Micro-perforated Plate Research Articles

Vibration behavior of a microperforated plate within an acoustic nonlinear framework

Microperforated plates (MPP) can add substantial damping in the low-frequency range. MPP are known to dissipate energy through thermo-viscous interactions between shearing adjacent fluid layers near the perforation solid walls. Under linear operating conditions, a previous work carried out by the authors showed that the added damping reaches a maximum at a characteristic frequency which solely depends on the perforation parameters. However, MPP is also suitable in environments subject to high levels of mechanical excitation and, consequently, high fluid velocity within the perforations. Two types of nonlinearities should then be considered: (1) an acoustic nonlinearity induced by high fluid velocity, and (2) a nonlinearity induced by large structural displacements. This work only explores the former. The acoustic nonlinearity is modelled by the Forchheimer resistivity correction, a function of the fluid-solid relative velocity in the perforations, introduced into the equations subsequently solved numerically. Experimental measurements using a laser vibrometer on a perforated cantilever beam validate the proposed model. Results show that, under high excitation levels and at the characteristic frequency, the maximum added damping can reach a maximum, depending on the MPP parameters, at a critical value of the relative fluid-solid velocity.

Acoustic radiation of a fluid-saturated microperforated plate

It is known that fluid-saturated microperforated plates (MPP) dissipate energy and are substantially damped through thermoviscous dissipation taking place in the thermoviscous skin on the solid wall of the perforations. The aim of this work is to explore the acoustic radiation of a microperforated periodic cell to investigate the intercellular coupling and the complexity of near-field radiation, and to derive a criterion related to the near-field far-field transition. A numerical modeling using the finite element method is developed to solve the elastic and thermo-visco-acoustic (TVA) multiphysics problem. The TVA calculates explicitly the thermoviscous losses on the acoustic wave in the periodic cell studied. Numerical results show that the distance of the near-far field transition is significant at low frequencies, passing through a minimum for a frequency depending on perforation parameters (diameter and ratio) before increasing again as a frequency function. The radiated acoustic power and radiation efficiency are compared with those derived from the theoretical MPP vibration model. It is found that the microperforations and resulting added damping, around a characteristic frequency, reduce the acoustic radiation efficiency of the MPP compared to the corresponding non-perforated plate.

Sound absorption performance of a micro-perforated plate sandwich structure based on selective laser melting

ABSTRACT This study proposes a sandwich structure of triply periodic minimal surface (TPMS) based on the theory of micro-perforated plates. This structure was processed using laser selective melting (SLM) with the acoustic-vibration theoretical model established through the acoustic-electrical analogy method. The theoretical model was verified by comparison with the experimental results, showing that the micro-perforated plate TPMS sandwich structure exhibited good sound absorption performance with the maximum sound absorption coefficients being higher than 0.8. The micro-perforated plate TPMS sandwich resonated when excited by sound waves. The change in the volume fraction affected the size of the cavity volume behind the micro-perforated plate, thereby affecting the resonance frequency. The increase in volume fraction decreased the volume of the cavity behind the structural plate, the sound absorption performance to increase, the resonance frequency to move towards high frequencies, and the sound absorption bandwidth to decrease. The resonance frequency was negatively correlated with the panel thickness. The increase in the panel thickness increased the maximum sound absorption coefficient and decreased the sound absorption bandwidth when the structure resonated. Also, high-order resonance frequencies appeared when the number of cell layers increased to a certain level.

Sound absorption performance of double layer sandwich structure containing micro-perforations and extended necks

In this study, a double layer sandwich panels made of micro-perforated plate and perforated plate with extended necks is proposed and its acoustic attenuation is studied using the finite element method. The top panel of the structure is micro-perforated and is connected to a first honeycomb structure cells. The internal panel is perforated, and a neck is connected to each perforation and extends into each cell cavity of the second honeycomb structure. The proposed material design is made of 33 micro-perforations and 33 extended necks and has excellent mechanical stiffness due to the honeycomb structure performance. This study shows how to design the parameters of the necks and the micro-perforations to widen the sound absorption frequency band. With identical micro-perforation diameters and identical necks, the sound absorption coefficient presents two resonance peaks where the surface impedance is close to the impedance of air. The number of the sound absorption peaks increases when different micro-perforation diameters and different necks are used while the sound absorption of conventional double layer sandwich structure is zero over the entire frequency range. The proposed material design can be used to attenuate the noise in various engineering fields that require good bending stiffness.

An energy method for predicting and suppressing the instability of a three-dimensional thermoacoustic coupling system with a micro-perforated plate

An energy method for predicting and suppressing the instability of a three-dimensional thermoacoustic coupling system with a micro-perforated plate

Performance of Sound Absorption and Noise Reduction for Dislocation Honeycomb Sandwich Panel With Built-in Coating

The effects of diatom mud coating on characteristic impedance is studied by using the double-thickness method. The parallel relationships among the concave arc column filled with diatom mud, honeycomb cells, the overall core layer, and micro-perforation are considered in using the acousto-electric analogy method. In the case of a series relationship of plates, the sound absorption coefficient of the honeycomb structure of the micro-perforated plate is calculated. The effects of diatom mud coating and dislocation arrangement on the sound absorption coefficient of sandwich panels are numerically simulated by COMSOL. To further verify the reliability of the sound absorption theoretical model, test specimens are made and the effects of dislocation arrangement and diatom mud coating on sound absorption performance are tested by using impedance tube equipment. The effect of dislocation arrangement and diatom mud coating on the sound absorption performance of low-frequency noise of sandwich panels is analysed from the parameters of sound absorption coefficient, resonance frequency, acoustic impedance, and fitting results.

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.

Design a special micro-perforated plate coupled with the labyrinth metamaterial with improved sound absorption properties at medium and low frequencies

The micro-perforated panel structure has good sound absorption performance in medium and high frequencies, and the labyrinth metamaterial structure has good low-frequency sound absorption performance. Both the two structures are relatively simple, and can be obtained by simple processing with resin material, which is convenient for batch production. In order to enhance sound absorption ability for the sound absorption structure within low frequency, this research work has put forward one coupled structure via the micro-perforated panel and three second-order maze metamaterials structure, resulting in a coupled structure with a low-frequency sound absorption performance. Combination of equivalent circuit method calculates acoustic resistance and absorption coefficient for the sound absorption structure, and genetic algorithm has been employed to optimize the parameters of this sound absorption structure. Finally, the theoretical calculations analysis results have been verified by finite element simulation, which shows the trend of the curve of sound absorption coefficient of the two structures was basically consistent. And the sound absorption coefficient of the three peaks is all above 0.7, and the mean value of the sound absorption coefficient is above 0.6 at the acoustic frequency of 0–1500[Formula: see text]Hz, indicating that the coupled structure has a good performance of absorbing medium- and low-frequency sound waves.

A composite acoustic black hole for ultra-low-frequency and ultra-broad-band sound wave control

Achieving ultra-low and ultra-broad-band sound absorption and full-band sound insulation is a major challenge. Here, we propose a composite structure of a multilayer micro-perforated plate and acoustic black holes to achieve this purpose. Combining the stable sound absorption effect of the multilayer micro-perforated plate in the full frequency band and the sound insulation effect of the acoustic black hole in the low frequency and the excellent sound absorption effect in the high frequency, the excellent sound control effect of 600–3150 Hz absorption coefficient greater than 0.8 and 100–3150 Hz sound transmission loss greater than 50 dB is achieved. The acoustic properties of different components and different acoustic black hole outlet were evaluated by finite element method, and the principles of sound absorption and insulation of the composite structure were elaborated. Finally, the results of finite element method are verified by impedance tube experiments. This work can make further progress in elucidating the acoustic properties of the ABH and open up new avenues in the control of ultra-low and ultra-wide frequency acoustic waves.

Broaden the sound absorption band by using micro-perforated plate back cavities with different cross-sectional areas

In finite size micro-perforated plate structure, the cross-sectional area size of back cavity will affect the resonant frequency of structure. Based on transfer matrix and the characteristics of acoustic propagation in variable cross-section channel, the sound absorption characteristics of the double-layer micro-perforated plate structure with variable cross-section back cavity are studied and analyzed, and a theoretical analysis model of the variable cross-section back cavity micro-perforated plate structure is established. By comparing the theoretical model with the finite element model, the effect of abrupt changes in the cross-sectional area of the back cavity on the noise reduction performance is obtained. As for the double-layer micro-perforated plate in this paper, the bigger the cross-sectional area of back cavity of inner micro-perforated plate, the lower the frequency of first peak absorption coefficient of structure will be and the higher the frequency corresponding to second absorption coefficient peak of structure. Utilizing this feature, a combined micro-perforated plate structure is designed, which has back cavities with different inner cross-sectional areas, and ultimately broadening the structural sound absorption band. Additionally, through using 3D printing technology to produce samples and conducting experimental tests in the impedance tube. Experiments show that the structure can achieve an absorption coefficient of more than 0.8 within the frequency range of 500–1650 Hz, which further improving the noise reduction performance of the MPP structure. The feasibility of variable-sectional back cavity structure for the design of low-frequency and broadband noise reduction absorber is verified.

Acoustic metamaterial composed of zigzag channel and micro-perforated plate for enhanced low-frequency sound absorption

We propose the theoretical design and experimental authentication of an ultrathin sound absorber consisting of a perforated plate and a back cavity with zigzag channels for realizing high-efficiency and broadband absorption of low-frequency sound. The dependence of the absorption performance on the structural parameters is analyzed, which suggests the possibility of decreasing the peak frequency of resonance noise absorption with equal compactness of device. Based on this, we propose a hybrid design composed of multiple structures with different parameters to effectively expand the working bandwidth, and propose to further optimize the low-frequency absorption performance by adjusting the inclined partitions in the zigzag channel. The experimental results show that nearly 100% sound absorption is obtained at the resonance frequency (< 500 Hz) with an absorber 30 times thinner than the wavelength. We envision our designed sound absorber with deep-subwavelength size, broadband functionality, and easy fabrication to find wide applications in noise control engineering.

Sound absorbing properties of spiral metasurfaces inspired by micro-perforated plates

As a kind of classical low-frequency sound-absorbing material, the microperforated plate (MPP) has been widely used. Here, we inspired by the sound absorption mechanism of the MPP, a spiral metasurface (SM) is designed and the analytical solution of acoustic impedance and sound absorption coefficient are obtained. The relationship between the sound absorption properties of the MPP and the SM with their own structures is systematically studied, and the analytical solutions are used to optimise the structure. It is concluded that the MPP and the SM of the same thickness achieve effective absorption in the frequency range between 390-900 Hz and 1920-4266 Hz, with a total thickness less than 1/6 of the wavelength. Meanwhile, the numerical calculation shows that the MPP and SM can match well with the background medium in the effective rang. Our study provides new insights into the design methods of sound-absorbing materials and is potentially suitable for many acoustic engineering applications.

Acoustic transmission characteristics based on coiled-up space metamaterials

Coiled-up metamaterials with solid plate (SC) and with micro-perforated plate (MPC) are proposed for broadband low-frequency acoustic insulation and absorption. Firstly, the sound transmission theory of the double-layer plate and the impendence of the micro-perforated plate coupled with the coiled-up channel are introduced to obtain the dependence of structural parameters on the acoustic characteristics. Then, the acoustic performances of SC and MPC are investigated numerically and verified by experiments, and the effects of geometry parameters are analysed to predict the acoustic performance of SC and MPC. The minimum sound transmission loss (STL) of SC with a thickness of less than 2 cm is higher than 20 dB and the average STL reaches 45 dB at [0, 1600] Hz. The multi-order resonances of coiled-up space induce STL valleys but provide 10 dB improvement at valleys compared with double-layer plates. The MPC achieves narrow absorption at 422 Hz and 1232 Hz, which are induced by the resonances of coiled-up channels and 99.99 % of total energy dissipation is viscous dissipation mainly occurring in MPP. Coiled-up space with embedded porous materials (PTM) achieves above 0.9 absorption coefficient at [700, 1600] Hz. The optimized MPTMs, which consists of three parallel MPCs guided by the genetic algorithm (GA) and a single PTM unit, can reach a normal incident average absorption coefficient of 0.80 at [342–2000] Hz and a random incident absorption coefficient above 0.5 at [352–1862] Hz.

Theoretical and experimental study on sound absorption performance of Al2O3-polyurethane foam and microperforated plate composite structure

Low-frequency noise pollution in substations has a significant impact on the physical and mental health of workers. Reduction low-frequency noise pollution is an urgent problem to solve for researchers. In this paper, the different structures of Al2O3-polyurethane composites and micro-perforated plate were constructed, and the effects of cavity depth, perforated plate, and foam position on sound absorption properties were comprehensively investigated. The results showed that the position of perforated plate and the arrangement of resonance structure were the two most important factors affecting sound absorption performance. When the sound wave passed through the plexiglass plate–cavity–composites foam–perforated plate in turn, the peak position of sound absorption coefficient was located in the ultra-low frequency range. Meantime, the simulation study showed that the friction between the air column and the cavity wall in the perforated plate can consume sound energy to achieve sound absorption.

Investigation on the sound absorption of cross-stitched fabric by airflow resistance and sound-induced vibration effects

The main aim of this work is to investigate the acoustical properties of cross-stitched fabric, which exhibits a similar structure with micro-perforated plate. The sound absorption coefficients of cross-stitched fabric with different specifications were measured, where the backing air cavity distance is 1 cm, 2 cm, and 3 cm, respectively. These distances are suitable to the practical interior decoration applications of cross-stitched fabric painting. Cross-stitched fabric can be made into diversity of artistic patterns through manual or mechanized embroidery technology. This work has also studied the effects of multifarious embroidered patterns on the sound absorption coefficients of fabrics with different backing air cavity distance. Classical micro-perforated model, vibrational micro-perforated model, and airflow resistance based model were used to predict the sound absorption of cross-stitched fabric. In summary, cross-stitched fabric with exquisite patterns is expected to be a promising sound absorber for potential room acoustics applications.

A study on ultra-thin and ultra-broadband acoustic performance of micro-perforated plate coupled with coiled-up space structure

The sound wave of low-frequency noise has strong penetration, consumes less energy in the propagation process, and is not easy to be consumed by traditional materials. In order to solve this problem, the micro-perforated plate (MPP) coupling a coiled-up space structure (MPCS) has been proposed. The MPCS is composed of an MPP and a coiled-up space structure, and its overall thickness is only 30 mm. The finite element method (FEM) and theoretical calculation were used to predict the sound absorption performance of a single MPCS. Results show that this structure is 100 % effective at absorbing sound at the resonance frequency. Moreover, the effects of the perforation ratio, aperture, and cavity length L of the MPCS have been studied in this paper. We constructed a sound-absorbing unit (MPCSs) consisting of three coiled-up space channels and six micro-perforated plates, then a broadband sound absorbing body (Bi-MPCSs) was constructed, which has two absorbing units with different parameters in parallel. Its sound absorption achievable reached more than 50 % in the range of 415 Hz–905 Hz, and the average sound absorption was more than 75.6 %. Next, the theoretical calculation results verify the accuracy of the simulation results. To further broaden the sound absorption performance of Bi-MPCS, a low-frequency and ultra-wide frequency sound absorption body (F-MPCSs) composed of four different parameters absorbing units (MPCSs) were constructed. Interestingly, the sound absorption of the absorber achieved more than 50 % in the range of 350 Hz–1150 Hz, and an average sound absorption reached 66.7 %.

A pre-screening study of honeycomb sandwich structure filled with green materials for noise reduction

To maximize the potential of the lightweight and high structural performance of composite and to integrate noise reduction function at the same time, the paper reports a noise reduction composite based on honeycomb sandwich structure by filling the honeycomb with different plant and synthetic fibers and utilizing micro-perforated plate (MPP) as the face sheet. The sound-absorbing effect of these structural samples was characterized and compared. The porosity and density of the filler material and the fiber cloth configuration were calculated and measured. The results show that the filling in the honeycomb significantly increases the sound absorption coefficient and widens the sound absorption band. Meanwhile, the MPP parameter determines the peak frequency of the sound absorption curve. Especially in the range of 125 Hz-4000 Hz, cotton and polyester filling provide the highest average sound absorption coefficients of 0.532 and 0.483 among the five materials pre-studied, while the absorption coefficient of the unfilled sample is about 0.15. The results reveal that a filled honeycomb structure with an MPP face sheet can reduce noise while maintaining mechanical properties. The noise-reduction function-integrated structures can potentially influence construction, transportation, and infrastructure as lightweight and space-saving solutions.

Realizing the perfect sound absorption and broadening effective band using porous material and micro-perforated plate

The noise attenuation ability of a single material or structure, especially for low-frequency noise, is limited by its thickness. Aiming to achieve high-efficiency noise attenuation at low frequencies, this paper proposes the methods of porous material filling and micro-perforated plate (MPP) embedding to design a perfect sound absorber at different frequencies using the under-loss Helmholtz resonator (HR). Based on the transfer matrix method, the theoretical calculation models of the sound absorption coefficients of the HR, Helmholtz resonator with porous material (HRP), and Helmholtz resonator with micro-perforated plates (HRM) are constructed. Based on the theoretical models, the under-loss absorber HR1 with the peak absorption at 243 Hz, and the HRP and HRM with perfect absorption at 212 Hz and 157 Hz are designed, respectively. The impedance analysis and complex frequency plane method are used to analyze the sound absorption mechanisms of the HR1, HRP, and HRM. The accuracy of the theoretical model is verified by the finite element method. Finally, the three acoustic absorbers are manufactured using 3D printing technology, and the absorption coefficients are evaluated experimentally. The experimental results show that the HR1 has a high working frequency at 245 Hz and a narrow bandwidth of high-efficiency sound absorption ([Formula: see text]), which is only 12 Hz. The working frequency of the HRP is 214 Hz, and its high-efficiency sound absorption bandwidth is 54 Hz. The HRP has the lowest working frequency at 157 Hz and the widest high-efficiency sound absorption bandwidth of 58 Hz among the three absorbers. The research results presented in this paper provide a reference for the realization of low-frequency broadband noise attenuation designs and have certain application potential in noise control.

Enhancing sound absorption for an acoustic metastructure with extended tubes at ultra-low frequency

A micro-perforated plate (MPP) as a typical acoustic absorber has ideal sound absorption performance at mid-frequency. A novel metastructure with a MPP and multiple sub-cavities (MPP-MSC) is proposed to broaden the sound absorption frequency range based on Helmholtz resonance, and its sound absorption performance is studied theoretically, numerically, and experimentally. Then, the genetic algorithm is adopted to extend the effective sound absorption band by 120 Hz and reduce the structure thickness to less than 61 mm, which is about 40% thinner than the existing structures. Additionally, a perforated plate with extended tubes (PPET) and porous sound absorptive material (PSAM) are introduced into the metastructure to enhance sound absorption performance in the ultra-low and mid-frequency range. Therefore, the composite sound absorber (PP-MPP-MSC) composed of PPET, PSAM, and MPP with superior sound absorption performance is proposed. Specifically, the effective acoustic absorption frequency of the structure can be broadened to 200–1800 Hz with a maximum thickness of 61 mm. It is worth noting that the design and fabrication of PP-MPP-MSC are relatively accessible, and effective sound absorption performance can be achieved in a certain frequency range, which presents the guiding role for current noise reduction applications.

Vibration and damping analysis of a thin finite-size microperforated plate

Microperforated plates (MPP) are commonly used to absorb acoustic waves in sound control technologies. However, less is known concerning the added damping exhibited by thin finite-size MPPs. This added damping effect is known to be induced by viscous and thermal exchanges in the boundary layers near the fluid–solid interface of the perforations, which results in energy dissipation. The present work actually shows that MPPs can feature a significant added viscous damping, especially at low frequencies of vibration. An analytical approach based on an alternative form of the Biot theory for finite-size porous plates is developed. Parametric studies highlight the existence of a characteristic damping frequency at which the added damping of the perforations reaches a maximum. For specified boundary conditions, the damping level can be maximized by adjusting the geometrical parameters of the perforations (diameter, perforation ratio) so that the resonance frequency of the plate coincides with the characteristic damping frequency. The damping reaches a maximum at a particular frequency, and is also effective over a non-negligible bandwidth. Formulations on the mass density and Young’s modulus as a function of the perforation ratio are provided to address the sensitivity of mass and stiffness to the microperforations. The structural damping capabilities of MPPs are validated by measurements on finite-size MPPs which confirm the significant damping increase in the low-frequency range.