Microperforated Panel Sound Absorber Research Articles

Optimization and Comparative Analysis of micro-perforated panel sound absorbers: A study on structures and performance enhancement

In this study, three MPP (micro-perforated panels) absorber configurations (simple, series, parallel) were investigated via the response surface method (RSM) to broaden the absorption bandwidth. The study focused on the average normal sound absorption coefficient (SAC) in the range of 125–3000 Hz via an impedance tube. The impedance tube results were finally compared with the Finite Element Method (FEM) and Equivalent Circuit Method (ECM) simulations. Samples Fabrication involves 3D printing, with optimized configurations exhibiting expanded absorption bandwidths. The average absorption coefficient was 1.5 times higher in series MPPs and 1.2 times higher in single and parallel MPPs compared to the non-optimal state. In the optimal state, the series and parallel structures outperform the single design, and among the studied factors the hole diameter significantly influenced sound absorption more than others. The alignment of coefficients from various methods with RSM predictions was noteworthy. The results obtained from the FEM and ECM methods align perfectly, This study underscores RSM’s effectiveness, demonstrating optimization benefits and coherence between numerical, theoretical, and experimental models in evaluating MPP absorbers.

The sound absorption properties of a double-leaf micro perforated panel (DL-MPP) made from a double-layered polypropylene material.

Micro-perforated panel sound absorbers are recognized as an alternative method for noise control, offering advantages over conventional porous absorbers. However, the sound absorption of a single micro-perforated panel (MPP) is limited in its ability to cover a broad range of frequencies, especially in the low-frequency region. Therefore, the primary focus of this study is to investigate the sound absorption performance of a double-leaf micro-perforated panel (DL-MPP) absorber, which aims to achieve high sound absorption across a wide frequency range. This study examines the impact of varying parameters, including perforation ratio, diameter of perforated holes, and air gap thickness, on the sound absorption characteristics of a polypropylene-based DL-MPP absorber. Polypropylene was used as the sound absorption material for this investigation. The DL-MPP absorber consists of two perforated panels installed parallel to a rigid back wall, with an air gap between them. To assess the sound absorption performance, a prototype of the DL-MPP absorber was fabricated and tested using a two-microphone impedance tube method following ASTM E1050 standard. The results demonstrate that the optimal sound absorption performance was achieved by designing the MPPs with a 1% perforation ratio, 1 mm diameter of perforated holes, and a 1 mm sample thickness.

Acoustic properties of natural fiber reinforced composite micro-perforated panel designed using 3D printing

The present study investigated the acoustic performance of biodegradable MPP absorbers made of natural fiber-reinforced composites (NFRC) using 3D printing. The novelty of this current research lies in the recent development of a methodology that aids industry professionals in optimizing the production of MPP (Micro Perforated Panel) at a competitive cost. This is achieved by addressing and eliminating issues commonly faced in traditional manufacturing processes, such as manual preparation and pressing. The FDM technique was used to fabricate test samples utilizing the PLA/corkwood composite. Using an impedance tube device with two microphones, the acoustic absorption coefficients of MPPs with different perforation diameters, thicknesses, and perforation rates were measured. Maa's analytical model was used to predict the acoustic absorption performance. Moreover, considering the average sound absorption and total cost of fabricating the samples, RSM-CCD was employed to optimize these samples. In the end, the parallel arrangement of MPP double layer and the combination of MPP with kenaf porous material were tested to improve the sound absorption performance. The results showed that the average sound absorption coefficient of the NFRC-MPP sound absorber is 25% more than that of conventional MPP sound absorbers.

Time-domain extended-reaction microperforated panel sound absorber modeling for acoustics simulation by finite element method

Time-domain extended-reaction microperforated panel sound absorber modeling for acoustics simulation by finite element method

Sound attenuation performance at high sound pressure level of micro-perforated panel sound absorber with embedded resistive screen

In this paper, a composite sound absorber made of a micro-perforated panel (MPP), an air cavity with embedded resistive screen and a rigid back plate is investigated at high sound pressure level (SPL). The sound absorption coefficient predicted theoretically is compared with the experimental measurement at 150 dB and a good agreement is obtained. It is demonstrated that the incorporation of resistive screen within the air cavity improves significantly the sound absorption that presents a large frequency band and remains almost identical with respect to the SPL compared to a classical MPP absorber whose sound absorption peak varies with the SPL. The MPP absorber with the resistive screen glued on the MPP is studied and different resistive screens are compared at 150 dB and it is observed that the sound absorption coefficient increases with a large frequency band, which depends on the airflow resistivity of the screen. A sensitivity analysis shows that the resistance per unit area of the screen affects the acoustic properties of the absorber at low SPL while at high SPL, the acoustic properties are mainly controlled by the perforation ratio of the MPP and the acoustic orifice Mach number.

Acoustic properties of natural fiber reinforced composite micro-perforated panel (NFRC-MPP) made from cork fiber and polylactic acid (PLA) using 3D printing

The present study investigated the acoustic performance of biodegradable MPP absorbers made of natural fiber-reinforced composites (NFRC) using 3D printing. The novelty of this current research lies in the recent development of a methodology that aids industry professionals in optimizing the production of MPP (Micro-Perforated Panel) at a competitive cost. This is achieved by addressing and eliminating various issues commonly faced in traditional manufacturing processes, such as manual preparation and pressing. The FDM technique was used to fabricate test samples utilizing the PLA/corkwood composite. Using an impedance tube device with two microphones, the acoustic absorption coefficients of MPPs with different perforation diameters, thicknesses, and perforation rates were measured. Maa's analytical model was used to predict the acoustic absorption performance. Moreover, considering the average sound absorption and total cost of fabricating the samples, RSM-CCD was employed to optimize these samples. In the end, the parallel arrangement of MPP double layer and the combination of MPP with kenaf porous material were tested in order to improve the sound absorption performance. The results showed that the average sound absorption coefficient of the NFRC-MPP sound absorber is 25 % more than that of conventional MPP sound absorbers. The sample with a perforation diameter of 0.70 mm, a panel thickness of 0.90 mm, and an 8 mm distance between the perforations was selected as the optimal sound absorber. The measurement and model data for NFRC-MPP panels do not correspond well. The parallel arrangement of two layers of MPP and the addition of an optimized kenaf layer behind the MPP significantly improved the sound absorption performance in the intended frequency range. The findings of this study, coupled with data available in the literature for other types of biocomposite Micro-Perforated Panel (MPP), strongly indicate that Cork fiber-based MPP exhibits substantial promise for application, either independently or in conjunction with Kenaf materials, as a material for acoustic conditioning. Implementing smart manufacturing techniques for acoustic panels not only enhances engineering noise control efforts but also amplifies the overall effectiveness of Hearing Conservation Programs.

Sound absorption of acoustic resonant absorbers with rough oblique perforations

Micro-perforated panel sound absorbers are widely used in the field of noise reduction due to their good sound absorption performance. For micro-perforated panel, the acoustic impedance characteristics of the perforation hole play an extremely important role in the sound absorption performance. Here, the acoustic metamaterial in the form of a perforated panel with rough oblique holes is proposed for low-frequency sound absorption. By introducing surface roughness, the acoustic performance of the oblique perforation holes can be adjusted, and the low-frequency sound absorption performance of the perforated panel sound absorber is improved. The theoretical prediction of sound performance has been verified by finite element simulation, and a good consistency has been achieved. The results show that the introduction of surface roughness effectively reduces the resonant frequency and increases the value of sound absorption peak. The introduction of surface roughness and oblique configuration can provide additional acoustic resistance and reactance for impedance matching with air without increasing the thickness of the structure, resulting in more effective low-frequency sound absorption. Physically, the surface roughness causes the periodic concentration effect of the fluid vibration in the hole, which increases the viscosity loss and improves the sound absorption performance of the sound absorber. The theoretical and the numerical models, as well as the low-frequency perfect sound absorption performance (α>0.99) of the proposed metamaterial, are validated by experimental measurements. This work is of great significance to the application of perforated panel absorbers in low-frequency sound absorption.

Series and parallel coupling of 3D printed micro-perforated panels and coiled quarter wavelength tubes

Micro-perforated panel sound absorbers are widely used in noise control applications in the fields of architectural acoustics and transport acoustics. Combining micro-perforated panels with other resonant or sound absorbing systems may broaden the frequency range in which they absorb sound while ensuring that large sound absorption values are reached. In this work, a hybrid sound absorber that combines a micro-perforated panel and a coiled quarter wavelength tube is proposed. Series and parallel configurations of these two systems are studied from analytical, numerical, and experimental point of views. A comparison of two three-dimensional (3D) printing techniques for the production of samples highlights the main challenges for the practical implementation of the proposed design. The advantages and limitations of series and parallel arrangements are discussed and while the parallel configuration is more complex to setup in practice, it provides an improved sound-absorbing performance compared with the series configuration. Finally, the reproducibility of the hybrid absorber in parallel configuration is confirmed by testing samples that were produced with two different 3D printers and in two different laboratories.

Optimum Design of Multi-layered Micro-perforated Panel Sound Absorbers in Combination with Porous Materials in an Arbitrary Frequency Range

Optimum design of sound absorbers with optimum thickness and maximum sound absorption has always been an important issue to noise control. The purpose of this paper is an achievement of optimum design for micro-perforated panel (MPP) and its combination with a porous material and air gap to obtain maximum sound absorption with maximum overall thickness up to about 10 cm in the frequency range of (20-500 Hz), (500-2000 Hz) and (2000-10000 Hz). For this purpose, the genetic algorithm is proposed as an effective technique to solve the optimization problem. By using the precise theoretical models (i.e. simplified Allard's model and Atalla et al.’s model) to calculate the acoustic characteristics of each layer consisting of MPP, porous material, and airgap, we obtained more precise optimized structures. The transfer matrix method has been used to investigate the sound absorption of structures. To verify the operation of the programmed genetic algorithm, the results obtained from the optimization of the MPP absorber are compared with others that show the accuracy and efficiency of this method. After ensuring the accuracy of the proposed programmed genetic algorithm with more precise theoretical models to achieve the characteristics of each layer, new structures were obtained that have a much better sound absorption coefficient in the desired frequency range than the previous structures. The results show that the sound absorption coefficient can be reached to 0.67, 0.96, and 0.96 in the mentioned first, second, and third frequency range, respectively by optimum design parameter choosing of a composite structure.

Optimization of micro-perforated sound absorber using Particle Swarm Optimization (PSO)

This study investigates the acoustic properties of micro-perforated panel (MPP) as an alternative to passive noise control. In order to obtain high sound absorption over broad frequency band, the analysis of sound absorption performance of MPP sound absorber should be conducted based on 3 major design parameters, such as perforation diameter, d, air cavity depth, D, and distance between perforations, b, of MPP. Next, the optimization of sound absorption coefficient for MPP sound absorber need to be done by using the Particle Swarm Optimization (PSO) algorithm and the optimum parameters of a single layer MPP sound absorber should be obtained for achieving higher sound absorption which the sound absorption coefficient, α + 0.5 with a wider frequency band. The PSO is used in order to optimize the panel construction to provide maximum sound absorption coefficient in a determined wide band frequency range. Experiments are carried out at normal sound incidence and plane waves. A good agreement is achieved between the theory and the experiments.

Implementation experiment of a honeycomb-backed MPP sound absorber in a meeting room

This paper presents the absorption performance of honeycomb-backed microperforated panel (MPP) absorbers, which are needed to improve the acoustics of an existing 91 m3 small meeting room where the reverberation time is over two seconds from 250 Hz to 2 kHz, for comfortable speech communication. In Japan, MPPs are difficult to use combustible materials, particularly, panels with holes for interior walls owing to fire regulations. Therefore, we implemented the MPP absorber as an additional attachment that can be hung on walls and ceilings. First, the absorption characteristics of the MPP absorber were designed to reduce reverberation times at mid-frequency using an electroacoustical equivalent theory. Then, a wave-based finite element method simulation was used to determine the absorber placement. Absorption coefficients of the honeycomb-backed MPP absorber were also measured in an irregularly shaped reverberation chamber. Finally, the effect of the installed MPP absorbers was checked by acoustic parameter measurements. As a result, we observed that the reverberation time was reduced under 1.5 s in all frequencies, the equivalent absorption area doubled, the early decay time values were also reduced from 2.7 s to 1.0 s at 1 kHz, the clarity (C50,mid) increased by more than 5 dB, and the speech transmission index (STI) value increased from 0.55 to 0.67 by one rank up.

A wideband triple-layer microperforated panel sound absorber

Microperforated panels are light, clean and tunable sound absorbers, which fundamentals were already established in the previous century. They consist of a distribution of minute holes of diameter d on a panel of thickness t with perforation ratio ϕ in front of an air layer of thickness D. Therefore, the frequency band of absorption of a single-layer microperforated panel depends on (d, t, ϕ, D). In noise control applications, such a simple structure provides absorption in the frequency range of interest if holes are of sub-millimetric diameter. The former single-layer microperforated panels had two main weaknesses: narrow frequency band of absorption and a high manufacturing cost. However, nowadays these deficiencies can be easily surpassed. The absorption frequency band can be drastically increased by means of multiple-layer structures. The manufacturing cost may be reduced with the application of techniques currently used in the advanced circuitry industry. This is illustrated by the design of a triple-layer microperforated panel yielding absorption in almost four and a half octaves. The parameters of the triple-layer microperforated panel are optimised by Simulated Annealing to provide maximum absorption within a prescribed frequency band.

Simplified Method of Simulating Double-Layer Micro-Perforated Panel Structure

The micro-perforated panel (MPP) structure has been widely used in various noise control applications, and thus its acoustic performance prediction has been receiving increasing attention. The acoustic performance of simple MPP structures, such as a MPP sound absorber, has been predicted using an analytical calculation method. However, this is not a suitable approach toward predicting the acoustic performance of complicated MPP structures, owing to the structural complexity of these structures. Moreover, the many perforations of submillimeter scale diameter render the MPP structures very difficult to analyze using numerical simulation. Thus, this study focused on two different simplified MPP simulation methods: the transfer admittance method and the equivalent fluid method, and their application on double-layer MPP structures. Based on the two simplified MPP simulation methods, the transmission loss value of the double-layer MPP mufflers with two sets of different structural parameters was calculated, respectively. The predicted results were compared with the impedance tube measurements. The results revealed that the two simplified MPP simulation methods could effectively predict the acoustic performance of double-layer MPP structures. Moreover, the prediction based on the transfer admittance method can outperform the two simplified simulation methods.

Bayesian model selection for multilayer microperforated panel sound absorber design

Microperforated panel (MPP) sound absorbers are capable of providing high sound absorption coefficients without the use of fibrous materials; however, they typically function in narrow frequency ranges. By combining multiple MPPs into a multilayer absorber, the frequency bandwidth may be increased while maintaining a high absorption coefficient. Modeling the acoustic properties of an MPP absorber requires four physical parameters per MPP layer. Since each additional MPP layer in a multilayer absorber increases the complexity of the acoustic model, Bayesian model selection is well-suited to the task of designing a multilayer MPP absorber. In such a design, minimizing the number of layers used while still satisfying the design goals is desirable, in order to optimize material usage, cost, and space required by the absorber. In a full Bayesian design framework, model selection determines the number of MPP layers required, while parameter estimation determines the (physical) design parameters for each layer. In this work, an example design scheme is specified to satisfy a practical need for acoustic absorption. The Bayesian framework produces a three-layer MPP design which meets the target requirements. This absorber design is constructed, and impedance tube measurements are obtained to validate the acoustic absorption properties.

Acoustic measurement of a 3D printed micro-perforated panel combined with a porous material

The sound absorption coefficient of a micro-perforated panel (MPP) backed by a porous sound absorbing material is investigated in this paper. The feasibility to fabricate an MPP acoustic absorber using 3D printing technology is presented. The test specimens are made of polymer material, and they are printed with different perforation ratios. A porous sound absorbing material is added to the MPP samples to form an acoustic absorber structure. Their sound absorption coefficient is experimentally measured by using the impedance tube method. The results obtained are theoretically validated by using the transfer matrix method (TMM). The MPP is modelled using Maa's method, and the equivalent fluid model is used to calculate the acoustic property of the porous sound absorbing material layer. The results show that the sound absorption coefficient of a 3D printed MPP backed by a porous sound absorbing material agrees fairly well with the theoretical model. By adjusting the perforation ratio, MPP acoustic absorbers with high absorption peaks can be implemented. The results in this paper provide a new approach for fabricating MPP sound absorbers for acoustic applications.

Study on inhomogeneous perforation thick micro-perforated panel sound absorbers

Study on inhomogeneous perforation thick micro-perforated panel sound absorbers

Numerical study on the absorption performance of MPP sound absorber installed in small rectangular rooms

Sound absorbers using microperforated panel (MPP) are one of the most promising alternatives of the next-generation sound absorbing materials, thanks to the superior material performances in durability, weatherability, recyclability, and flexibility of design, as well as the attractive broadband sound absorption characteristics. Many previous researches focus on the development of absorbers itself. However, in order to bring out the absorption performance sufficiently or to use it appropriately in room acoustics applications, it is important to understand the absorption effect of MPP absorbers on sound fields in rooms. For the purpose, recently, highly accurate wave-based acoustics simulation techniques such as FEM can be used to analyze sound fields in practical sized rooms with MPP absorbers. This paper presents the absorption performance of MPP absorbers installed in a small rectangular room of 91 m3 using 3D-FEM in frequency domain. Both the steady-state and the unsteady-state sound fields are calculated up to 1 kHz under the various absorber locations. The unsteady-state sound fields are calculated using inverse Fourier transform of transfer functions of rooms. The results are compared to explore the optimum sound absorber locations.

Experimental study on sound absorption performance of microperforated panel with membrane cell

Abstract Microperforated panel (MPP) absorbers have been widely used in noise reduction and are regarded as a promising alternative to the traditional porous materials. However, the absorption bandwidth of a single-layer MPP is insufficient to compete with the porous materials. In order to improve the sound absorption ability of the single-layer MPP, a composite MPP sound absorber with membrane cells (MPPM) is introduced. Sound absorption properties of the MPPM are studied by the impedance tube experiment. Results show that the membranes have a significant influence on the sound impedance. The sound absorption performance of MPPM gradually increases with the increase of the membrane area. The single-layer MPP with some small area membrane cells may have the same effect and single large area membranes. By adjusting the size of the membrane cells, one can implement a sound absorber with a wider absorption bandwidth and higher absorption peaks than the single-layer MPP.

A Compound Micro-perforated Panel Sound Absorber with Partitioned Cavities of Different Depths

The micro-perforated panel (MPP) sound absorber is becoming a good replacement of conventional porous absorbers in building noise control. The MPP absorber is fiber-free and avoids potential harms such as powdered fibers and damage to the person's health. This paper presents a new compound MPP sound absorber architecture with excellent sound absorption performance both on higher sound absorption coefficient and broader absorption band compared with single MPP absorber. The absorber consists of an array of parallel-arranged MPP sub-absorbers with different depths, where different local resonances are apparent and dominate. In this paper, firstly, an analytical method is proposed to look into the mechanism of the absorber architecture design and this method is validated through simulations based on a finite element procedure. Secondly, the acoustic properties from different MPP absorber dimension sets are investigated through simulations with the proposed theoretical method. Results show that the presented MPP absorber can have normal incidence sound absorption coefficients higher than 0.5 over the frequencies from 370Hz to 2520Hz, with maximum value of 0.9. This indicates that the proposed MPP absorber provides a good alternative for indoor sound absorption applications in commercial and industrial buildings.

Optimization of double-layered micro-perforated panels with vibro-acoustic effect

A vibro-acoustic effect, in which the classical plate equation is coupled to the acoustic wave equation, was utilised to optimally tune a double-layered flexible micro-perforated panel (MPP), to achieve higher sound absorption coefficient and wider frequency band. The first nine modes considered in the present modelling study were obtained by using the finite element analysis. Results of the vibro-acoustic model, applied to a single layer MPP, were found to be in a good agreement with other published results; thus, the model was used to develop the equivalent electro-acoustical circuit of a double-layered MPP sound absorber. The simulated annealing optimization technique was used to obtain the optimal design parameters of the MPP sound absorber that were needed to achieve the maximal averaged sound absorption coefficient for the frequency band 200–1,000 Hz. The optimized double-layered MPP sound absorber improved the sound absorption coefficient by 8.88–12.52 % compared with the model without the vibro-acoustic effect. Mode (1, 1) was found to dominate the sound absorption performance compared to the other nine mode shapes that were considered in the present study. The effects of configuration, thickness, damping ratio, and boundary condition of the MPP on the sound absorption coefficient were also investigated.