A New Design Strategy for Minimizing Sound Radiation of Vibrating Beam Using Dimples

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
W. N. Cheng ◽  
C. C. Cheng ◽  
G. H. Koopmann
Keyword(s):  
Vibration Mode ◽  
Sound Radiation ◽  
Design Strategy ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Optimization Scheme ◽  
Modal Assurance Criterion ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Radiated Sound Power

A method is proposed for minimizing the sound radiation of a vibrating beam by patterning the beam with a series of cylindrical dimples such that one or more of the vibration modes have the same shape as the corresponding weak modes. In implementing the proposed approach, the objective is to minimize the shape difference between the vibration mode(s) and the designated weak mode(s) rather than to minimize the radiated sound power at a specific frequency or over a certain bandwidth. The design objective is achieved by calculating the weak modes of the beam using the finite element method and then applying an optimization scheme with the modal assurance criterion (MAC) as the objective function. The optimization results, which cause the vibration mode(s) of the dimpled beam to approach the corresponding weak modes(s), determine the dimple angle and dimple depth. The numerical results show that the radiation efficiency of the optimized dimpled beam using MAC as the objective is generally lower than that of a uniform beam. However, the effectiveness of the proposed design strategy depends on the degree of closeness between the shape of the vibration mode(s) of the dimpled beam and that of the designated weak mode(s).

Weak Radiator Design Using Dimples

2010 ◽  
Author(s):  
Wen Nan Cheng ◽  
Chih Chun Cheng ◽  
Gary H. Koopmann
Keyword(s):  
Vibration Mode ◽  
Design Method ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Key Issues ◽  
Beam Surface ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Do So

A design method for achieving minimum sound radiation from a beam is presented. The strategy is to form a series of cylindrical dimples on the beam surface in order to make one or more vibration modes of this dimpled beam have the same shape as the weak modes. Consequently, the dimpled beam behaves as a weak radiator when one or more vibration modes are excited. Instead of minimizing the radiated sound power at a specific frequency or in a bandwidth, the objective is to maximize the modal assurance coefficient (MAC) which quantifies resemblance between the vibration mode of a dimpled beam and a weak mode. To perform this strategy, two key issues are addressed in this paper. The first is to determine the so-called weak mode of a beam. And the second is how to determine the required dimple size and the dimple location on this beam so that the dimpled beam may have vibration modes resembled to the weak modes. A methodology to do so based on the finite element method and the mode assurance criteria is proposed. Results show that the radiation efficiency of the dimpled beam after optimization using MAC as the objective is generally lower than the uniform beam. However, the effectiveness of this strategy depends on how close in shape between the vibration mode of the dimpled beam and the designated weak mode.

Vibroacoustic Optimization of Mechanical Structures: A Controlled Random Search Approach

2012 ◽  
Vol 622-623 ◽  
pp. 158-161 ◽  
Author(s):  
Mostafa Ranjbar ◽  
Steffen Marburg
Keyword(s):  
Random Search ◽  
Power Level ◽  
Search Method ◽  
Frequency Range ◽  
Controlled Random Search ◽  
Sound Power Level ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Search Approach ◽  
Radiated Sound Power

A combination of controlled random search method and geometry modification concept is used to minimize the root mean square level of structure borne sound for a model. The structure is a rectangular plate made of steel. A specific frequency range for this porpuse is considered. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure within a limited time.

Genetic Algorithms for the Vibroacoustic Optimization of the Thin Parts of I.C. Engine

2003 ◽  
Author(s):  
Xiaolong Deng ◽  
Zongjie Zhang ◽  
Chunpeng Sun ◽  
Shaohe Li
Keyword(s):  
Noise Level ◽  
Numerical Optimization ◽  
Acoustic Power ◽  
Single Frequency ◽  
Acoustic Response ◽  
Promising Tool ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Noise Vibration ◽  
Radiated Sound Power

The Noise Vibration Harshness (NVH) behavior of engines is one of the predominant factors for market acceptance of vehicles. To reach this goal it is necessary to reduce the absolute noise level and also the noise level in specific frequency ranges. The design of radiating structures for minimal sound radiation is a multidisciplinary problem that involves complex objective functions and expensive computations. In this paper, genetic algorithm is used as a promising tool for numerical optimization of such problems. The objective of the study is to determine effective, general design methods for determining the optimal design of thin parts of I.C. engine that minimizes the total radiated acoustic power. Variable attached discrete masses are considered. Acoustic response is minimized either at a single frequency or first five natural frequencies. Radiated sound power is calculated using a boundary element method, in conjunction with a finite element solver ANSYS for the solution of the structural acoustical problem.

Relation Between Structural Intensity-Based Scalars and Sound Radiation Using the Example of Plate-Rib Models

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Clarissa Schaal ◽  
Johannes Ebert ◽  
Joachim Bös ◽  
Tobias Melz
Keyword(s):  
Objective Function ◽  
Energy Flow ◽  
Vibrational Energy ◽  
Sound Radiation ◽  
Specific Region ◽  
Sound Power ◽  
Structural Intensity ◽  
Radiated Sound ◽  
Very High ◽  
Radiated Sound Power

The ability of the structural intensity (STI) to predict changes in the sound radiation of structures due to geometric modifications is investigated using the academic example of plate-rib models. All models consist of the same plate and are modified by attaching a rib, whose position, orientation, and length are varied. Various scalar quantities are derived from the STI and quantitatively compared to the equivalent radiated sound power (ERP) for each model. Based on this comparison the relation between the STI-based scalars and the ERP is studied to determine an STI-based scalar that can serve as the objective function for numerical structural optimizations. The influence of the rib parameters on the most promising STI-based scalar is analyzed by means of a variance-based sensitivity analysis. The STI pattern of those models with very high and very low ERP values are additionally analyzed to describe the characteristics of STI. The results of this study indicate that the STI pattern of models with low ERP has paths and vortices that can be more clearly identified compared to those in models with high ERP. The angular orientation of the rib has by far the highest influence on changes in STI and ERP. The results reveal a correlation between the energy flow into a specific region of a structure, an STI-based scalar, and the ERP. Therefore, the vibrational energy flow can indeed serve as an objective function for numerical structural optimizations aiming at reducing the sound radiation.

Sound Radiation Response of a Rectangular Plate Having a Side Crack of Arbitrary Length, Orientation, and Position

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Tanmoy Bose ◽  
Amiya R. Mohanty
Keyword(s):  
Rectangular Plate ◽  
Ritz Method ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Sound Power ◽  
Cracked Plate ◽  
Side Crack ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Here, sound radiation characteristics of a rectangular plate having a side crack of different crack lengths, orientations, and positions are studied considering clamped boundary conditions. First, a free and forced vibration response analysis of a cracked plate is done using the Ritz method. Orthogonal polynomials are used for faster convergence and some corner functions are used to generate the effect of a crack. Radiated sound power and radiation efficiency of the cracked plate are computed by the quadruple integration. A convergence test of radiation efficiency is carried out to fix the number of polynomials and corner functions in the analysis. It is found that the radiation efficiency and radiated sound power computed by the Ritz method are close to the same obtained from the boundary element method (BEM). The natural frequencies computed using the Ritz method are also found to be close to that obtained from the finite element method (FEM). The radiation efficiency curves of different modes are shown for a change in crack length, orientation and position. Finally, the variations of normalized sound power are shown to be due to a change in the crack parameters.

scholarly journals Sound Radiation Characteristics of a Rectangular Duct with Flexible Walls

2016 ◽  
Vol 2016 ◽  
pp. 1-15
Author(s):  
Praveena Raviprolu ◽  
Nagaraja Jade ◽  
Venkatesham Balide
Keyword(s):  
Analytical Model ◽  
Power Level ◽  
Sound Radiation ◽  
Rectangular Duct ◽  
Radiation Characteristics ◽  
Vibration Displacement ◽  
Flexible Walls ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Acoustic breakout noise is predominant in flexible rectangular ducts. The study of the sound radiated from the thin flexible rectangular duct walls helps in understanding breakout noise. The current paper describes an analytical model, to predict the sound radiation characteristics like total radiated sound power level, modal radiation efficiency, and directivity of the radiated sound from the duct walls. The analytical model is developed based on an equivalent plate model of the rectangular duct. This model has considered the coupled and uncoupled behaviour of both acoustic and structural subsystems. The proposed analytical model results are validated using finite element method (FEM) and boundary element method (BEM). Duct acoustic and structural modes are analysed to understand the sound radiation behaviour of a duct and its equivalence with monopole and dipole sources. The most efficient radiating modes are identified by vibration displacement of the duct walls and for these the radiation efficiencies have been calculated. The calculated modal radiation efficiencies of a duct compared to a simple rectangular plate indicate similar radiation characteristics.

scholarly journals Modal Analysis of Laminated “CAS” and “CUS” Box-Beams

2017 ◽  
Vol 64 (4) ◽  
pp. 441-454 ◽  
Author(s):  
Jarosław Gawryluk ◽  
Marcin Bocheński ◽  
Andrzej Teter
Keyword(s):  
Modal Analysis ◽  
Mode Coupling ◽  
Composite Structures ◽  
Vibration Mode ◽  
Coupling Effect ◽  
Experimental Modal Analysis ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Numerical Studies ◽  
Box Beams

Abstract In the paper, the authors discuss the numerical and experimental modal analysis of the cantilever thin-walled beams made of a carbon-epoxy laminate. Two types of beams were considered: circumferentially asymmetric stiffness (i.e., CAS) and circumferentially uniform stiffness (i.e., CUS) beams. The layer-up configurations of the laminate were chosen to get a vibration mode coupling effect in both analysed cases. The aim of the paper was to perform the numerical and experimental modal analysis of the composite structures, when a flapwise bending with torsion coupling effect or flapwise-chordwise bending coupling effect took place. Firstly, numerical studies by the finite element method was performed. The numerical simulations were carried out by the Lanczos method in the Abaqus software package. The natural frequencies and the corresponding free vibration modes were determined. Next, the experimental modal analyses of the CAS and CUS beams were performed. The test stand was consisted of a special grip, two beams with an adhered holder, the LMS Scadas III system with a modal hammer and an acceleration sensor. Finally, the results of both methods were compared.

scholarly journals Faster Calculation of the Low-Frequency Radiated Sound Power of Underwater Slender Cylindrical Shells

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Rui Tang ◽  
He Tian ◽  
Dajing Shang
Keyword(s):  
Cylindrical Shell ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Calculation Process ◽  
Radiated Sound ◽  
Stiffened Cylindrical Shells ◽  
Radiated Sound Power

Based on the fact that beam-type modes play the main role in determining the sound radiation from an underwater thin slender (length-to-radius ratio L/a>20) elastic cylindrical shell, an equivalent-beam method is proposed for calculating the low-frequency radiated sound power of underwater thin slender unstiffened and stiffened cylindrical shells. The natural bending frequencies of the cylindrical shell are calculated by analytical and numerical methods and used to solve equivalent Young’s modulus of the equivalent beam. This approach simplifies the vibration problem of the three-dimensional cylindrical shell into that of a two-dimensional beam, which can be used to simplify the calculation process of radiated sound power. Added mass is used to approximate the fluid-structure coupling, further simplifying the calculation process. Calculation examples of underwater simply supported unstiffened and stiffened cylindrical shells verify the proposed method by comparison with analytical and numerical results. Finally, the effects of the size and spacing of the stiffeners on the sound radiation characteristics of underwater free-free stiffened cylindrical shells are discussed. The proposed method can be extended to the rapid calculation of the sound radiation characteristics of underwater slender complex cylindrical shells in the low-frequency range.

Study on the application and optimization of trichiral raft in a floating raft system

2015 ◽  
Vol 230 (11) ◽  
pp. 1819-1829 ◽  
Author(s):  
Shiyin Xu ◽  
Xiuchang Huang ◽  
Zhipeng Du ◽  
Hongxing Hua
Keyword(s):  
High Frequency ◽  
Stop Band ◽  
Optimization Method ◽  
Hybrid Structure ◽  
Sound Power ◽  
Optimization Scheme ◽  
Floating Raft ◽  
Radiated Sound ◽  
Isolation Performance ◽  
Radiated Sound Power

In this paper, periodic and hybrid trichiral structure is developed as the raft in a floating raft system to enhance isolation performance in the medium and high-frequency range. Firstly, wave propagation in the periodic trichiral structure is analyzed through Bloch theorem. Further study of the hybrid trichiral structure, consisting of multilayer of cells with different geometry, demonstrates that the stop band of this assembly is the superposition of the band gap generated by individual cells. This feature can be used to extend the stop band without affecting the performance in other frequencies. Vibration transmission of the floating raft system is studied through frequency response function based substructuring method. Numerical examples indicate that the sound power radiated from the foundation can be greatly attenuated in the stop band of the periodic trichiral raft. Based on the feature of hybrid structure, an optimization scheme with respect to the trichiral raft is developed with the aim of minimizing the radiated sound power of the system. The proposed modeling and optimization method can be extended to design other regular raft structures with great flexibility.

Shaping acoustic radiation induced by vibrotactile rendering on a touch surface

2021 ◽  
Vol 263 (2) ◽  
pp. 4322-4328
Author(s):  
Sangwon Park ◽  
Wheejae Kim ◽  
Dongjoon Kim ◽  
No-Cheol Park
Keyword(s):  
Acoustic Radiation ◽  
Sound Radiation ◽  
Vibrotactile Feedback ◽  
Acrylic Plate ◽  
Vibration Responses ◽  
Radiation Induced ◽  
Measured Frequency Response ◽  
Radiated Sound ◽  
The Relationship ◽  
Radiated Sound Power

Many electronic devices with touch-sensitive surfaces aim to provide vibrotactile feedback, along with visual or auditory feedback, to facilitate the interaction between the user and the interface. In parallel to these efforts, recent studies developed various vibration rendering techniques, enabling more complex vibration patterns to be generated on the touch surface. However, few have addressed sound radiation induced by vibrotactile rendering on a touch surface, which could significantly impact the haptic interaction's overall perception. This study presents a method to shape the acoustic radiation due to rendering high-fidelity vibrotactile feedback on a touch surface. The proposed method utilizes measured frequency response functions and a vibroacoustic representation of the touch surface to define the relationship between actuator driving signals, vibration responses on the touch surface, and radiated sound power. Proper actuator driving signals are derived from the optimization problem formulated using the relationship. The proposed method was demonstrated through vibration rendering experiments on a touch surface comprising an acrylic plate and voice coil actuators. The results showed that the proposed method could shape the acoustic radiation while rendering target vibration patterns at desired positions on the touch surface. This study's proposed method could allow haptic engineers to design vibrotactile feedback and sound radiation simultaneously for a more compelling haptic experience.

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