame, and set of resonators. The computational and experimental results show that the bio-inspired model has a 19 % reduction in mass and 61 % expansion in bandwidth. Furthermore, we investigated the laws of three design parameters— membrane shape, resonator position and model size—of the structure soundproof performance and analyzed its multi-state anti-resonance modes. The results show that the round model performed better than other two square models on soundproof performance. The best soundproof performance was achieved when the resonator was positioned at a radius ratio of 0.54. The model still has a substantial noise reduction at reduced size but the risks of failure when size increases. These studies will generate fresh insight into producing more efficient low-frequency sound insulation 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.

Sound insulation performance of double membrane-type acoustic metamaterials combined with a Helmholtz resonator

As one of the representatives of acoustic metamaterials, the membrane-type acoustic metamaterial has excellent sound insulation performance due to its locally resonant features, which makes an extremely broad development prospect in many fields such as aerospace, ship and civil engineering. At the same time, sandwich structures are widely used because of their great mechanical properties. In this paper, we designed a sandwich structure of double membrane-type acoustic metamaterials combined with a Helmholtz resonator, a new structure is presented with both pleasant mechanical nature and admirable acoustic insulation at low frequency. Based on theoretical derivation we calculated the resonant frequencies and out-of-plane displacements of membrane-type acoustic metamaterials. The sound transmission loss, dynamic response and negative characteristics of the new structure are amply analyzed through numerical simulation, and the accuracy of the simulation is verified through experiments. It can be concluded that the average sound insulation performance of this new sandwich structure at 50 Hz–1600 Hz is 30% higher than the single-membrane type sandwich structure. At the same time, the sound insulation performance is improved by 24.8% compared with the double-membrane type sandwich structure which does not increase the cavity height. To sum up, this sound insulation performance of the structure is significantly higher than that of a single membrane-type acoustic metamaterial, with the possibility of flexible changes in cavity height, additional block arrangement form and membrane defect location from multiple angles, and a variety of configurations can be designed according to the actual engineering requirements of both lightweight, load-bearing and sound insulation requirements.

Acoustic Insulation Characteristics and Optimal Design of Membrane-Type Metamaterials Loaded with Asymmetric Mass Blocks.

Membrane-type acoustic metamaterials (MAMs) are the focus of the current research due to their lightweight, small size, and good low-frequency sound insulation performance. However, there exists difficulties for extensive application because of the narrow sound insulation band. In order to achieve broadband sound isolation under the premise of lightweight, a novel MAM with asymmetric rings is firstly proposed in this paper. The sound transmission loss (STL) of this MAM is calculated by an analytical method and is verified by the finite element model. The different properties of the membrane when it is loaded with one, two, or four mass blocks are analyzed. The comparison with the traditional MAM proves the superior performance of this novel MAM. Moreover, by discussing the influence of the eccentricity and distribution position of the masses on the results, the tunability of the sound insulation performance of this MAM is proven. Finally, the Isight platform is used to optimize the MAM to further improve the broadband sound insulation performance: the average STL of the MAM is improved by 15.7%, the bandwidth above 30 dB is improved by 11.5%, and the mass density is reduced by 30.01%.

Controlling the effective surface mass density of membrane-type acoustic metamaterials using dynamic actuators.

Membrane-type acoustic metamaterials (MAM) are thin and lightweight structures that offer exceptional low-frequency sound transmission loss (STL) values, which can exceed the corresponding mass-law significantly. Typically, the high STL of MAM is confined to a narrow frequency band, which is associated with the so-called anti-resonance. This narrow bandwidth reduces the range of potential noise control applications for MAM. To potentially overcome this challenge, this paper presents an investigation into actively controlling the effective surface mass density of MAM by actuating the MAM with a force that is correlated to the acoustic pressure difference acting on the MAM. In particular, it is shown using theoretical and numerical methods that the anti-resonance frequency of MAM can be adjusted over a wide frequency range by passing the incident sound pressure through an adjustable gain. A simple analytical model to predict the frequency shifting, depending on the gain value, is derived. A realization of this concept is further studied, consisting of a circular MAM with a small electrodynamic actuator (to apply a force to the MAM) and a microphone in front of the MAM (to estimate the pressure difference). Finally, experimental results from impedance tube measurements are used to validate the proposed analytical model.

A Preliminary Investigation of an Active Membrane-type Acoustic Metamaterial

One of the most promising features of membrane-type acoustic metamaterials (MAM) is their anti-resonance at low frequencies, which typically exhibits sound transmission loss values that can significantly exceed the corresponding mass-law values. The bandwidth of this anti-resonance, however, is usually very small, which limits the applicability of MAM in practical noise control problems. In previous research it has been shown that different types of actuators (e.g. magnets, electrodes, or pressurized air) can be used to adjust the anti-resonance frequency of MAM, for example to adapt to changing tonal frequencies. However, these actuation principles require additional components to be added to the otherwise lightweight MAM. To overcome these limitations, this paper will present preliminary results from an experimental study of a smart MAM which has the sensors and actuators compactly embedded within the added mass located at the center of the membrane of the unit cell. A small accelerometer is used to measure the vibration of the added mass and this signal is fed back to a controller, which is used to actuate the MAM using a small electrodynamic exciter. An impedance tube is used to measure the sound transmission through the smart MAM and different control algorithms are compared.

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.

Low-frequency sound insulation optimisation design of membrane-type acoustic metamaterials based on Kriging surrogate model

Low frequency is a difficult problem in noise control. How to design new lightweight materials or structures to achieve low-frequency noise reduction is of utmost importance. This study presents a multi-parameter optimisation design procedure for a specific sound insulation frequency and bandwidth of a lightweight acoustic metamaterial. First, a sound insulation model of membrane-type acoustic metamaterials (MAMs) was established based on the finite element method, and the predicted results are validated with results from previous studies. Subsequently, the bandgap characteristics and generation mechanism of the sound insulation peak are analysed. Second, the influences of both material and structural parameters of the membrane and mass block, on the sound insulation characteristics of the MAMs are systematically investigated. They are discussed by first using a single variable control method and then considering the multi-parameter coupling effect. Finally, a Kriging surrogate model for sound insulation prediction of MAMs is established. Aiming at a specific sound insulation frequency and bandwidth, the multi-parameter optimisation design of the MAMs is performed. According to the results, during multi-parameter coupling, the influence law of a single variable on the sound insulation peak of MAMs is unchanged; however, the influence magnitude differs. The Kriging surrogate model can effectively design acoustic metamaterials with a specific sound insulation frequency and bandwidth.