Browsing by Author "Chen, Rong-Liang"

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Electroacoustic analysis of an electret loudspeaker using combined finite-element and lumped-parameter models
(2009-06-01)
Bai, Mingsian R.
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Chen, Rong-Liang
;
Wang, Chun-Jen
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機械工程學系
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Department of Mechanical Engineering
An unconventional type of electrostatic loudspeaker is presented in this paper. The loudspeaker made of thin, light, and flexible electret material lends itself well to the space-concerned applications. Electrical impedance measurement reveals that the coupling between the electrical system and the mechanical system is weak, which renders conventional parameter identification based on electrical impedance measurement impractical. A different approach is thus employed to model the electret loudspeaker. To predict the loudspeaker's dynamic response, finite-element analysis (FEA) is conducted on the basis of a simple model and a full model. In the simple model, FEA is applied to model the electret membrane, leaving the rest of system as rigid parts. In the full model, FEA is applied to model the entire membrane-spacer-back plate assembly. Velocity response of the membrane subject to a uniformly distributed force is calculated using FEA harmonic analysis. Mechanical impedance is then calculated with the velocity response. The acoustical impedance due to the back cavity, pores, and the radiation loading at the front side is calculated by theoretical formulas. The volume velocity of the membrane and the resulting on-axis sound pressure level are predicted with electrical-mechanical-acoustical analogous circuits. The response data predicted by the simulation compare very well with experimental measurements. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3117377]
Optimal design of loudspeaker systems based on sequential quadratic programming (SQP)
(2007-01-01)
Bai, Mingsian R.
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Chen, Rong-Liang
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機械工程學系
;
Department of Mechanical Engineering
Miniature loudspeakers are key components to many 3C (computer, communication, and consumer electronics) products, especially for portable devices such as mobile phones, PDAs, and MP3 players. Due to size limitation, miniature loudspeakers suffer from the problem of low output level. To gain higher output, one tends to drive the miniature loudspeaker over the excursion limit and induce nonlinear distortion. Thus how to best reconcile the conflicting requirements of nonlinear distortion and acoustic output is extremely crucial in the design of such loudspeakers. To address the issue, a systematic procedure is presented to pinpoint optimal designs appropriate for miniature dynamic moving-coil loudspeakers. The optimization procedure is based on an electroacoustic model established by using the test-box method. Characteristics including voice-coil impedance, frequency response, and harmonic distortion are evaluated. The results show that significant improvement in output performance and excursion limitation has been gained by using the optimal design.
Optimal design of resonant piezoelectric buzzer from a perspective of vibration-absorber theory
(2007-09-01)
Bai, Mingsian R.
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Chen, Rong-Liang
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Chuang, Chung-Yuan
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Yu, Cheng-Sheng
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Hsieh, Huey-Lin
In this paper, an optimization technique is presented for the design of piezoelectric buzzers. This design technique aims at finding the optimal configuration of the coupled cavity and diaphragm structure to maximize the sound pressure output. Instead of measuring the material constants of the piezoelectric ceramic and the metal diaphragm, an "added-mass method" is developed to estimate the equivalent electromechanical parameters of the system on which an analogous circuit can be established. The electrical impedance and on-axis sound pressure level of the piezoelectric buzzer can be simulated by solving the loop equations of the electromechanoacoustical analogous circuit. An interesting finding of this research is that the nature of the piezoelectric buzzer bears remarkable resemblance to that in the dynamic vibration absorber theory. Much physical insight can be gained by exploiting this resemblance in search of the optimal configuration. According to the system characteristic equation, a design chart was devised to "lock" the critical frequency at which the system delivers the maximal output. On the basis of the analogous circuit and the vibration absorber theory, an optimal design was found with constrained optimization formalism. Experiments were conducted to justify the optimal design. The results showed that the performance was significantly improved using the optimal design over the original design. Design guidelines for the piezoelectric buzzers are summarized. (c) 2007 Acoustical Society of America.
Optimization of Microspeaker Diaphragm Pattern Using Combined Finite Element-Lumped Parameter Models
(2008-08-01)
Bai, Mingsain R.
;
Liu, Ching-Yu
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Chen, Rong-Liang
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機械工程學系
;
Department of Mechanical Engineering
Microspeakers in portable devices are expected to meet a number of conflicting requirements such as miniaturization, high output level, and good sound quality. In contrast to large loudspeakers, the structures of microspeakers are generally simplified by removal of the suspension. The diaphragm serves as not only a sound radiator but also the suspension. Thus, the pattern design of the diaphragm is crucial to the overall response and performance of a microspeaker. The traditional approach for modeling microspeakers using lumped parameter models is generally incapable of modeling flexural modes in high frequencies. In this paper, we present a hybrid approach that combines finite-element analysis (FEA) and electro-mechano-acoustical (EMA) analogous circuit to provide a more accurate model than the conventional approaches. In particular, the minute details of diaphragms are taken into account in calculating the mechanical impedance of the diaphragm-voice coil assembly using FEA. The mechanical impedance is then incorporated into the lumped parameter model. The responses can be simulated by solving the loop equations. On the basis of this simulation model, we optimize the pattern design of the diaphragm using the Taguchi method. In addition, we determine the optimal number of diaphragm corrugations by using sensitivity analysis.
Sound broadcasting mechanism and electronic device using the same
(2008-07-17)
Yu, Wen-Ting
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Bai, Mingsian R.
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Chen, Rong-Liang
A sound broadcasting mechanism and an electronic device using the same are provided. The sound broadcasting mechanism includes a sound box, a sound broadcasting element and a sound enhancing element. The sound broadcasting element is disposed at the surface of the sound box to generate a sound signal. The sound enhancing element is disposed at the surface of the sound box. The sound enhancing element includes a resonating film and a weight increasing element. The resonating film can resonate with the sound signal in a resonating frequency range to enhance the sound intensity of the sound signal in the resonating frequency range. The weight increasing element is attached to the surface of the resonating film. The weight of the weight increasing element is related to the resonating frequency range.
System for producing the parameters of a bass-enhanced loudspeaker enclosure
(2009-08-27)
Bai, Ming-Sian R.
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Zhang, Huan-Sheng
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Chen, Rong-Liang
A system for producing parameters for a bass-enhanced loudspeaker enclosure; meanwhile, a low-frequency extended frequency, a quality and quantity ratio and radius of a port need to be defined for the system. Also, the resonance frequency of a mechanical system and the quality and quantity of a mechanical system are fixed to obtain the parameters for the frequency ratio, the length of the duct and the cavity volume inside the device, etc. and to manufacture the bass-enhanced loudspeaker enclosure.