Double-panel Partition Research Articles

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

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

A metaporoelastic structure that overcomes the sound insulation weaknesses of single and double panel partitions

Single and double panel partitions are well known for their sound transmission loss weaknesses in the vicinity of their structural resonances: the first mode of the finite size panel and the mass-spring-mass resonance of the double panel. In this paper, we investigate the use of a poroelastic based metamaterial to address this problem. The metamaterial is a network of poroelastic beams, the first bending mode of which is tuned at the targeted panel resonance. The porous nature of the resonators allows taking advantage of its dissipative properties stemming from the interaction between solid and fluid phases. For the double panel application, where a porous layer is generally present, the effectiveness of the poroelastic metamaterial relies on the design of its shape and mounting conditions. First, the sound transmission loss of a finite size single panel is studied experimentally in a rectangular duct under normal incidence. It is shown that the poroelastic metamaterial increases the transmission loss up to 12 dB at the first mode of the panel. Using resonators tuned at different frequencies makes it possible to spread this gain. The attenuation mechanisms are analyzed by simulation using a finite element model. Secondly, the double panel partition is investigated with a periodic finite element model using the Floquet-Bloch theorem. Finally, the impact of several parameters like airflow resistivity and filling fraction on the efficiency of the metaporoelastic structure is illustrated considering a diffuse field excitation.

Enhancing the sound transmission loss in double-leaf partitions with lateral local resonators substructure

We report theoretically on the sound transmission loss performance through a periodic double plate acoustic metamaterial made of lateral local resonance (LLR) substructure. The unit cell of the substructure consists of a four link mechanism, two lateral resonators, and a vertical spring. The combination of space harmonic expansion and Bloch-Floquet theorem are used to analyze this present study. Computed results show that high sound transmission loss (STL) up to 60 dB at 62 Hz is reached with the metamaterial plate while the mass spring mass resonant is observed for the conventional periodic double plate at the same frequency. The introduction of a negative stiffness spring causes an increased STL at low frequency. The potential of lateral resonant metamaterials to improve the sound transmission loss (STL) in the frequency region around the mass-spring-mass resonance for periodic double panel partitions is demonstrated.

Analysis of Vibration and Acoustic Characteristics of a Simply Supported Double-Panel Partition under Thermal Environment

Numerical studies on the vibration and acoustic characteristics of a simply supported double-panel partition under the thermal environment are presented by the modal superposition approach and temperature field theory. Many factors are considered in this theoretical research, including acoustic refraction, dynamic response of the panel under thermal and acoustic load, vibroacoustic coupling characteristic analysis, and the variation of material properties. To access the accuracy and feasibility of the theoretical model, a finite element method is proposed to calculate the natural frequencies and mode shapes. The results show that the vibration and acoustic responses change obviously with the change of thermal stress and material properties. The rise of the graded thermal environment and thermal load decreases the natural frequencies and moves response peaks to the low-frequency range. The first valley of sound transmission loss is well consistent with the mode frequency. Finally, the relation between the average sound insulation and the thickness ratio is analyzed.

Metamaterial foam core sandwich panel designed to attenuate the mass-spring-mass resonance sound transmission loss dip

Double panel partitions with a foam core suffer a poor sound transmission loss at their mass-spring-mass resonance frequency. This paper considers the use of vibro-acoustic resonant metamaterials to improve the acoustic insulation performance at the frequency region of this resonance while adding only 8% of mass to the double panel, hence maintaining its lightweight characteristics. To design the metamaterial, dispersion curves are calculated through finite element unit cell analysis to predict the stop band frequency region. The resulting sound transmission loss due to the stop band effect is predicted using Heckl’s model combined with the equivalent dynamic mass of the metamaterial, which is obtained from the dispersion curves analysis. This method allows taking into consideration complex resonator geometries and locally reacting material interlayers in the hosting panel. The designed metamaterial double panel is realised, and its experimentally measured insertion loss surpasses the insertion loss of the bare and equivalent mass addition double panels in the targeted frequency region. The predicted insulation agrees well with the measured performance, validating the proposed method.

Dynamic mass based sound transmission loss prediction of vibro-acoustic metamaterial double panels applied to the mass-air-mass resonance

To enhance the sound insulation performance of double panel partitions at their mass-air-mass resonance frequency, novel compact and low-mass solutions are sought. This paper investigates the use of the locally resonant vibro-acoustic metamaterial concept as a possible solution. The metamaterial solution is applied to one panel of a double panel partition in order to enhance the sound transmission loss at the mass-air-mass resonance. To design the metamaterial solution and predict its sound transmission loss performance, an extension of the multiple reflection theory is proposed, incorporating the dynamic mass of a metamaterial panel. The latter is obtained from the metamaterial plate dispersion curves, calculated using finite element based unit cell modeling. The designed metamaterial solution is manufactured and its insertion loss is measured. The novel design outperforms the original double panel and an equivalent total mass double panel configuration in the targeted mass-air-mass resonance frequency region. The predictions obtained with the proposed method are in good agreement with the experimentally obtained results. This demonstrates the potential of the metamaterial solution to enhance the acoustic insulation at the mass-air-mass resonance and indicates that the proposed method allows a fast, simple and representative indication of their acoustic insulation performance.

Sound insulation of lightweight partition walls with regard to structural sound transmission

The known methods of acoustical calculation in buildings disregard the phenomenon of structural sound transmission, whereas its effect can reach from 2 to 12 dB. The purpose of this paper is to develop the calculation method for sound transmission and vibrations in connected vibroacoustic systems. Theoretical research methods were used based on the theory of statistical energy analysis (SEA) and the theory of self-consistent sound fields with regard to dual nature of sound formation - resonance and inertia. Based on M. Sedov's method of sound fields consistency, a calculation method for sound insulation was developed with integration in SEA methodology. Use of the developed method allows predicting sound transmission through a double-panel partition with the account of adjacent structures.

Active structural acoustic control of transmitted sound through a double panel partition by weighted sum of spatial gradients

Active control of harmonic sound transmission through an acoustically baffled, rectangular, simply supported double panel partition has been analytically studied. Velocity potential method is used for the vibro-acoustic modeling unlike the commonly used cavity mode method. It is very well-known that at high frequencies uncontrolled double panel partition mostly radiates sound due to the dipole-type motion of the radiating panel, which the volume velocity method can't be able to detect, therefore, weighted sum of spatial gradients is used to control these modes and achieves sound attenuation in a broad frequency band. A piezoceramic actuator (lead zirconate titanate) is attached on one side of the panel surface, and the optimal magnitude and phase of the voltage supplied to the lead zirconate titanate for minimizing the weighted sum of spatial gradients and volume velocity at the error sensor locations are calculated using a simple-gradient based algorithm. Numerical results of sound power transmission ratio and averaged quadratic velocity of panels indicate that lead zirconate titanate should be placed on the incident panel and minimization of the control quantities should be done on the radiating panel to achieve better sound attenuation. The acoustic radiation mode analysis shows that the weighted sum of spatial gradients is able to control multiple acoustic radiation modes and, thereby, accomplishes better reduction of sound power transmission compared to volume velocity.

Active control of sound transmission through a double panel partition using volume velocity and a weighted sum of spatial gradient control metrics

In this paper, active control of harmonic sound transmission through an acoustically baffled, rectangular, simply supported double panel partition has been analytically studied. Weighted sum of spatial gradients (WSSG) control metric of the radiating panel is minimized to attenuate multiple acoustic sound radiation modes and the results are compared with the minimization of volume velocity. A piezoceramic actuator (PZT) is attached on one side of the panel surface, and the optimal magnitude and phase of the voltage supplied to the PZT for minimizing WSSG and volume velocity at the error sensor locations are calculated using a simple-gradient based algorithm. Also, acoustic source arrangements are considered in the air cavity simultaneously with the structural control to further attenuate the transmitted sound power. Numerical results of sound power transmission ratio and averaged total kinetic energy of panels indicate that PZT should be placed on the incident panel to minimize the control quantities on the radiating panel. Combined WSSG and cavity control is able to control multiple acoustic radiation modes and the cavity modes and, thereby, accomplishes better attenuation in a wide frequency band.

English

In noise control applications, a double-leaf partition has been applied widely as a lightweight structure for noise insulation, such as in car doors, train bodies, and aircraft fuselages. Unfortunately, the insulation performance deteriorates significantly at mass-air-mass resonance due to coupling between the panels and the air in the gap. This paper investigates the effect of a micro-perforated panel (MPP), inserted in the conventional double-panel partition, on sound transmission loss at troublesome resonant frequencies. It is found that the transmission loss improves at this resonance if the MPP is located at a distance of less than half that of the air gap. A mathematical model is derived for the diffuse field incidence of acoustic loading.

An indirect hybrid sound transmission loss controller

The control of sound transmission through panels is an important noise control problem in the aerospace, aeronautical, and automotive industries. The trend towards using lightweight composite materials that have lower sound insulation performance is a negative factor regarding low frequency transmission loss. Double-panel partitions with the gap filled with sound absorption materials are often employed to improve the sound insulation performance with reduced added weight penalty. However, in the low frequency range, the strong coupling between the panels through the air cavity and mechanical paths may greatly reduce the sound transmission performance, making it even lower than the performance of a single panel in some frequency ranges. In this work, an experimental investigation of a new kind of hybrid (active/passive) acoustic actuator is presented. The idea consists of replacing the acoustic absorption material by a hybrid actuator aiming at improving the transmission loss at low frequencies without altering the passive attenuation. A prototype of the system is tested in a plane wave acoustic tube setup. Different kinds of SISO feedforward control implementations were used to attenuate the sound power transmitted through the hybrid active–passive panel using an error microphone or a particle velocity sensor placed downstream with respect to the sample panel. Measurement results of the transmission loss with active and hybrid attenuation are presented and discussed.

Analytical modeling of sound transmission through clamped triple-panel partition separated by enclosed air cavities

Abstract An analytical model for sound transmission through a clamped triple-panel partition of finite extent and separated by two impervious air cavities is formulated. The solution derived from the model takes the form of that for a clamp supported rectangular plate. A set of modal functions (or more strictly speaking, the basic functions) are employed to account for the clamped boundary conditions, and the application of the virtual work principle leads to a set of simultaneous algebraic equations for determining the unknown modal coefficients. The sound transmission loss (STL) of the triple-panel partition as a function of excitation frequency is calculated and compared with that of a double-panel partition. The model predictions are then used to explore the physical mechanisms associated with the various dips on the STL versus frequency curve, including the equivalent ‘mass-spring’ resonance, the standing-wave resonance and the panel modal resonance. The asymptotic variation of the solution from a finite-sized partition to an infinitely large partition is illustrated in such a way as to demonstrate the influence of the boundary conditions on the soundproofing capability of the partition. In general, a triple-panel partition outperforms a double-panel partition in insulating the incident sound, and the relatively large number of system parameters pertinent to the triple-panel partition in comparison with that of the double-panel partition offers more design space for the former to tailor its noise reduction performance.

Effectiveness of T-shaped acoustic resonators in low-frequency sound transmission control of a finite double-panel partition

Double-panel partitions are widely used for sound insulation purposes. Their insulation efficiency is, however, deteriorated at low frequencies due to the structural and acoustic resonances. To tackle this problem, this paper proposes the use of long T-shaped acoustic resonators in a double-panel partition embedded along the edges. In order to facilitate the design and assess the performance of the structure, a general vibro-acoustic model, characterizing the interaction between the panels, air cavity, and integrated acoustic resonators, is developed. The effectiveness of the technique as well as the optimal locations of the acoustic resonators is examined at various frequencies where the system exhibits different coupling characteristics. The measured optimal locations are also compared with the predicted ones to verify the developed theory. Finally, the performance of the acoustic resonators in broadband sound transmission control is demonstrated.

Sound Transmission Through Simply Supported Finite Double-Panel Partitions With Enclosed Air Cavity

Abstract The vibro-acoustic performance of a rectangular double-panel partition with enclosed air cavity and simply mounted on an infinite acoustic rigid baffle is investigated analytically. The sound velocity potential method rather than the commonly used cavity modal function method is employed, which possesses good expandability and has significant implications for further vibro-acoustic investigations. The simply supported boundary condition is accounted for by using the method of modal function and the double Fourier series solutions are obtained to characterize the vibro-acoustic behaviors of the structure. The results for sound transmission loss, panel vibration level, and sound pressure level are presented to explore the physical mechanisms of sound energy penetration across the finite double-panel partition. Specifically, focus is placed on the influence of several key system parameters on sound transmission including the thickness of air cavity, structural dimensions, and the elevation angle and azimuth angle of the incidence sound. Further extensions of the sound velocity potential method to typical framed double-panel structures are also proposed.

Modeling porous-elastic materials in periodically mount connected double panel partitions.

In aeronautic double panel partitions, the trim panel (interior panel) is usually attached to the ring frames that are ribbed to the skin panel (exterior panel) with periodically spaced resilient mounts. Moreover, porous-elastic materials are inserted in the cavity between these panels to provide absorption. Due to their periodic nature, these partitions allow the use of space-harmonic expansion formulations for their vibration and sound transmission analysis. This paper shows how equivalent fluid and porous-elastic models can be incorporated in such formulations to assess the influence of sound absorbing materials. The equations of the model are derived and simulation results are presented for materials providing different absorptions. Application is focused on the relative effects of absorption versus the mounts’ resilience on the transmission loss of the system.

Dynamic response and acoustic radiation of double-leaf metallic panel partition under sound excitation

The transmission of sound through a rectangular double-leaf metallic panel partition clamp mounted on a rigid acoustic baffle has been investigated analytically. It is found that, at a specific frequency, sound transmission through the structure is significantly enhanced for incident sound with a certain incidence angle. This physical phenomenon, namely, transparent effect, is analyzed in terms of both dynamical panel modal responses and radiating acoustic pressure. The enhanced transmission is attributed to the unique mass-air-mass effect of the double-panel partition system. Numerical results clearly demonstrate that this effect does not completely stem from the point-to-point out-of-plane motion of the two panels, due to the additional constraining effect of the clamped supports.

Analytical and experimental investigation on transmission loss of clamped double panels: Implication of boundary effects

The air-borne sound insulation performance of a rectangular double-panel partition clamp mounted on an infinite acoustic rigid baffle is investigated both analytically and experimentally and compared with that of a simply supported one. With the clamped (or simply supported) boundary accounted for by using the method of modal function, a double series solution for the sound transmission loss (STL) of the structure is obtained by employing the weighted residual (Galerkin) method. Experimental measurements with Al double-panel partitions having air cavity are subsequently carried out to validate the theoretical model for both types of the boundary condition, and good overall agreement is achieved. A consistency check of the two different models (based separately on clamped modal function and simply supported modal function) is performed by extending the panel dimensions to infinite where no boundaries exist. The significant discrepancies between the two different boundary conditions are demonstrated in terms of the STL versus frequency plots as well as the panel deflection mode shapes.

Vibroacoustic behavior of clamp mounted double-panel partition with enclosure air cavity

A theoretical study on the vibroacoustic performance of a rectangular double-panel partition clamp mounted in an infinite acoustic rigid baffle is presented. With the clamped boundary condition taken into account by the method of modal function, a double Fourier series solution to the dynamic response of the structure is obtained by employing the weighted residual method (i.e., the Galerkin method). The double series solution can be considered as the exact solution of the problem, as the structural and acoustic-structural coupling effects are fully accounted for and the solution converges numerically. The accuracy of the theoretical predictions is checked against existing experimental data, with good agreement achieved. The influence of several key parameters on the sound isolation capability of the double-panel configuration is then systematically studied, including panel dimensions, thickness of air cavity, elevation angle, and azimuth angle of incidence sound. The present method is suitable for double-panel systems of finite or infinite extent and is applicable for both low- and high-frequency ranges. With these merits, the proposed method compares favorably with a number of other approaches, e.g., finite element method, boundary element method, and statistical energy analysis method.

Double Panel Partition (AVNC) by Means of Optimized Piezoceramic Structural Boundary Control

Towards low frequencies, the sound reduction of a double panel partition has an efficiency loss. A feasibility study is investigated to improve the sound reduction of a realistic double panel partition by means of piezoelectric elements as structural control actuators between the panel boundary. Finite element modeling of the double glazing window permits an understanding of the physical phenomenon governing the vibroacoustic behavior. In particular, the incidence of the fluid cavity and the boundary conditions effects on the insertion loss factor are analyzed. Hence, an original structural control experiment has been conducted using optimized piezoceramic actuators at the double glazing window boundaries. The performances of the proposed control strategy are evaluated and it is shown that an improvement has been achieved with a simple velocity or a pressure feedback control.

Active Acoustic Control of Sound Transmission through Double Walls: Simulation Results

In this paper, the active control of sound transmission through double-panel partitions by inserting acoustic sources in the air gap between the double panels is studied through a computer simulation. The work is an extension of the previous analytical work in which a theoretical framework was developed to reveal the control mechanisms involved in active acoustic control. In this work, a computer simulation based on the theoretical framework is used to assess the control performance under different conditions. It is shown that the property of the radiating panel plays an important role in active acoustic control. The control performance can be improved by increasing the panel damping or decreasing the panel modal density. The reasons for this are discussed.