• Title/Summary/Keyword: Diffuse Sound Field

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Development of a Simplified Test Apparatus for Measuring Sound Transmission Loss (간이 차음시험장치 개발)

  • 이해성;전오성;강현주;김봉기
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.892-897
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    • 2003
  • This study deals with the performance of a simplified test apparatus for measurement of sound insulation of panels. In order to investigate its performance, results from experiment and theory of the sound transmission loss for single and double panels are compared. Comparative results show that in evaluation of the sound insulation performance, the test apparatus has a cumbersome problem at the low frequency region, i.e. below 315 ㎐, presumably because of the poor diffuse sound field in the chambers. Meanwhile at the high frequency, it shows a considerable results comparable to the theoretical prediction. One of the objective of this study that compares measured results between a real reverberation chamber and a simplified test apparatus, by using a specimen of a sandwich panel. It shows qualitatively resonable agreement from which one can find a potential to provide a design tool.

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A Study on the Improvement of Reverberation Room's Performance (잔향실 성능 검증 및 향상 연구)

  • Kim, Sung-Hoon;Joo, Won-Ho;Kim, Dong-Hae;Bae, Jong-Guk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.171-175
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    • 2006
  • Recently, two reverberation rooms were built up of 300mm thick concrete walls in non-parallel pentagonal shape to measure the sound absorption, transmission, radiation, and impact insulation of acoustical materials, panels, doors, etc. Various acoustic tests, including the sound transmission test, were carried out to investigate their acoustic performances. In order to improve the performance, several modifications on these acoustical parameters, such as the acoustic mode, the position of specimen, the formation of diffuse field, the location of sound source, and flanking transmission, have been conducted. Through a series of tests, the reverberation rooms have been effectively improved so that it could perform a variety of acoustic tests with the international standard. And then, it is expected to be very helpful in developing the low noise design technology for ships.

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An Experimental Study on the Reduction Effect of Reflected Sound and Diffraction Effect by Types of Noise Barrier (방음벽 종류별 반사음 저감효과 및 회절효과에 관한 실험적 연구)

  • 김흥식
    • Journal of KSNVE
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    • v.6 no.2
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    • pp.245-251
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    • 1996
  • This study is to suggest the improved noise barrier which is harmonized with surrounding landscape and maintained the similar reduction of reflected sound and diffraction effects in comparison with the aluminum noise barrier of absorbing type which is formed a great majority in Korea. In this study the two improved models of noise barrier(Diffuse and Disperse type) were designed and compared with the noise barriers of absorbing type in the acoustics performance (the reduction of reflected sound and diffraction effects) through the field and full-scale experimental measurement. As these two models have the same acoustic performance as the noise barrier of aluminum absorbing type, it is suggested that these models can be applied to the improved noise barrier as an alteration of aluminum absorbing type barrier.

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Development of Automated Program for Noise Prediction in Shipboard Compartments (선내 격실 소음 추정 자동화 프로그램 개발)

  • Oh, Young-Keun;Park, Keun-Hyo;Ryu, Seong-Sun;Kang, Tae-Wook;Lee, Dong-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.519-524
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    • 2011
  • The aim of this study is to develop an automated program for noise prediction in shipboard compartments, for this purpose of calculating noise levels accurately and quickly. The program calculates sound power level at HVAC components based on the empirical method suggested by NEBB and utilizing the manufacturer's test data. The program developed uses the GUI functions to help in efficient modeling and calculation. To verify the reliability of developed program, the predicted data was compared with the measured data in shipboard compartments. As a result, the average difference between predicted and measured data is ${\pm}3dB$.

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Development of Cabin Noise Prediction Program Induced by HVAC System (공조시스템 유기 격실 소음 예측 프로그램 개발)

  • Kim, Byung-Hee;Kwon, Jong-Hyun;Cho, Dae-Seung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.554-558
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    • 2004
  • In this paper, we introduce noise prediction program of HVAC system to assist low-noisy design of ship's cabin. The developed program calculates sound power levels at HVAC components considering primary and secondary noise generated by fan and duct element, duct element noise attenuation, and duct break-in noise based on the authentic empirical method suggested by NEBB and acoustic power balancing method. Sound pressure level at cabin with or without ceiling system is evaluated by the diffuse-field theory considering diffuser and duct break-out sound powers. Moreover, the program provides intuitive pre- and post-processors using modem GUI functions to help efficient modeling and evaluation of cabin and HVAC component noise. To validate the accuracy and convenience of the program, noise prediction for a HVAC system is demonstrated.

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Acoustic characteristics of sound field in partially opened rooms - Emphasis on horizontal coupling of diffuse and non-diffuse field - (실내공간의 부분적 개방에 따른 음향특성변화 I - 확산음장과 자유음장의 수평적 결합을 중심으로 -)

  • Jeong, Dae-Up;Choi, Young-Ji;Kim, Ji-Young;Oh, Yang-Ki;Choi, Seok-Ju
    • Journal of Korean Association for Spatial Structures
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    • v.7 no.2 s.24
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    • pp.105-114
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    • 2007
  • Large span spaces have been widely used for various purposes including sports events in other countries. Due to increasing demands on multi-purpose use of such spaces, recently built large span sport facilities such dome stadiums have been required to accommodate sport events as well as performing events. Also, retractable ceilings and/or walls were generally adopted in those spaces for providing various event conditions. It seems obvious that the openings between diffuse fields and free field may cause difficulties in the acoustic design of such spaces In the present work, the acoustic characteristics of non-diffuse field has been investigated using 1/10 acoustic scale models. It was found that RTs at low- and mid-frequencies decayed faster than those at high-frequencies as the percentage of opening area increased. The decay rate of RTs at high frequencies were not influenced by increasing the area of an opening. Also high dependence of EDT on the percentage of opening area was observed at all frequency range. D50 was not improved by increasing the area of an opening up to 12.5% and then sharply increased. The application of Schroeder integration to evaluate the reverberation charateristics of coupled spaces may not be proper, since non-exponential decay process with double or triple decays of those spaces can not be properly defined. EDT seems more appropriate to predict reverberation at the early acoustic design stage of acoustically coupled spaces.

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Acoustic Characteristics of Sound Field in Partially Opened Rooms -Emphasis on Vertical Coupling of Diffuse and Free Field- (실내공간의 부분적 개방에 따른 음향특성변화 II -확산음장과 자유음장의 수직적 결합을 중심으로-)

  • Jeong, Dae-Up;Choi, Young-Ji
    • Journal of Korean Association for Spatial Structures
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    • v.7 no.5
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    • pp.75-82
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    • 2007
  • The present work measured and analyzed changes in the acoustics of a sound field which has a retractable ceiling. An 1/20 scale model of an openable space was built and measurement was carried out by varying the opened area of a ceiling. The most widely used room acoustic and design parameters, RT, EDT, and D50 were investigated. The results suggest that the use of RT as an acoustic design parameter may not be proper in an openable space and further it is likely to mislead the initial acoustic design of such spaces. It is mainly due to the characteristics of RT in which non-exponential decay processes are linearly fitted. Early decay times were found to be decreased in proportion to increaing the ratio of opened area. D50, an index of speech intelligibility, was effectively shows the influence of openings on the acoustics. It is also found that EDT and D50 at the seats, not directly exposed to the opened part of a ceiling, were almost linearly decreased in proportion to the ratio of opened area, while little influence was found for the opening ratio larger than 40% at the directly exposed seats to the opened part of a ceiling.

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A study on 3-channel binaural recording technique for 3D sound generation. (입체음향 생성을 위한 3채널 바이노럴 녹음기법에 관한 연구-)

  • 이신렬;성굉모
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.215-218
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    • 2000
  • 입체음향 생성을 위한 기존의 방법은 크게 바이노럴 녹음기법과 머리전달함수(HRTF)를 이용한 바이노럴 합성 기법으로 나눌 수 있다. 현재 바이노럴 기법은 기존 스테레오 시스템에 비해 공간감, 몰입감 측면에서는 탁월한 효과가 있지만, 음질의 저하와 정면 음상 정위가 잘되지 않는다는 치명적인 단점 때문에 프로페셔널 오디오 분야에서는 거의 사용되지 않고 몇몇 PC 게임용으로만 사용되고 있다. 본 논문은 정확한 정면 음상 정위를 위해 '3채널 더미헤드를 이용한 바이노럴 녹음기법' 을 제안하고, 기존 스테레오 녹음기법과의 호환성 유지를 위해 녹음 현장에서 직접 사용될 수 있는 3채널 더미헤드를 사용한 'Weighted Diffuse-field equalization 기법'에 대해 제안하며, 3 채널 더미헤드를 이용하여 기존 HRTF 데이터를 대체할 수 있는 정면 음상 정위에 강인한 '3 채널 더미헤드 HRTF 측정 기법'에 대해 제안한다.

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Wave Transmission Analysis of Semi-infinite Mindlin Plates Coupled at an Arbitrary Angle (임의의 각으로 연성된 반무한 Mindlin 판의 파동전달해석)

  • Park, Young-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.12
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    • pp.999-1006
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    • 2014
  • Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

The Analysis of Optimal Site Condition for Photovoltaic System and Green Roof Planting through Sunlight Component Simulation of Rooftop Area (옥상공간의 태양광 자원 해석을 통한 PV 시스템 및 녹화식재에 대한 적지조건분석)

  • Kim, Tae Han;Park, Dae Keun;Kwan, Ji Young
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.16 no.4
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    • pp.27-40
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    • 2013
  • These day morden cities have serious climatic problems due to enviornmental load caused by excessive development of urbanization. As technological improvement to answer to various ecological disasters and climate changes are also called on the field of construction, inter-disciplinary studies linked to the estabilishment of sustainable energy generation systems and enviornmental control is needed in a consilient point of view. This study aims to analyse optimal site conditions for photovoltaic system and green roof planting through solar radiation simulation in a integrated perspective. In so doing, it seeks to proffer basic study for developing a sound use of roof area that is sustainable in environmental and resources aspects. A computer simulation showed that, in the case of total seasonal solar radiation, summer season resulted 312.5kWh in 35% of total annual solar radiation. This season indicated the lowest radiation rate of the year for direct sunlight in 45.8% of total seasonal solar radiation. Due to such solar radiation simulation, at the largest optimal planting area, Glechoma hederacea var. longituba secured $719.16m^2$ of gross roof area.