Prediction Of Sound Transmission Loss Research Articles

Prediction of Sound Transmission Loss of Vehicle Floor System Based on 1D-Convolutional Neural Networks

Prediction of Sound Transmission Loss of Vehicle Floor System Based on 1D-Convolutional Neural Networks

Broadband low-frequency sound insulation of double-panel metastructures with a perforated lattice truss-core sandwich plate

Lattice truss-core sandwich plates have drawn increasing attention owing to their excellent mechanical properties and multifunctional characteristics, but they are insufficient in low-frequency sound insulation because of their lightweight feature. To improve the sound transmission loss (STL) of such lightweight sandwich plates while without greatly increasing the structural complexity and the total mass, one faceplate of the sandwich plate is perforated so that the sandwich core can be utilized as an acoustic cavity. A homogenous plate is further introduced to construct a double-panel metastructure together with the perforated sandwich plate. For ease of analysis and design of the double-panel metastructure, a semi-analytical method is developed by combining an effective medium theory of the acoustic domain and a dynamic homogenization method of the sandwich plate. The feasibility of the developed method for efficient STL prediction under different incident angles is verified by comparing with the conventional finite element method. Numerical results show that the double-panel metastructure exhibits a remarkable sound insulation performance within a broadband low-frequency range, owing to the fact that the acoustic domain enclosed by the double-panel metastructure has an unusual equivalent bulk modulus. Then, a parametric study is conducted to reveal the sound insulation capacity and provide a guideline for tuning the STL of the double-panel metastructure. Finally, the actual sound insulation capacity of the double-panel metastructure is validated by experimental measurements of large-scale specimens.

Prediction of sound transmission loss of hemispherical shell using statistical energy analysis and its experimental validation

The hemispherical shells are broadly used in many industries and applications such as aerospace, submarines, tanks, and architectural structures. Sound transmission loss prediction of such structures is essentially required during the design and assessment phases from the acoustic point of view. In the present paper, sound transmission loss of the hemispherical shell is predicted analytically and validated experimentally. The Statistical energy analysis (SEA) technique is employed to formulate an analytical model for computing the sound transmission loss of a hemispherical shell across a wide frequency range. The sound intensity experimental method was used to verify the proposed SEA formulation. The analytical predictions and the measured transmission loss were found to be in good agreement. Based on the proposed SEA model, the influence of design parameters such as the absorption coefficient, thickness, radius, and different materials on the transmission loss was investigated.

Prediction of sound transmission loss of conical acoustic enclosure using statistical energy analysis and its experimental validation

The conical shape structures are widely employed in many practical applications such as aircraft, rockets, tanks, and submarines. Prediction of sound transmission loss is often required at the design and evaluation stages of such structures. In this paper, an analytical model is proposed using the statistical energy analysis (SEA) technique to predict the sound transmission loss of a conical shape acoustic enclosure in a broad frequency range. The proposed model is verified experimentally using the sound intensity experimental technique. It was found that the analytical predictions are in good agreement with the measured transmission loss, specifically at the ring and critical frequencies. The percentage error between predicted and measured lower ring frequency is 5.1% and that for the upper ring frequency is 0.4%. The percentage error between predicted and measured critical frequency is 2.7%. The results obtained indicate that the developed analytical model can be used as an efficient design tool to predict the acoustic performance of conical shape structures.

Prediction of sound transmission loss of cylindrical acoustic enclosure using statistical energy analysis and its experimental validation.

In the present work, the sound transmission through a cylindrical shape acoustic enclosure is predicted analytically and verified experimentally. An analytical model is developed, based on the statistical energy analysis (SEA) approach, to examine the transmission loss of a cylindrical acoustic enclosure in different frequency regions, including the low-, intermediate-, and high-frequency ranges. In the developed model, the nonresonant wave response is included in addition to consideration of the resonant response for obtaining more accurate results. It is demonstrated that the developed SEA formulation in this work can compute the resonant as well as the nonresonant sound transmission of the cylindrical acoustic enclosure separately. To validate the analytical model, an experimental setup was developed, and the sound transmission loss of a cylindrical acoustic enclosure was measured using the sound intensity experimental technique. It was found that the analytical results are in good agreement with the measured transmission loss, especially at the panel ring and critical frequencies. The results obtained indicate that the proposed analytical model is efficient to predict the sound transmission loss of cylindrical acoustic enclosures.

Sound Transmission Prediction of Sandwich Plates With Honeycomb and Foam Cores and an Emphatic Discussion on Radiation Terms

When applying the modal summation method to the sound transmission loss (STL) prediction of various plates, the assumption of the blocked sound pressure, or alternatively speaking, ignoring sound radiation terms, has obvious simplicity and is sometimes used for the single-layered panels, rib-stiffened plates or heavily damped sandwich plates. For light-weighted sandwich plates with honeycomb and foam cores, however, this assumption is somewhat in doubt and worth examining. Based on sixth-order differential equations governing the flexural vibration of sandwich plates, the prediction formula of STL is derived by the modal summation approach. Theoretical predictions were validated by measurement data. Next, the theoretical formula of STL under the assumption of the blocked sound pressure was examined. The STL discrepancies of sandwich plates caused by sound radiation terms are illustrated. It was found that the STL discrepancies of sandwich plates were closely related to frequency, reached their peak value at the coincidence frequency region. The results indicate that the sound radiation terms, or the couplings between the radiated sound pressure and the plate response, should not be ignored for the prediction of STL for sandwich plates with honeycomb and foam cores.

Prediction of sound transmission loss of exhaust system particulate filter by homogenization method

Prediction of sound transmission loss of exhaust system particulate filter by homogenization method

Microstructural modeling of porous ceramic materials by homogenization method and prediction of sound transmission loss of particulate collection filter

Microstructural modeling of porous ceramic materials by homogenization method and prediction of sound transmission loss of particulate collection filter

Effects of mounting positions and boundary conditions on the sound transmission loss of panels in a niche

The sound insulation performance of railway car body structures is critical for the control of rail vehicle interior noise. In sound transmission loss (STL) measurements, a niche with a large depth is necessary to allow for mounting the wide range of thicknesses of railway car body panels and for the mechanical isolation of the two rooms. In this study, two typical interior floor panels are tested in a series of mounting conditions and mechanical boundary conditions. The change of STL results during measurement is also predicted by an STL prediction model based on the finite element method. At lower frequencies, the STL results are influenced by both the mounting positions and the mechanical boundary conditions. At higher frequencies, the STL results are mainly influenced by the mechanical boundary conditions. Differences between the panel in the infinite baffle and niches at the resonance and off-resonance frequencies are different. Considering both the effects of mounting positions and mechanical boundary conditions, the existence of the cavity amplifies the STL difference caused by the mechanical boundary conditions.

Lightweight design and sound insulation characteristic optimisation of railway floating floor structures

The sound insulation performance of extruded panels used in railway vehicles is critical to control the interior noise, especially in the case of floor panels. To reduce the mass of floating floors and increase its sound insulation performance, a lightweight design instruction approach has been proposed based on the vibration response of each component of the floating floor structures. The total height, length, thickness of the top layer, thickness of the ribs, and thickness of the bottom layer in the typical cross section of the exterior floor are used as variables; the mass of the typical cross section and the averaged sound transmission loss (STL) results in 1/3 octave bands centred from 400 to 3150 Hz are used as the optimisation targets; the optimal result of the smallest mass and the largest averaged STL are achieved in commercial software VA One and Isight. The effect of this optimisation scheme on the sound insulation performance of the floating floor is analysed based on the verified STL prediction model. After this optimisation, the results indicate that the mass of the exterior floor structure is reduced by 15.2% compared with the original exterior floor structure, and the averaged STL in 1/3 octave bands centred from 400 to 3150 Hz and the weighted STL of the floating floor are increased by 0.8 dB and 1 dB, respectively.

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.

Effects of external and air gap flows on sound transmission through finite clamped double-panel sandwich structures

In this paper, previous theories on the prediction of sound transmission loss (STL) through a finite clamped double-panel sandwich structure lined with poroelastic material are extended to address the influence of both external and air gap flows. Biot’s theory is employed to describe wave propagation in poroelastic material. The clamped boundary condition along the panel edge introduces the modal superposition theory and a double Fourier series solution for the STL is obtained by employing the weighted residual (Galerkin) method. The analytical model is validated against theoretical results of a single incident wave under normal and oblique incidences. Various parameters such as flow velocity and gap flow orientations are considered. The numerical results suggest that the STL performance can be enhanced dramatically below the fundamental (1,1) resonance frequency with the increasing gap flow Mach numbers. Opposite orientation of air gap flows further improve the STL in the low-frequency range, and reduces the limiting angle of incidence which can trigger total internal reflection across the panel system. Although the air gap flows have less influence than the external flow, their noticeable effects on the STL show the potential in active/passive noise control.

An efficient analytical model for baffled, multi-celled membrane-type acoustic metamaterial panels

A new analytical model for the oblique incidence sound transmission loss prediction of baffled panels with multiple subwavelength sized membrane-type acoustic metamaterial (MAM) unit cells is proposed. The model employs a novel approach via the concept of the effective surface mass density and approximates the unit cell vibrations in the form of piston-like displacements. This yields a coupled system of linear equations that can be solved efficiently using well-known solution procedures. A comparison with results from finite element model simulations for both normal and diffuse field incidence shows that the analytical model delivers accurate results as long as the edge length of the MAM unit cells is smaller than half the acoustic wavelength. The computation times for the analytical calculations are 100 times smaller than for the numerical simulations. In addition to that, the effect of flexible MAM unit cell edges compared to the fixed edges assumed in the analytical model is studied numerically. It is shown that the compliance of the edges has only a small impact on the transmission loss of the panel, except at very low frequencies in the stiffness-controlled regime. The proposed analytical model is applied to investigate the effect of variations of the membrane prestress, added mass, and mass eccentricity on the diffuse transmission loss of a MAM panel with 120 unit cells. Unlike most previous investigations of MAMs, these results provide a better understanding of the acoustic performance of MAMs under more realistic conditions. For example, it is shown that by varying these parameters deliberately in a checkerboard pattern, a new anti-resonance with large transmission loss values can be introduced. A random variation of these parameters, on the other hand, is shown to have only little influence on the diffuse transmission loss, as long as the standard deviation is not too large. For very large random variations, it is shown that the peak transmission loss value can be greatly diminished.

Evaluation of a hybrid TMM-SEA method for prediction of sound transmission loss through mechanically coupled aircraft double-walls

This paper presents a detailed experimental validation of a hybrid TMM (transfer matrix method)/SEA (statistical energy analysis) method to predict the sound transmission through mechanically coupled aircraft double-walls. The accuracy of the model is investigated using lightweight structures representative of a composite aircraft fuselage cross-section over a large frequency band. The studied structure is composed of a thick composite sandwich panel representative of primary structure, lined with an acoustic insulation layer (glass wool), and structurally connected via vibration isolators to a thin composite sandwich lining panel representative of an interior trim panel. Three types of vibration isolators are considered: a soft, stiff and rigid mechanical links. Results show that the transfer matrix model is able to predict changes in the overall transmission caused by different structural couplings. Modelling limitation is mainly traced to the uncertainties in the measurement of the dynamic stiffness of vibration isolators which are directly propagated to the coupling loss factor and, therefore, to the transmission loss.

A Combined Experimental and Analytical Approach for the Simulation of the Sound Transmission Loss of Multilayer Glazing Systems

In order to ensure acoustic comfort of living spaces, nowadays façade systems having high performance are required. Within such context the glazing systems play a key role in achieving high levels of sound insulation. The characteristics of sound insulation of such systems can be determined by analytical methods that make use of experimental characterizations of the physical and mechanical parameters of these systems. In this work a combined experimental and analytical approach for sound transmission loss prediction of glazing systems is presented. In particular, the mechanical properties of monolithic and multilayer glasses with viscoelastic interlayer made of polyvinyl butyral (PVB) are measured using resonance curve method of flexural waves on glass beams with different boundary conditions. In order to achieve reliable input mechanical data (Young's modulus and loss factor), tested beams are characterized in free-free and elastic constraints boundary conditions, respectively. The elastic constrain boundary conditions are realized following the same specifications of ISO Standard 10140 series for larger panels. Starting from the proposed mechanical characterization, the diffuse field sound transmission loss of glass panels has been predicted through an analytical model for solid elastic layers. Results from the above-mentioned procedure are compared with laboratory measurements. From the analysis it will be shown a better accuracy in determining the sound transmission loss of panels when the elastic constrain boundary conditions are applied to the representative beams.

Low frequency sound insulation analysis and evaluation of stiffened building structures

The sound transmission loss (STL) of a stiffened building structure is investigated using a coupled finite element and boundary element method. This STL prediction method takes into account both the effects of boundary condition and the stiffener and allows for an efficient computation of a plate structure with arbitrary boundary conditions and with arbitrary located stiffeners. Experimental measurements with a stiffened plate system are carried out to validate the proposed prediction method. The predictions agree well with the experimental data. The stiffened plate system designed for the experiment has the attraction of simplicity and flexibility and could be a good example for the design of a practical stiffened building structure. A single-number rating method is also proposed for the assessment of structural sound insulation. The rating procedure is similar to the international standard ASTM E413-10, but new reference contours are defined to make the method suitable for sound insulation assessment in the low-frequency range. The proposed methods are subsequently applied to parametric studies that examine the effects of the stiffener on the sound insulation performance of practical glass structures. The possibility of improving sound insulation performance of a building structure by using the stiffener is thereby demonstrated.

Sound transmission through triple-panel structures lined with poroelastic materials

In this paper, previous theories on the prediction of sound transmission loss for a double-panel structure lined with poroelastic materials are extended to address the problem of a triple-panel structure. Six typical configurations are considered for a triple-panel structure based on the method of coupling the porous layers to the facing panels which determines critically the sound insulation performance of the system. The transfer matrix method is employed to solve the system by applying appropriate types of boundary conditions for these configurations. The transmission loss of the triple-panel structures in a diffuse sound field is calculated as a function of frequency and compared with that of corresponding double-panel structures. Generally, the triple-panel structure with poroelastic linings has superior acoustic performance to the double-panel counterpart, remarkably in the mid-high frequency range and possibly at low frequencies, by selecting appropriate configurations in which those with two air gaps in the structure exhibit the best overall performance over the entire frequency range. The poroelastic lining significantly lowers the cut-on frequency above which the triple-panel structure exhibits noticeably higher transmission loss. Compared with a double-panel structure, the wider range of system parameters for a triple-panel structure due to the additional partition provides more design space for tuning the sound insulation performance. Despite the increased structural complexity, the triple-panel structure lined with poroelastic materials has the obvious advantages in sound transmission loss while without the penalties in weight and volume, and is hence a promising replacement for the widely used double-panel sandwich structure.

크루즈선박용 허니컴 패널의 차음 성능 해석

본 연구에서는 허니컴 패널의 지배방정식을 이용하여 경계행렬식을 유도하였고, 이를 전달행렬법에 적용하여 허니컴 패널을 적용한 차음패널에 대한 해석 이론을 정립하였다. 또한, 허니컴 패널을 선박용 차음패널의 표면재로 적용하여 차음성능을 분석하였고, 철판을 표면재로 적용한 기존의 선박용 차음패널과 차음성능을 무게 당 감음량 기준으로 비교 분석하였다. 그 결과, 허니컴 패널의 차음성능이 0.35 mm 철판에 비해 STC 기준으로 2dB 높게 나와 허니컴 패널을 적용한 차음패널의 차음성능이 철판을 사용한 차음패널에 비해 무게 당 감음량을 고려할 시 우수하다는 것을 확인하였다. 또한, 허니컴 패널을 표면재로 사용한 차음패널의 면밀도가 철판을 사용한 차음패널에 비해 약 <TEX>$5.2kg/m^2$</TEX> 가볍게 나타났고, 이는 약 31.7 % 무게 감소를 의미한다. In this paper, the interface matrix of honeycomb composite panel has been derived by the governing equation of a honeycomb sandwich panel. The interface matrix of honeycomb panel is added to the previously developed transfer matrix method, thus analysis of the multi-layered insulation composite panel with honeycomb is accomplished. Furthermore, predictions of sound transmission loss(STL) for the ship's insulation panel with honeycomb and mineral wool are presented. The insulation performance of the honeycomb used for skin of the ship's insulation panel is better than that of 0.35 mm steel panel by 2dB, approximately. Although honeycomb panel has inefficient insulation performance beside steel panel, honeycomb panel achieve improvements in the performance of weight reduction. The surface density of the panel with honeycomb is rather than with steel by <TEX>$5.2kg/m^2$</TEX>. It is decrease in weight by 31.7 %.

Determining sound transmission through damped partitions: Challenges in theoretical prediction and laboratory testing

The sound transmission loss through traditional wall and ceiling building partitions can currently be predicted using software programs and/or laboratory test data. There is, however, a great divide that separates the theoretical prediction of sound transmission loss from the laboratory-measured values. Some of the most common prediction software packages do not account for dynamic (frequency- and temperature-dependent) material properties and are, therefore, incapable of predicting sound transmission accurately for some common solutions. The most accurate and precise software prediction tools available become impractical because the cross-correlation between laboratory testing facilities is so poor that it is not possible to replicate predicted performance dynamics in a laboratory setting. Using the structural properties of damping materials as an example, the divide between theoretical prediction and laboratory testing will be illustrated and possible solutions for closing such a divide will be presented.

Prediction of Sound Transmission Loss for Finite Sandwich Panels Based on a Test Procedure on Beam Elements

An approach on the prediction of sound transmission loss for a finite sandwich panel with honeycomb core is described in the paper. The sandwich panel is treated as orthotropic and the apparent bending stiffness in two principal directions is estimated by means of simple tests on beam elements cut from the sandwich panel. Utilizing orthotropic panel theory, together with the obtained bending stiffness in two directions, the sound transmission loss of simply-supported sandwich panel is predicted by the modal expansion method. Simulation results indicated that dimension, orthotropy, and loss factor may play important roles on sound transmission loss of sandwich panel. The predicted transmission loss is compared with measured data and the agreement is reasonable. This approach may provide an efficient tool to predict the sound transmission loss of finite sandwich panels.