• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.81-86
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• 1996

Some investigations have been made to evaluate the sound quality of a loudspeaker system, objectively and accurately. Also, an algorithm is proposed to predict the various subjective values regarding loudspeaker performance based on the frequency response measured in anechoic chamber. A PC-based software that processes the proposed algorithm has also been developed. To verify the validity of the developed software, three loudspeakers has been evaluated using it and the evaluation results have been compared with the results of the listening test. The comparison between the two showed a good similarity.

• The Journal of the Acoustical Society of Korea
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• v.21 no.4
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• pp.415-420
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• 2002

To identify linear parameters of loudspeaker, two methods are presented. Linear parameter identification methods by box method and added mass method are developed. These methods are compared with conventional software to show advantages and disadvantages of developed methods. Results identified by conventional method of Laud software are significantly different from developed methods. But two methods developed show 4% error in Thiele-Small (TS) parameters identified. In box method, it shows that TS parameters are dependent on the amount of porous material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.153-159
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• 1996

The acoustic characteristics of a direct radiator type loudspeaker has been studied in this paper. The vibration displacement of the speaker cone paper obtained by the finite element analysis has been converted into the vibration velocity and used as a boundary condition for the acoustic analysis. The frequency characteristics and the sound pressure distribution of the loudspeaker resulted from the radiation of the cone vibration have been calculated by the boundary element analysis. The numerical results have been verified by experiments carried out in an anechoic chamber. The variations of the acoustic characteristics due to the changes of some design parameters have been examined using the numerical model.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.764-769
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• 1994

The impedance of an electro-acoustic transducer can be controlled by motional feedback, and the noise in a duct can be reduced actively by adjusting the impedance using an additional sound. In this paper, two approaches for active noise control using motional feedback (MFB) loudspeaker are described. First configuration uses an external sensor to pickup of source directly. In this configuration, the adaptation of controller is necessary to compensate the change of transfer function from noise source to control poing. The second configuration uses a new adaptive algorithm specialized for peridic noise. Because this configuration does not require any reference input and the error sensor couples very tightly with control loudspeaker, this MFB system itself is independent of the duct condition. No microphone are required in both configurations, so that a more reliable and stable active control system can be realized under severe conditions such as high pressure, high temperature, dust, flow and so on.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.68-72
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• 1993

A method to measure the distortions of the loudspeaker at low frequencies without an anechoic chamber is proposed. This method utilizes the fact that the n-th harmonic distortion outside the enclosure is boosted by 40log n dB compared to that inside the enclosure. By compensating for the effect of standing waves occuring inside the enclosure, it is possible to predict the distortions for wide frequency ranges below the first break-up frequency of the diaphragm. The method is applicable to the intermodulation distortion as well.

• The Journal of the Acoustical Society of Korea
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• v.31 no.4
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• pp.214-224
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• 2012

The objective of this paper is to design multichannel spherical loudspeaker array by considering various positioning methods such as Gaussian grid, Lebedev grid and packing method. For the spatial sound manipulation, which is to make desired sound field by controling multiple sound sources, the Kirchhoff- Helmholtz integral states that sound fields can be reproduced in terms of infinite control sources on the integral surface. But since we cannot control infinite number of sources for the implementation, we have to allocate finite number of sound sources which can approximately act as infinite number of sources. To manipulate sound field inside of a sphere (which is typical example of three dimensional array) by controlling sound sources on the surface, three methods of allocating sound sources, which are Gaussian grid, Lebedev grid and packing method, are reviewed. For each geometry, the performances of manipulation rendered by time-reversal operator and higher-order ambisonics are compared.

• Journal of Broadcast Engineering
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• v.20 no.5
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• pp.667-675
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• 2015

As the interest on the high-definition and high-quality broadcasting is increased, the request on the high quality sound signal is enlarged as well as on the video signal's quality. One factor contributing to the high-quality of audio signal is an expansion of reproduction channels like 10.2channel and 22.2channel, but there is a problem of speaker installation issue of these many channels. One solution to solve this problem, we can use frontal loudspeaker array reproduction technique making virtual surround sound. So in this paper, we introduce theocratical analysis on the Wave Field Synthesis used for speaker array based sound reproduction and also present the result about the subjective listening test of reproduction performance based on this technique to check the perfoemance of this system. As a result, we showed WFS based frontal loudspeaker array reproduction method could provide sufficient performance compared to conventional discrete 5.1 channel reproduction method.

• Textile Coloration and Finishing
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• v.29 no.1
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• pp.25-36
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• 2017

This study worked on the synthesis of waterborne polyurethane/epoxy hybrid resins containing aminosilane compound to replace conventional phenol resins used for a coating material for loudspeaker dampers, which are not harmful to human being. Waterborne polyurethane resins were synthesized from two diisocyanate of 4,4'-diphenylethane diisocyanate and toluene diisocyanate, two polyols of polyester polyols(PEP), polycarbonatediol(PCD), including and anionic center of dimethylol butanoic acid, a chain extenders of ethylenediamine(EDA), and a neutral agent of triethylamine. Synthesized polyurethane resins and commercially available bisphenol A type waterborne epoxy resin were blended in weight ratios of 80:20 to prepare polyurethane/epoxy hybrid resins. The synthesized waterborne polyurethane/epoxy hybrid resins were reacted with aminosilane compound to improve mechanical properties. Aminosilane-treated polyurethane /epoxy hybrid resins showed better mechanical properties.

• The Journal of the Acoustical Society of Korea
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• v.26 no.6
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• pp.276-285
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• 2007

In this paper it was discussed and compared measured loudspeaker impedance curve with ones reconstructed by TS parameters estimated using four kinds of parameter estimation methods developed in frequency domain. Frequency dependent parameters were introduced and derived using least square error minimization technique. For known dynamic mass TS parameter estimation methods were reviewed and also proved non-uniqueness of these parameters by simulation method. Minimum phase transformation was adopted to derive phase information from magnitude of loudspeaker electrical impedance curve measured by one channel analyzer.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.325-332
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• 2008

The prediction method of TS parameters, frequency response, and electrical input impedance is proposed with physical properties of parts and results of electromagnetic FEA(Finite Element Analysis) in a loudspeaker driver design. In design for weight reduction and improvement of flux density asymmetry, the prediction results are well coincided with measurement ones. As the applications, it can be applied in design for improvement of the $2^{nd}$ harmonic distortion with flux density distribution analysis. The proposed method is expected to be utilized for reducing trial-and-error process in electromagnetic parts design. It can also be used for providing guidelines for parts selection in the early stages.