Browsing by Author "Jiang, C. H."

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Optimal design of rectangular composite flat-panel sound radiators considering excitation location
(2014-02-01)
Jiang, C. H.
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Chang, Y. H.
;
Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
The optimal excitation locations of rectangular composite sound radiation plates to produce relatively smooth sound level pressure (SPL) curves are determined using an optimal design method. In the optimal design process, the vibration of the plate is analyzed using the Rayleigh-Ritz method, the sound pressure produced by the plate is calculated using the first Rayleigh integral, and the optimal excitation location is determined using a global optimization technique. The experimental SPL curves of several sound radiators were measured to verify the accuracy of the theoretical predictions. In the determination of the optimal excitation location, the trial radius of the circular excitation force is used in the vibro-acoustic analysis to predict the theoretical SPL curve of the plate, a SPL discrepancy function is established to measure the sum of the squared differences between the SPLs at the chosen excitation frequencies and the average value of such SPLs, and a global minimization technique is used to search for the best estimate of the radius of the circular excitation force by making the SPL discrepancy function a global minimum. The optimal excitation locations of several composite sound radiators with different aspect ratios and layups are determined using the proposed method. (C) 2013 Elsevier Ltd. All rights reserved.
Sound radiation of panel-form loudspeaker using flat voice coil for excitation
(2017-01-15)
Jiang, C. H.
;
Kam, T. Y.
;
Chang, Y. H.
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機械工程學系
;
Department of Mechanical Engineering
A novel panel-form loudspeaker in which the panel of the speaker is excited by the forces generated through the flat voice coil of a rectangular electro-magnetic type exciter for sound radiation is presented. The exciter when properly designed has the advantage of exerting appropriate loads to the panel so that the major sound pressure level (SPL) dips of the speaker can be suppressed or even eliminated. For designing such panel-form speaker, a method formulated on the basis of the classical plate theory (CPT), Ritz method, and first Rayleigh integral is proposed for predicting the SPL curve of the speaker. An experimental investigation was performed to verify the feasibility of the proposed method. The effects of some system parameters on the major SPL dips of the proposed panel-form speakers are investigated by means of several numerical examples. The optimal locations of flat voice coils for exciting several panel-form speakers are determined to illustrate the important role of excitation location for enhancing sound quality of such speakers via the removal or suppression of the major SPL dips. (C) 2016 Elsevier Ltd. All rights reserved.
Vibration analysis of elastically restrained laminated composite sound radiation plates via a finite element approach
(2013)
Jiang, C. H.
;
Kam, T. Y.
;
機械工程學系
;
Department of Mechanical Engineering
The vibration characteristics (natural frequencies and vibration shapes) of elastically restrained laminated composite plates used for sound radiation are studied via both theoretical and experimental approaches. The laminated composite sound radiation plates restrained by peripheral and/or interior elastic supports are excited using an electro-magnetic exciter for generating sounds. In the theoretical study, a finite element formulation is presented to model the free and forced vibrations of the elastically restrained laminated composite plate. The present finite element method is then used to study the effects of support conditions, plate aspect ratio, and size ratio of plate length to voice coil radius on the vibration characteristics of the elastically restrained laminated composite sound radiation plates. In the experimental study, several centrally restrained laminated composite plates were subjected to sweep sine excitation to determine the frequency response spectra from which the natural frequencies of the plates were identified. The elastically restrained laminated composite plates with salt powder distributed on their top surfaces were excited to generate the vibration shapes of the plates at several selected frequencies. The experimental results are then used to verify the feasibility and accuracy of the proposed finite element model. The close agreement between the experimental and theoretical results has validated the suitability of the proposed finite element model for vibration analysis of sound radiation plates. The theoretical and experimental results presented in this paper can also serve as benchmarks for verifying the correctness of any analytical model established for vibration analysis of laminated composite sound radiation plates. (C) 2013 The Authors. Published by Elsevier Ltd.
Vibro-acoustic formulation of elastically restrained shear deformable stiffened rectangular plate
(2012-11-01)
Kam, T. Y.
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Jiang, C. H.
;
Lee, B. Y.
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機械工程學系
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Department of Mechanical Engineering
A method constructed on the basis of the Rayleigh-Ritz method and the first Rayleigh integral is presented for the vibro-acoustic analysis of elastically restrained shear deformable stiffened rectangular orthotropic plates. In the proposed method, the displacement fields of the plate and stiffeners are formulated on the basis of the first-order shear deformation theory. The theoretical sound pressure level (SPL) curve of the plate is constructed using the responses at different excitation frequencies and the first Rayleigh integral. The experimental SPL curve of an elastically restrained stiffened orthotropic plate was measured to verify the accuracy of the theoretical SPL curve of the plate. The effects of Young's modulus ratio E-1/E-2 on the sound radiation characteristics of elastically restrained stiffened orthotropic plate with different aspect ratios are studied using the proposed method. It has been shown that the effects of Young's modulus ratio become more prominent as the plate aspect ratio gets larger. (C) 2012 Elsevier Ltd. All rights reserved.