Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach

1995 ◽  
Author(s):  
Hans-Walter Wodtke ◽  
Gary H. Koopmann
Keyword(s):  
Acoustic Radiation ◽  
Sound Intensity ◽  
Structural Vibration ◽  
Acoustic Response ◽  
Radiation Problem ◽  
Volume Velocity ◽  
Intensity Measurements ◽  
Radiated Sound ◽  
The Masses ◽  
Radiated Sound Power

Abstract The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.

A compact active structural acoustic control method for minimizing radiated sound power

2021 ◽  
Vol 263 (3) ◽  
pp. 3396-3406
Author(s):  
Scott Sommerfeldt
Keyword(s):  
Control Method ◽  
Acoustic Radiation ◽  
Structural Vibration ◽  
Sound Power ◽  
Flat Plates ◽  
Spatial Gradients ◽  
Acoustic Control ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Structural Acoustic Control

Active structural acoustic control is an active control method that controls a vibrating structure in a manner that reduces the sound power radiated from the structure. Such methods focus on attenuating some metric that results in attenuated sound power, while not necessarily minimizing the structural vibration. The work reported here outlines the weighted sum of spatial gradients (WSSG) control metric as a method to attenuate structural radiation. The WSSG method utilizes a compact error sensor that is able to measure the acceleration and the acceleration gradients at the sensor location. These vibration signals are combined into the WSSG metric in a manner that is closely related to the radiated sound power, such that minimizing the WSSG also results in a minimization of the sound power. The connection between WSSG and acoustic radiation modes will be highlighted. Computational and experimental results for both flat plates and cylindrical shells will be presented, indicating that the WSSG method can achieve near optimal attenuation of the radiated sound power with a minimum number of sensors.

Application of the Helmholtz Integral in Acoustics

1986 ◽  
Vol 108 (4) ◽  
pp. 447-453 ◽  
Author(s):  
M. A. Latcha ◽  
A. Akay
Keyword(s):  
Acoustic Radiation ◽  
Surface Element ◽  
Sound Power ◽  
Acoustic Response ◽  
Element Size ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Helmholtz Integral

The solution of an isoparametric, overdetermined formulation of the Helmholtz Integral is presented and demonstrated in three examples of acoustic radiation from spherical sources. The placement of the interior, overdetermining points is discussed and guidelines concerning surface element size are developed and tested. The total radiated sound power and transient acoustic response of a dilating sphere are computed.

Acoustic Radiation Simulation of Marine Sliding-Thrust Bearing Shell Based on SYSNOISE

2011 ◽  
Vol 291-294 ◽  
pp. 1961-1964
Author(s):  
Guang Liang Zhao
Keyword(s):  
Dynamic Analysis ◽  
Boundary Element ◽  
Thrust Bearing ◽  
Acoustic Radiation ◽  
Element Model ◽  
Sound Power ◽  
Supporting Structure ◽  
Radiated Sound ◽  
The Impact ◽  
Radiated Sound Power

This paper takes marine Kingsbury sliding thrust bearing as the research object and conducts the finite element dynamic analysis with the aid of ANSYS software. On this basis, the acoustic boundary element model of a sliding thrust bearing shell is established with the ANSYS dynamic analysis results as the boundary excitation conditions. Besides, the radiated sound power of the shell is calculated by indirect boundary element method in SYNOSISE software. The influence of different condition parameters on the radiated sound power of the shell is perceived through the analysis of several rotation-thrust conditions. As for the special structure of this kind of sliding-thrust bearing, this paper states the impact of the supporting structure performance parameters, the pad number and damp of shell on the shell radiated sound power. The optimized measure for the supporting structure and the plan concerning the pad number’s selection lays the theoretical basis for damping and noise-reducing research on marine sliding-thrust bearing and its rotor system.

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.

Investigation of the Physical Mechanism of Walking Noise Radiation of Laminate Floor-Coverings

2005 ◽  
Vol 12 (3) ◽  
pp. 141-163 ◽  
Author(s):  
André Jakob ◽  
Rudi Volz ◽  
Michael Möser
Keyword(s):  
Physical Mechanism ◽  
Near Field ◽  
Sound Radiation ◽  
Sound Intensity ◽  
Structural Vibration ◽  
Single Frequency ◽  
Bending Waves ◽  
Intensity Measurements ◽  
Frequency Maximum ◽  
Floor Coverings

This paper reports on an investigation of the physical mechanism of walking noise radiated by laminate floor coverings with and without backings. In pretests of single laminate panels the influence of different backings on the structural vibration of the panels was determined and material parameters like Young's modulus and bending stiffness were obtained. From these parameters the coincidence frequency could be estimated. The main tests were performed with hard rubber balls falling on laminate floor coverings of different sizes and with different backings. Results show that the radiated sound has a single frequency maximum, which is far below the coincidence frequency. From this and from confirming sound intensity measurements it follows that the sound radiation is a locally constrained phenomenon. Additionally, vibration measurements show that the near field of bending waves dominates the vibration and bending wave propagation can be neglected. The characteristics of the near field vibration and therefore the sound radiation can be controlled by the choice of backing of the laminate floor covering.

ENFORCING RECIPROCITY IN NUMERICAL ANALYSIS OF ACOUSTIC RADIATION MODES AND SOUND POWER EVALUATION

2012 ◽  
Vol 20 (03) ◽  
pp. 1250005 ◽  
Author(s):  
HERWIG PETERS ◽  
NICOLE KESSISSOGLOU ◽  
STEFFEN MARBURG
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Acoustic Radiation ◽  
Sound Power ◽  
Impedance Matrix ◽  
Radiated Sound ◽  
The Asymmetry ◽  
Power Evaluation ◽  
Radiated Sound Power ◽  
Element Method

By identifying the efficiently radiating acoustic radiation modes of a fluid loaded vibrating structure, the storage requirements of the acoustic impedance matrix for calculation of the sound power using the boundary element method can be greatly reduced. In order to compute the acoustic radiation modes, the impedance matrix needs to be symmetric. However, when using the boundary element method, it is often found that the impedance matrix is not symmetric. This paper describes the origin of the asymmetry of the impedance matrix and presents a simple way to generate symmetry. The introduction of additional errors when symmetrizing the impedance matrix must be avoided. An example is used to demonstrate the behavior of the asymmetry and the effect of symmetrization of the impedance matrix on the sound power. The application of the technique presented in this work to compute the radiated sound power of a submerged marine vessel is discussed.

A method to compute the radiated sound power based on mapped acoustic radiation modes

2014 ◽  
Vol 135 (2) ◽  
pp. 679-692 ◽  
Author(s):  
Haijun Wu ◽  
Weikang Jiang ◽  
Yilin Zhang ◽  
Wenbo Lu
Keyword(s):  
Acoustic Radiation ◽  
Sound Power ◽  
Radiated Sound ◽  
Radiated Sound Power

Experimental Characterization of a Car Window Excited by Turbulent Flow Using Scanning Sound Intensity Techniques

2012 ◽  
Author(s):  
Daniel Fernandez Comesaña ◽  
Eduardo Latorre Iglesias ◽  
Malcolm Smith ◽  
Hans-Elias de Bree
Keyword(s):  
Turbulent Flow ◽  
Particle Velocity ◽  
Automotive Industry ◽  
Sound Intensity ◽  
Aerodynamic Noise ◽  
Experimental Characterization ◽  
Velocity Measurements ◽  
Radiated Sound ◽  
Radiated Sound Power

Reducing the aerodynamic noise produced by turbulent flow exciting a car window is one of the current noise control challenges in the automotive industry. Flow separation and later reattachment into a turbulent boundary layer and turbulent wake occur because of flow over the A-pillar and the wing mirror. Experiments have been carried out to represent an idealised wing mirror noise problem using flow over a half cylinder exciting a flat plate. A scanning P-U (pressure-particle velocity) probe was used to measure various aspects of the window response and sound radiation, including the energy distribution of the vibrating surface, the total radiated sound power and hence the radiation efficiency. In addition, experimental results showed that the operational deflection shapes of the car window can be visualized by using scanning particle velocity measurements, obtaining similar results as with step-by-step measurements using a roving accelerometer. The scanning sound intensity maps also proved to be helpful for detecting weaknesses of the initial experimental setup as part of the experimental optimization.

Vibroacoustic Characterization of a New Hybrid Wing-Body Fuselage Concept

2012 ◽  
Author(s):  
Albert Allen ◽  
Adam Przekop
Keyword(s):  
Energy Analysis ◽  
Acoustic Radiation ◽  
Analysis Model ◽  
Energy Correlation ◽  
Model Predictions ◽  
Out Of Plane ◽  
Thin Skin ◽  
Radiated Sound ◽  
Radiated Sound Power

A lighter, more robust airframe design is required to withstand the loading inherent to next generation non–cylindrical commercial airliners. The Pultruded Rod Stitched Efficient Unitized Structure concept, a highly integrated composite design involving a stitched and co-cured substructure, has been developed to meet such requirements. While this structure has been shown to meet the demanding out-of-plane loading requirements of the flat-sided pressurized cabin design, there are concerns that the stiff co-cured details will result in relatively high acoustic radiation efficiencies at frequencies well below the thin skin acoustic coincidence frequency. To address this concern and establish a set of baseline vibroacoustic characteristics, a representative test panel was fabricated and a suite of tests were conducted that involved measurements of panel vibration and radiated sound power during point force and diffuse acoustic field excitations. Experimental results are shown and compared with Finite Element and Statistical Energy Analysis model predictions through the use of modal and energy correlation techniques among others. The behavior of the structure subject to turbulent boundary layer excitation is also numerically examined.

Sound Radiation From a Propeller in a Submerged Rib-Stiffened Duct

2008 ◽  
Author(s):  
Wenlong Zhang ◽  
Hafiz M. Atassi
Keyword(s):  
Dispersion Relation ◽  
Acoustic Radiation ◽  
Strength Distribution ◽  
Acoustic Response ◽  
Dipole Strength ◽  
Compact Source ◽  
Source Effects ◽  
Internal Forces ◽  
Radiated Sound ◽  
Propeller Blades

This paper examines the interaction of nonuniform flows with propeller blades in a submerged elastic duct. The acoustic radiation from the duct is calculated and correlated to the flow nonuniformities and the propeller and duct characteristics. The case of a stiffened duct with ribs is also considered and the dispersion relation of the duct modes is compared with that of a regular duct. The dispersion relation of the stiffened duct has a periodic structure similar to that of connected oscillators with large number of independent modes. Because of our interest in the acoustic radiation of such a system, we focus our attention on the flexure modes. The model is first tested with simple internal forces such as monopoles and dipoles. The results for unstiffened ducts show strong directivity as the dipole radial location moves closer to the duct wall. For stiffened ducts, the magnitude of the acoustic response as well as the directivity vary strongly and show large peaks near the stiffened duct free modes. For a propeller, an Euler code provides the pressure distribution along the blades. This represents the dipole strength distribution. Its radiated sound is calculated by summing up the contribution of the distributed dipoles. In this process, compact source effects are also taken into account.

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