scholarly journals The Effect of Plate Discretization on Accuracy of the Sound Radiation Efficiency Measurements

2015 ◽  
Vol 39 (4) ◽  
pp. 511-518 ◽  
Author(s):  
Karolina Kolber ◽  
Anna Snakowska ◽  
Michał Kozupa
Keyword(s):  
Measurement Techniques ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Sound Radiation ◽  
Technical Aspect ◽  
Radiation Efficiency ◽  
Vibration Velocity ◽  
Optimum Level ◽  
Velocity Amplitude ◽  
Sound Radiation Efficiency

Abstract This paper deals with the problem of the effect of discretization level and certain other parameters characterizing the measurement setup on accuracy of the process of determination of the sound radiation efficiency by means of the Discrete Calculation Method (DCM) described by Hashimoto (2001). The idea behind DCM consists in virtual division of an examined sound radiating structure into rectangular elements each of which is further assumed to contribute to the total radiation effect in the same way as a rigid circular piston having the surface area equal to this of the corresponding virtual element and vibrating in an infinite rigid baffle. The advantage of the method over conventional sound radiation efficiency measurement techniques consists in the fact that instead of acoustic pressure values, source (plate) vibration velocity amplitude values are measured in a selected number of regularly distributed points. In many cases, this allows to determine the sound radiation efficiency with sufficient accuracy, especially for the low frequency regime. The key part of the paper is an analysis of the effect of discretization level (i.e. the choice of the number of points at which vibration amplitude measurements are to be taken with the use of accelerometers) on results obtained with the use of the method and their accuracy. The problem of determining an optimum level of discretization for given excitation frequency range is a very important issue as the labor intensity (time-consuming aspect) of the method is one of its main flaws. As far as the technical aspect of the method is concerned, two different geometrical configurations of the measurement setup were tested.

scholarly journals Prediction of Sound Radiation from Submerged Cylindrical Shell Based on Dominant Modes

2020 ◽  
Vol 10 (9) ◽  
pp. 3073 ◽  
Author(s):  
Chao Zhang ◽  
Sihui Li ◽  
Dejiang Shang ◽  
Yuyuan Han ◽  
Yuyang Shang
Keyword(s):  
Cylindrical Shell ◽  
Radiation Power ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Frequency Sound ◽  
Comparison Results ◽  
Sound Radiation Efficiency ◽  
Sound Radiation Power

A sound radiation calculation method by using dominant modes is proposed to predict the sound radiation from a cylindrical shell. This method can provide an effective way to quickly predict the sound radiation of the structure by using as few displacement monitoring points as possible on the structure surface. In this paper, modal analyses of a submerged cylindrical shell are carried out by taking the vibration mode of a cylindrical shell in a vacuum, as a set of orthogonal bases. The modal sound radiation efficiency and modal contributions to sound radiation power are presented, and comparison results show that a few modes dominantly contribute to the sound radiation power at low frequencies. These modes, called dominantly radiated structural modes in this paper, are applied to predict the sound radiation power of submerged cylindrical shells by obtaining the modal participant coefficients and sound radiation efficiency of these dominant modes. Aside from the orthogonal decomposition method, a method of solving displacement modal superposition equations is proposed to extract the modal participant coefficients, because few modes contribute to the vibration displacement near the resonant frequencies. Some simulations of cylindrical shells with different boundaries are conducted, and the number of measuring points required are examined. Results show that this method, based on dominant modes, can well predict the low-frequency sound radiation power of submerged cylindrical shells. In addition, compared with the boundary element method, this method can better reduce the number of required measuring points significantly. The data of these important modes can be saved, which can help to predict the low-frequency sound radiation of the same structure faster in the future.

scholarly journals A Comparison of Vibroacoustic Response of Isotropic Plate with Attached Discrete Patches and Point Masses Having Different Thickness Variation with Different Taper Ratios

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Bipin Kumar ◽  
Vinayak Ranjan ◽  
Mohammad Sikandar Azam ◽  
Piyush Pratap Singh ◽  
Pawan Mishra ◽  
...  
Keyword(s):  
Power Level ◽  
Low Frequency ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Thickness Variation ◽  
Sound Power ◽  
Sound Power Level ◽  
Radiation Behavior ◽  
Thickness Variations ◽  
Different Thickness

A comparison of sound radiation behavior of plate in air medium with attached discrete patches/point masses having different thickness variations with different taper ratio of 0.3, 0.6, and 0.9 is analysed. Finite element method is used to find the vibration characteristics while Rayleigh integral is used to predict the sound radiation characteristics. Minimum peak sound power level obtained is at a taper ratio of 0.6 with parabolic increasing-decreasing thickness variation for plate with four discrete patches. At higher taper ratio, linearly increasing-decreasing thickness variation is another alternative for minimum peak sound power level suppression with discrete patches. It is found that, in low frequency range, average radiation efficiency remains almost the same, but near first peak, four patches or four point masses cause increase in average radiation efficiency; that is, redistribution of point masses/patches does have effect on average radiation efficiency at a given taper ratio.

Characteristics of Modal Sound Radiation of Finite Cylindrical Shells

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Tian Ran Lin ◽  
Chris Mechefske ◽  
Peter O’Shea
Keyword(s):  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Radiation Efficiency ◽  
Boundary Element Methods ◽  
Frequency Range ◽  
Nodal Lines ◽  
Infinite Cylindrical Shell ◽  
Modal Index

Characteristics of modal sound radiation of finite cylindrical shells are studied using finite element and boundary element methods in this paper. In the low frequency range, modal radiation efficiencies of finite cylindrical shells are found to asymptotically approach those of the corresponding infinite cylindrical shell when structural trace wavelengths of the cylindrical shells are greater than the acoustic wavelength. Modal radiation efficiencies for each group of modes having the same circumferential modal index decrease as the axial modal index increases. They converge to each other when the axial trace wavelength is much greater than the circumferential trace wavelength. The mechanism leading to lower radiation efficiency of modes with higher circumferential modal index of short cylinders is explained. Similar to those of flat plate panels, change in slope or waviness is observed in modal radiation efficiency curves of modes with higher order axial modal index at medium frequencies. This is attributed to the interference of sound radiated by neighboring vibrating cells when the distance between nodal lines of a vibrating mode is in the same order or smaller than the acoustic wavelength. The effects of the internal sound field on modal radiation efficiencies of a finite open-end cylinder are discussed.

Acoustoelastic-Based Stress Measurement Utilizing Low-Frequency Flexural Waves

2017 ◽  
Author(s):  
Mohammad I. Albakri ◽  
Vijaya V. N. Sriram Malladi ◽  
Pablo A. Tarazaga
Keyword(s):  
Stress Measurement ◽  
Measurement Techniques ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Lower Sensitivity ◽  
Flexural Waves ◽  
Dispersive Waves ◽  
High Frequencies ◽  
Geometric Uncertainties ◽  
The Cost

Current acoustoelastic-based stress measurement techniques operate at the high-frequency, weakly-dispersive portions of the dispersion curves. The weak dispersive effects at such high frequencies allow the utilization of time-of-flight measurements to quantify the effects of stress on wave speed. However, this comes at the cost of lower sensitivity to the state-of-stress of the structure, and hence calibration at a known stress state is required to compensate for material and geometric uncertainties in the structure under test. In this work, the strongly-dispersive, highly stress-sensitive, low-frequency flexural waves are utilized for stress measurement in structural components. A new model-based technique is developed for this purpose, where the acoustoelastic theory is integrated into a numerical optimization algorithm to analyze dispersive waves propagating along the structure under test. The developed technique is found to be robust against material and geometric uncertainties. In the absence of calibration experiments, the robustness of this technique is inversely proportional to the excitation frequency. The capabilities of the developed technique are experimentally demonstrated on a long rectangular beam, where reference-free, un-calibrated stress measurements are successfully conducted.

Semi-Active Optimization of 2D Wave’s Dispersion Into Shunted Piezocomposite Systems for Controlling Acoustic Interaction

2011 ◽  
Author(s):  
Manuel Collet ◽  
Morvan Ouisse ◽  
Mohammed Ichchou ◽  
Roger Ohayon
Keyword(s):  
Brillouin Zone ◽  
Power Flow ◽  
Electrical Impedance ◽  
Sound Radiation ◽  
Numerical Approach ◽  
Radiation Efficiency ◽  
Bloch Theorem ◽  
Acoustic Interaction ◽  
Energy Diffusion ◽  
Sound Radiation Efficiency

In this paper, we present an application of the Floquet-Bloch theorem in the context of electrodynamics for vibroacoustic power flow optimization by mean of distributed and shunted piezoelectric patches. The main purpose of this work is first to propose a dedicated numerical approach able to compute the multi-modal wave dispersions curves into the whole first Brillouin zone for periodically distributed 2D shunted piezomechanical systems. By using two specific indicators evaluating the evanescent part of Bloch’s waves and the induced electronic damping, we optimize the piezoelectric shunting electrical impedance for controlling energy diffusion into the proposed semi-active distributed set of cells. Sound radiation efficiency is also analyzed for showing the effects of such smart metamaterial for controlling acoustical noise.

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