Acoustic Contribution Analysis Research Articles

Low noise optimization of two-stage gearbox housing structure based on acoustic contribution analysis and topology optimization

Low noise optimization of two-stage gearbox housing structure based on acoustic contribution analysis and topology optimization

Experimental and numerical investigation on the vibro-acoustic characteristics of periodic rib stiffened plate based on band gap theory

This study presents a novel method for analyzing the vibration and noise from the periodic rib stiffened plate (PRSP). For the first time, the band gap theory was combined with hybrid finite element-boundary element method (FE-BEM) to predict the vibro-acoustic characteristics of this structure and guide its vibration and noise reduction design from the perspective of bending wave propagation. The excitation test was carried out simultaneously to verify the rationality and accuracy of the proposed method. Then, the acoustic contribution analysis was conducted and the influence of structural design parameters on bending wave bandgap and noise reduction effect was discussed in detail. The results show that there are alternating passbands and stopbands for bending waves propagating in PRSP, making the vibro-acoustic responses in different frequency bands exhibit distinct differences as well. Increasing the base plate thickness and decreasing the rib spacing are conducive to widen the bandgaps and reduce the noise radiation, which are the decisive factors affecting the vibro-acoustic characteristics of PRSP. While the rib thickness has little effect, this provides a new approach for vibration mitigation and acoustic optimization in steel bridges.

Panel Acoustic Contribution Analysis in Automotive Acoustics Using Discontinuous Isogeometric Boundary Element Method

In automotive industries, panel acoustic contribution analysis (PACA) is used to investigate the contributions of the body panels to the acoustic pressure at a certain point of interest. Currently, PACA is implemented mostly by either experiment-based methods or traditional numerical methods. However, these schemes are effort-consuming and inefficient in solving engineering problems, thereby restraining the further development of PACA in automotive acoustics. In this work, we propose a PACA scheme using discontinuous isogeometric boundary element method (IGABEM) to build an easily implementable and efficient method to identify the relative acoustic contributions of each automotive body panel. Discontinuous IGABEM is more accurate and converges faster than continuous BEM and IGABEM in the interior sound pressure evaluation of automotive compartments. In this work, a contribution ratio is defined to estimate the relative acoustic contribution of the structure panels; it can be calculated by reusing the coefficient matrix that has already been generated in the sound pressure evaluation process. The utilization of the parallel technique enables the proposed method to be more efficient than conventional methods; it is validated in two numerical examples, including a car passenger compartment subjected to realistic boundary conditions. A sound pressure response experiment based on a steel box is conducted to verify the accuracy of the interior sound pressure calculation using discontinuous IGABEM. This work is expected to promote the practical process of IGABEM for application in automotive acoustic problems.

Optimal Design and Experimental Verification of Low Radiation Noise of Gearbox

Reducing the radiated noise of a gearbox is a difficult problem in aviation, navigation, machinery, and other fields. Structural improvement is the main means of noise reduction for a gearbox, and it is realized primarily through contribution analysis and structure optimization. However, these approaches have certain limitations. In this study, a low-noise design method for a gearbox that combines the two approaches is proposed, and experimental verification is performed. First, a finite element/boundary element model is established using a single-stage herringbone gearbox. Considering the vibration excitation of the gear system, the radiation noise of a single-stage gearbox is predicted based on the modal acoustic transfer vector (MATV) method. Subsequently, the maximum field point of the radiated noise is determined, and the acoustic transfer vector (ATV) analysis and modal acoustic contribution (MAC) analysis are conducted to determine the region that contributes significantly to the radiated noise of the field point. The optimization region is selected through the panel acoustic contribution (PAC) analysis. Next, to reduce the normal speed in the optimization region, topology optimization is performed. According to the topology optimization results, four different noise reduction structures are added to the gearbox, and the low-noise optimization models are established respectively. Finally, by measuring the radiated noise of the gearbox before and after optimization under a given working condition, the validity of the radiated noise prediction method and the low-noise optimization design method are verified by comparing the simulation and experimental data. A comparison of the four optimization models proves that the noise reduction effect can be achieved only by adding a noise reduction structure to the center of the density nephogram.

A new method for location of the main contribution modes by the decomposed sound pressure

The control of loud structure-borne noise inside car cabins is commonly by analyses such as panel acoustic contribution analysis, sensitivity analysis, and optimization analysis, to find suitable and practical structural modifications. However, these analyses are usually repeated dozens of times before accessing effective structural modifications, which requires more computation and time. This paper presents a new way to decompose sound pressure and quickly locate structural and acoustic modes of the main contribution for efficient access of feasible structural modifications. The decomposition process of the sound pressure inside structure-acoustic coupled systems was summarized by analyzing specific mathematical formulas. The details for locating the structural and acoustic modes of the main contribution by the decomposed sound pressure were investigated, taking a typical structure-acoustic coupled system of a rigid box with one flexible wall at bottom as an example. To evaluate the correctness of the main contribution modes, modifications were suggested in the structural modes of the main contribution, based on the mechanics of structure-acoustic coupling. The results indicated that the interior sound pressures of structure-acoustic coupled systems are decomposed into matrices by certain mathematical formulas. The main contribution modes are located by analyzing larger data in the decomposition matrices. The modifications in the structural modes of the main contribution reduce the corresponding sound pressure, which shows the correctness of the main contribution modes found. Furthermore, one way for quick suggestion of effective structural modifications was proposed, which offers a potential option for the reduction of structure-borne noise inside car cabins.

Study on broad flexural wave bandgaps of piezoelectric phononic crystal plates for the vibration and noise attenuation

This paper explores a new approach to reducing the interior noise of one vehicle body through the flexural wave bandgap. The phononic crystal is designed by attaching the periodic piezoelectric stacks with the shunting circuits on the host plate. To better implement the frequency-dependent properties, the theoretical model of the piezoelectric stack is improved through capacitance identification. On this basis, the plane wave expansion method is employed to calculate the bandgap. An ultra-wide bandgap is achieved by tuning the shunting circuits and confirmed via the finite element method. The influence of electrical parameters on flexural wave attenuation is investigated. The applicability of the presented resonators for different host plates under the presented design guideline is examined. Subsequently, the concept of phononic crystal with the unique bandgap is exploited to enhance the interior sound performance of one vehicle body. Combining the sound response analysis with the panel acoustic contribution analysis, the numerical study is performed to pick out the critical panels for the arrangement of resonators. Then a circuit control strategy is proposed to activate the wide bandgap. The results demonstrate that the present piezoelectric phononic crystal plate has a significant advantage in hindering the flexural wave propagation and suppressing structure-borne noise over a broadband low-frequency range.

Multi-objective optimization of gearbox based on panel acoustic participation and response surface methodology

Aiming at noise problem of two-stage gearbox, this paper uses the panel acoustic contribution analysis (PACA) and response surface methodology to conduct structural-borne acoustics analysis and multi-objective optimization of gearbox. Using this optimization, optimal layout and parameters of the added ribs can be determined. The dynamic model of a spur gear-shaft-bearing system is built in consideration of the time-varying mesh stiffness, the time-varying bearing stiffness, and the flexibility of the shaft, while dynamic load of the bearing is obtained through solving the model. The dynamic load of bearings is considered as excitation to analyze the vibration and noise radiation characteristics of housing. Furthermore, acoustic transfer vector, modal acoustic contribution and PACA are used to select the region with the most acoustic contribution. The variable ribs structure model (VRSM) is established in this region. Finally, the VRSM are adopted to optimize the housing. The optimization model based on the peak sound pressure level (PSPL) and the ribs mass (Rm) is established by using response surface method. Through multi-objective optimization, the variable in VRSM can be modified or deleted to reduce the radiated noise of the gearbox. The optimization results demonstrate that the PSPL after optimization is decreased by 4.88 dB at frequency of 3130 Hz. At the same mass, the noise reduction effect of VRSM is 12% higher than that of standard rib. Therefore, the optimization effect of the housing structure is obvious. PACA-VRSM-RSM- NSGA-II technology provides a new research scheme for reducing the vibration and noise of the gearbox.

Structure-borne noise of fully enclosed sound barriers composed of engineered cementitious composites on high-speed railway bridges

Fully enclosed sound barriers (FESBs) have been gradually introduced to sensitive sections alongside high-speed railways because of greater noise mitigation compared with vertical sound barriers. However, metal sound insulation boards (SIBs) commonly used in FESBs have poor durability and high cost, and prominent vibration problems induced by high-speed passing trains can lead to deformation fatigue damage of structural components of FESBs, and also bring about vibroacoustic radiation, namely, structure-borne noise. To reduce the defects of metal SIBs, high-strength and tough low-viscosity concrete SIBs with engineered cementitious composite (ECC) has been developed. To determine the characteristics of structure-borne noise generated by ECC FESBs arranged on high-speed railway bridges (HSRB) and their influence on the acoustic environment alongside the track line, systematic field tests were implemented targeting the vibration and noise of FESBs. A validated numerical model of structure-borne noise was formulated using the fast multipole boundary element method (FMBEM). The time–frequency distribution characteristics and the correlation between vibration and structure-borne noise are thoroughly analyzed. The structure-borne noise of HSRBs with ECC FESB, metal FESB and without FESB were compared, and the influences of ECC FESB at typical points in the acoustic field were quantified using panel acoustic contribution (PAC) analysis. The variation in the structure-borne noise with train speed were also examined. Results showed that the structure-borne noise radiation to the acoustic field were changed owing to the installation of FESBs, and the overall sound pressure level (OSPL) increased by 2.3 dB near the bridge components, 12.8 dB at 1.2 m above the ground, and 19.5 dB above the track. The structure-borne noise of ECC FESBs has become the main acoustic contributor in acoustic field and accounts for 64.1% and 82.7% for locations above the ground and for the points which are horizontally above the track’s center line at a distance of 25 m, respectively. The structure-borne noise of ECC FESB is higher than that of metal FESB by less than 1.4 dB. The OSPL of ECC FESB on the bridge increased by approximately 1.4 dB following a train speed increase of 20 m/s. This research is anticipated to be used as a reference in future studies of the acoustic characteristics of structures with large volumes using new materials.

Optimization of Noise Transfer Path Based on the Composite Panel Acoustic and Modal Contribution Analysis

The noise of a cab directly affects the comfort and labor efficiency of the operators. The optimization of the structure-borne transmission path can obviously reduce the cab noise. The method of panel acoustic contribution analysis (PACA) is used to reduce structure noise. However, most studies only consider the panel acoustic contribution of a single frequency, without considering the contribution of major frequencies synthesis to confirm the optimized panels. In this paper, a novel method is proposed based on composite panel acoustic and modal contribution analysis and noise transfer path optimization in a vibro-acoustic model. First, the finite element model (FEM) and the acoustic model are established. Based on the acoustic transfer vector (ATV) method, a composite panel acoustic contribution analysis method is proposed to identify the panels affecting the noise of the field point. Combined with the modal acoustic contribution of the modal acoustic transfer vector (MATV) method, the noise field point is confirmed in the area which has the most significant influence. Second, the optimization algorithm NLOPT which is a nonlinear optimization is applied to design the areas. The noise transfer path optimization with vibroacoustic coupling response can quickly determine the optimal thickness of the panels and reduce low-frequency noise. The effectiveness of the proposed method is applied and verified in an excavator cab. The sound pressure level (SPL) the driver’s right ear (DRE) decreased obviously. The acoustic analysis of the composite panel acoustic contribution and modal acoustic contribution can more accurately recognize an optimized area than the traditional PACA. This method can be applied in the optimization of the structure-borne transmission path for construction machinery cab and vehicle body.

Research on multi-band structural noise reduction of vehicle body based on two-degree-of-freedom locally resonant phononic crystal

First, the dispersion curve of a two-degree-of-freedom locally resonant phononic crystal (LRPC) is calculated by the plane wave expansion method. The result shows that the structure has the characteristics of double bandgaps in the mid- and low-frequency range, which is verified by the finite element method. Then, the frequency response analysis of the interior noise and the acoustic contribution analysis of car panels are carried out, and the front left floor is found out to be the panel with a larger contribution of the peak value of noise. Therefore, the LRPC is arranged on the front left floor based on the modal strain energy, and then the total vibration level and the radiated sound power level of the panel are calculated, which are both decreased by 11 dB to 13 dB after the arrangement of LRPC. The acoustic simulation analysis of the whole vehicle after the arrangement is also carried out, which shows that the original sound pressure level peaks at 270 Hz, 346 Hz and 378 Hz are reduced by 6.2 dB(A), 5.56 dB(A) and 9.35 dB(A), respectively. The results provide guidance for the application of LRPC in the field of structural noise reduction of engineering plates.

Noise simulation and low noise design of skinned panel structure of scientific experiment rack

The noise of the scientific experiment rack radiates into the space station through the skinned structure, which directly affects the safety and health of astronauts in orbit for a long time, so it is necessary to carry out low-noise design. Firstly, the finite element model of the panel structure is established, and the correctness of the model is verified by modal test. Secondly, select a point as the vibration excitation point on the finite element model of the plate structure to simulate the vibration input of the excitation source, obtain its vibration response through the modal superposition method, take the vibration response as the boundary condition of the acoustic boundary element, use the modal acoustic transfer vector technology to calculate the radiation noise of the plate structure, and verify it through the noise test in the half anechoic chamber. Then, the acoustic pressure contribution analysis of the radiated noise from the skinned panel structure is carried out, and the panel area which can reduce the radiated noise of the target is determined. The constrained damping layer is applied in this area. The results show that the radiated noise at the target position is significantly reduced.

Numerical study of volute casing vibro-acoustics in a marine centrifugal fan

ABSTRACT A numerical parametric optimization of a vibro-acoustic coupling method that considered the influence of vibro-acoustic coupling was carried out to investigate the casing vibrations and feathers of vibrational noise induced by unsteady flow of the marine centrifugal fan at the best-efficiency point (BEP). There are three important aspects of this method. First, an unsteady flow-field with a whole impeller-volute configuration was solved to obtain the source of the vibro-acoustics. Second, a fluid-structure-acoustic coupled method was implemented to study the volute vibrations and behaviours of vibrational noise. Besides, the generation mechanism of vibrational noise of the volute casing was also revealed. Moreover, the positions of the noise source of the volute casing was studied and revealed applying the panel acoustic contribution analysis (PACA) method. Third, the panel thicknesses of the volute casing (such as front-panel thickness [FT], side-panel thickness [ST], and back-panel thickness [BT]) were defined as design variables, and the outlet acoustical power of the volute casing surface was also defined as an optimal target function. Then, the parametric analysis method was used to explore the parametric relationship between the two. Fan aerodynamic performance, volute casing surface fluctuations, and vibrations were validated by experiments, and showed good agreement. The parametric analysis provides a reasonable range of values of three panel thicknesses that result in minimal vibrational sound radiation.

Vibration reduction of car body based on 2D dual-base locally resonant phononic crystal

Due to the coating feature and bandgap adjustability of dual-base locally resonant phononic crystal (LRPC), the purpose behind this paper is to explore the application of dual-base LRPC in vibration reduction of car body. In previous research, the band structure and its influencing factors of dual-base LRPC have been investigated theoretically. As an artificial periodic structure, the key factors of application, including the number of unit cells, the curvature of base panel and the boundary constraint, have been taken account into analyzing bandgap characteristics of dual-base LRPC by finite element method (FEM). The results indicate that the non-infinite dual-base LRPC structure with small curvature and boundary constraint can still produce the expected bandgap. Then, according to the acoustic contribution analysis, the floor has been determined as the target panel for vibration reduction, on which the dual-base LRPC has been conducted. In order to obtain the wider bandgap with less added mass, the lattice constant and stiffness have been matched and optimized. With the final arrangement, the total body vibration level sharply reduces by 15 dB, and the interior noise reduces by 9 dB as well. It provides a new method for the vibration reduction of car body.

Low-noise structure optimization of a heavy commercial vehicle cab based on approximation model

Structure design for reducing noise is essential and widely studied because cab interior noise seriously affects the ride comfort of the driver and passengers, especially for heavy commercial vehicles. This paper proposes an enhancement investigation on the low-noise structure performance of a cab in a heavy commercial vehicle based on an approximation model. A series of vibroacoustic tests with varying running speeds are implemented first to acquire the vibration signals at four cab suspensions and the sound pressure signal at the right ear of the driver. The finite element model and structure–acoustic coupled model of the cab of a heavy commercial vehicle are established sequentially. When the vibration accelerations measured in the tests are converted into excitation signals using the cab structure–acoustic coupled model, the sound pressure of the right ear of the driver is predicted, and the accuracy of the cab structure–acoustic coupled model is then verified. After panel acoustic contribution analysis, an approximation model of critical panel thickness and the peak noise near the right ear of the driver is established in accordance with the radial basis function. Genetic algorithm is utilized to solve an optimization model to obtain optimal panel thicknesses. By comparing the right ear sound pressure before and after optimization, the results confirm that optimized panel thicknesses can reduce sound pressure level of the critical frequency.

Panel Contribution Analysis Based on FEM, BEM and Numerical Green’s Function Approaches

The panel acoustic contribution analysis is used to determine the contribution of vibrating panels to the noise level inside closed spaces like a car cabin. The use of numerical techniques makes it possible to rate the panels according to their contributions accounting for the interaction between the structural vibrations and the acoustic pressure at a listening point. We consider the application of the finite and boundary element methods and the numerical Green’s function approaches to the problem and discuss the pros and cons regarding their use. The results show that the numerical Green’s function approach coupled to structure can be effectively used for the panel contribution analysis in situations with multiple panels and few listening points.

An investigation on interior noise reduction using 2D locally resonant phononic crystal with point defect on car ceiling

Interior noise, as one of the indicators of automotive NVH (noise, vibration and harshness) performance, has been associated with an increasing importance in ride comfort evaluation. This paper presents a new method of interior noise reduction based on phononic crystal theory. Considering the lightweight requirement, the car ceiling plate is divided into nine regions to determine where the phononic oscillators should be mounted. By leveraging the acoustic contribution analysis of each region, the phononic crystal is arranged in the region that contributes the most to interior noise, bringing out the best attenuation effect in its bandgap. However, it is noted that at certain frequencies, the vibration of the ceiling plate or other body plates, which exhibits negative contribution to interior noise, should not be attenuated due to their beneficial effects. Thus in this paper, a point defect is employed for the design of a two-dimensional (2D) phononic crystal structure to preserve the negative contribution part of the plate’s vibration at specific frequencies. The validity of the proposed method in interior noise reduction is verified by simulation. Moreover, the error analysis is implemented and an optimization scheme is proposed.

Identification and contribution analysis of vehicle interior noise based on acoustic array technology

This article proposes an advanced far-field acoustic hologram for vehicle sound source identification and investigates a method of performing contribution analyses in the far field. The hologram is applied for statistically optimized near-field acoustic holography used to identify vehicle sound sources (internal and external). An advanced far-field acoustic hologram is first proposed to improve the spatial resolution of low-frequency sound source locations in the far field. In addition, an acoustic contribution analysis based on near-field acoustic holography is used to provide a direction for low-noise optimization design. Next, a new sound source identification and low-noise technology is explored via the aforementioned methods and applied for sound source identification and acoustic contribution analyses for a vehicle. The analysis results showed that in the process of sound source identification, the contribution of each sound source can be simultaneously sorted, and this finding can help guide research on the low-noise control of a vehicle.

The Analysis of the Influence of Cab Structure to Noise Under Random Excitation

The vibration and acoustic coupling FEA of light truck cab is established using the combining way of experiment and finite element simulation in this paper. The influence of cab structure to noise under random excitation is studied by acoustic plates contribution analysis. Extract a sound pressure level of the points beside driver’s right ear. Finally, the plates that contribution a lot to acoustic are respectively front windshield, the left door, left side window, the top cover, rear floor and the front floor which provides a reference for the improvement of the cab acoustic environment in the future.

Optimal rib layout design for noise reduction based on topology optimization and acoustic contribution analysis

In this paper, an optimum rib layout design method for reducing radiated noise is proposed based on topology optimization and acoustic contribution analysis. According to radiated noise depends on acoustic transfer vector (ATV) and normal velocity, the influence of rib layout on ATV is analyzed and it is found rib layout has little influence on ATV. Only if a region has maximum acoustic contribution, the normal velocities on this region can have the most remarkable influence on radiated noise. So the determination procedure of region with maximum acoustic contribution is introduced. Based on this, the topology optimization model is established to minimize the normal velocities on this region. Ribs can be arranged according to the optimum topologies to reduce the normal velocities, which in turn results in a reduction of radiated noise. The topology optimization model is used to obtain the optimal rib layout by taking a plate-like structure as an example. The plate is fixed along all side edges and excited by a time-harmonic external point load with different prescribed frequencies. The radiated noise is simulated using the finite element method and boundary element method. Four plates are manufactured according to the optimal rib layouts for different single frequency excitation. Modal test and sound measurement are conducted to validate the proposed method. The influence of loading position on the topology optimization results is also investigated and discussed.

Analysis on the Acoustic Contribution of the High Speed Train Car Body Panels

High speed train interior structural noise which caused by vibration of car body panels influence passengers ride comfort directly. The car body panels’ acoustic contribution analysis can determine the location of the panels which affect considerably the interior structural noise. Then that modifying the car body panels with a clear aim can improve the vibration characteristics of car body panels to reduce the interior noise. Using acoustic transfer vector method, the car body panels’ acoustic contribution of the high speed EMU were analyzed to determine the location of the panels which affect considerably the interior noise.