• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.83-86
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• 2021

In this paper, electric fields in electromagnetic reverberation chambers, which are used as a substitute facility for EM-free anechoic chambers, are analyzed. This paper focused on the 4-5 GHz band, which is expected to adversely affect equipment. To analyze the field uniformity inside the electromagnetic reverberation chamber, electric field strengths are sampled and finite-difference time-domain method was used for numerical analysis. Moreover, Quadratic residue diffuser was used to improve the characteristics of the electromagnetic reverberation chamber and the uniformity of the internal field strength. Standard deviation, tolerance characteristics, and partiality characteristics were compared while varying the aiming point of transmission antenna.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.79-84
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• 2007

This paper presents an improved field uniformity in a reverberation chamber, that can be alternatively used for the analysis and the measurement of electromagnetic interference and immunity, with a designed CRD(Cubical Residue Diffuser) that have various dimensions. The Schroeder type CRD is designed for $1\sim3$ GHz band and the FDTD(Finite Difference Time Domain) method is used to analyze the field characteristics. At 2 GHz, the standard deviation of test volume in the reverberation chamber is the smallest and has a good field distribution with a CRD of $40\sim80%$ dimension of one side of the reverberation chamber. The Electric field uniformity gets worse when the dimension of a CRD is either below 40 % or above 80 % of the side wall. The result shows that the standard deviation of the test volume in the reverberation chamber with a CRD of 44 % dimension is improved by 1 dB compared with that of the reverberation chamber with a CRD of 100 % dimension.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.230-233
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• 2001

Revision of KS, Korean Standards, is currently actively discussed. It is just the time for a new world class standards under the new system with WTO, World Trade Organization. This paper is a part of "Researches on the Standards in the Building Acoustic Field", as one of KS revision projects. The aim of this study is to define the requirements for measuring the reverberation time of rooms with reference to other acoustical parameters. In the former KS, there is no items matched with this purpose. Therefore measuring reverberation time and other room acoustical parameters with confidential test procedure was impossible. On these basis, a new part of KS is proposed, and some problems remained and further discussions in the proposed draft are described in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.786-790
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• 2003

The purpose of this research is to observe that the acoustic characters of classroom have some difference by several conditions. TSP has used to measure impulse response and such physical indexes as RT(Reverberation Time), D$\sub$50/, and STI(Speech-Transmission-Index) are computed by it. we investigate difference under some conditions such as when students were present at each classroom and when was not so, and when professor used a microphone and unused it. In this study, we found that reverberation time when people take a seat is lower than was not so. we wish to help one who work for construction industry, as they build a kind of classroom

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.379-382
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• 2005

Recently, we founded acoustic research laboratory consist of five reverberation rooms on the basis of ISO regulations. Four kinds of experiment are possible in our laboratory such as sound transmission loss of wall, sound attenuation of suspended ceiling, absorption coefficient, reduction of transmitted impact sound by floor coverings. We are going to provide our customers with officially authorized acoustics data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.83-88
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• 2001

The sound absorption coefficient of glass wool (bulk density of 48 kg/m:1 and 32 kg/m7) was measured by reverberation room method as varying their cross-sectional area. The results show that the absorption is larger for smaller samples because of edge effect. The absorption coefficient with two different kinds of sources. 1/.7-octave band and while noise, gives similar values.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.4
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• pp.373-378
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• 2002

This paper presents the results of an electromagnetic field uniformity of a triangular reverberation chamber that can be used alternatively for analysis and measurement of electromagnetic interference and immunity test. Equilateral triangular reverberation chamber and Schroeder diffusers were designed and fabricated for this purpose. FDTD simulation method was applied to analyze the field distribution inside of two different types of reverberation chambers. As a result, the electromagnetic field uniformity was improved inside of triangular reverberation chambers, and the measured field uniformity was improved by 1 ∼4 ㏈ compared to the ones without diffusers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.960-965
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• 2014

Transmission loss of specimen is calculated by measuring energy of incident and transmission and using reverberant room of large size. But normal measurement of transmission loss has trouble because it is actually demanded that large area and specimen of certain size is satisfied with condition of diffused sound field. Especially, in case of mechanical component, interested frequency band is mid-frequency band between 500 ~ 2k Hz, and it is used to be available to minimize a reverberation chamber under conditions satisfying acoustic one because production of specimen for transmission loss measurement has limit. But, as in semi-reverberation room, it is difficult to satisfy condition of diffuse sound field and modification factor is applied to complement that. Correction factor when measuring transmission loss using semi-reverberation chamber is required accuracy because it works as main factor determining reliability of reuslts on transmission loss. In this study, it is analyzed that an effect on correction factor based on varying materials and sizes of specimens in order to deduction of it. Also It is confirmed that applied by elicited correction factor with actual railway vehicle's floor has reliability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.880-884
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• 2014

RT (reverberation time) of outdoor spaces surrounded by multi-storey buildings depends on many designable factors such as the openness, volume and building layouts, etc. This study therefore aims to clarify the influential factors for RT in outdoor spaces surrounded by buildings with complicated topographical conditions. A series of measurements were carried out for 15 outdoor spaces in 6 apartment complexes with different building layouts. An Empirical method considering the openness, averaged ray length and building high is also suggested, to predict RT approximately in the outdoor spaces. The overall results suggest that RT in outdoor spaces of apartment complexes is significantly influenced by source-receiver distance and building layouts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.686-689
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• 2005

This study aims to analyzed the acoustics characteristics of Korean Traditional Houses in Chonnam Province varied with lay out and floor plane to reflect the way of control for environmental condition. These houses are surveyed the reverberation time and level difference between rooms of the main living room and other main floored room, master room and kitchen. As a result, the reverberation time of traditional rooms are below 0.6 second, and the sound insulation performance of Korean traditional door are mostly very low grade with D-15. The level difference between rooms are low grade not to meet minimum class except between main living room and master room away from main living building.