• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.206-211
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• 2000

Demands on a quiet environment is increasing because of noisiness and annoyance due to the extended use of noisy electronic device. Determination of sound power levels of noise sources using sound pressure in a reverberation room is usually a relevant method for devices with comparatively large volume or unevenly distributed source position. This study aims to observe the contents of ISO 3741 and analyze its changes in the revised standard ISO 3741-1999. And also aims to assess the revised ISO 1999 its effectiveness and limitations with an actual application to measure the sound power level of a refrigerator.

• The Journal of the Acoustical Society of Korea
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• v.3 no.2
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• pp.3-12
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• 1984

This paper is to suggest the optimum structure and the rating scale of PANSORI hall. The method of this study is as follows. 1. Consideration for the characteristics of OPANSORI and Beranek's music & acoustic theory. 2. To take advice from the expert. 3. The experiment and evaluation of a model. 4. The structure of PANSORI hall and the study of the availability in Beranek's rating scale of orchestra and opera. 5. The establishment of the rating scale in PANSORI hall. 6. The evaluation of the forms of performance in each hall. The result of this study, the proper hall in the performance of PANSORI is, 1. The initial time delay gap less than 25ms. 2. The reverberation time of the extents of 1.2 seconds. 3. The proper average bass ratio of 1.25 extents. 4. The distance from performers to audience is within 30 meters. 5. THE VOLUME OF HALL IS 450-7400 ㎥ extents. 6. It should be designed not to be a acoustical disturbancenoise, echo, and the unbalance of sound pressure level, etc.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.468-473
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• 2000

Recently the acoustic design has been considered the important part of architectural design. However, in the design of Catholic churches the exterior beauty is still main point. This study aims to find out the acoustical characteristics in the main hall of Catholic churches. Six catholic churches were selected for this experiment and the physical parameters which represent the acoustic characteristics of room were compared by the plan type and the architectural factor. The physical parameters compared and analyzed were SD(Stand deviation) of SPL(sound pressure level), RT(reverberation time), $D_{50}$(definition), $C_{80}$(clarity) and STI(speech transmission index).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.1037-1040
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• 2004

Sound and vibrations enter every aspect of our daily lives. Some, like music and verbal communications, soothe and relax us; others, such as the noise and vibration from traffic or machinery, can threaten our well being. The Rion Co., Ltd. was eslablished in 1944 as an affiliate of physics and acoustic pioneer, Kobayashi Institute of Physical Research. The RION lineup affords a full line of easy-to handle measuring, recording, and analyzing equipment with innumerable applications for monitoring and maintaining a comfortable environment. RION's concern takes in all manner of sound and vibration. Our activities extend from measuring reverberation time in concert halls and testing the soundproofing characteristics of housing materials to the control and maintenance of machine noise and vibration levels.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.2
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• pp.96-105
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• 1992

The objective of this paper is to study experimentally on the noise characteristics of supersonic jet from multihole orifice in the range of jet pressure from $at_g$ to $at_g$ in the reverberation room. At first, the single orifice jets are investigated for various hole diameter from 3.8mm to 10mm. Through the noise spectrum, the turbulent mixing noise and the shock associated noise is analyzed. The noise for confined jets into a tube of diameter 30mm or 90mm with length 2m is investigated in comparision with that for the free jets. The sound power level is measured and compared with thoretical models for free jet. At second, multihole orifice jets are investigated to study the effect of multijet on noise reduction. The spectrum and power level of multijets are measured and compared with single jets. The multi-jets in a confined pipe are also investigated. It is found that the noise spectrum is significantly altered by increasing the number of jet with decrease in jet diameter and also by confining the jet into tube.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.731-739
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• 2002

recently out door stadiums have been built as multi purpose stadium for athletic sports It hold but also various events and huge concerts. in the past, out-door stadium usually was built, but recently the out-door stadium which of the 50 ％ of roof covered by doom have been built increasingly. as the result, the sound obstacle is becoming very important. but a design of sound has become unplaned except some of the stadium, also rarely been built by sound-absorption material. as the result, the purpose of this study is investigating, analyzing the theory for plan of electric acoustic sound, a drawing of acoustic design and measurement a result value, comparison, evaluating a main sound factor with criteria of the Seoul City design. and reservation time, clearness, sound pressure level suitable for using purpose, so the necessary quantities will be added to financial budget of building acoustic design. and For verification, this contains acoustic analyser measurement and computer simulation and this study will find the solution of helping method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.340-349
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• 2016

A coupled room system consists of adjacent rooms and apertures where the sound energy is exchanged between the two rooms. Acoustically, a coupled room system shows a non-exponential decay profile. Most of the related researches have been to analyze the acoustic properties of two-room coupled system so far whereas three-room coupled system were seldom studied. In this regard, this paper aims to analyse the distribution of sound pressure level, sound decay curve of three-room coupled system and sound energy flow between them by using the acoustic diffusion model and to further verify them through experiments. Firstly, the sound pressure level distribution and mean sound pressure level in the steady-state condition are analyzed at various frequencies and source locations. Good agreements are observed in both experiments and analysis results. Secondly, two double slope effect quantifiers of sound attenuation, LDT/EDT and LDT/T10 are compared at various frequencies and for different source locations. The result indicates that LDT/T10, less affected by the early reflection patterns than LDT/EDT, is more suitable to the analysis and experiments of a multi-slope sound decay curve. Lastly, the sound energy flow in each room is analyzed based on the acoustic diffusion model. After the early decay stage, the sound energy is observed to flow from the room with a long reverberation time to the room with a short one.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.538-547
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• 2015

The goal of this study is to develop an algorithm to propose optimal deployment of detection sensor nodes in the target area, based on a performance surface, which represents detection performance of active and passive acoustic sonar systems. The performance surface of the active detection system is calculated from the azimuthal average of maximum detection ranges, which is estimated with a transmission loss and a reverberation level predicted using ray-based theories. The performance surface of the passive system is calculated using the transmission loss model based on a parabolic equation. The optimization of deployment configurations is then performed by a hybrid method of a virtual force algorithm and a particle swarm optimization. Finally, the effectiveness of deployment configurations is analyzed and discussed with the simulation results obtained using the algorithm proposed in this paper.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.422-428
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• 2018

Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.

• KIEAE Journal
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• v.6 no.1
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• pp.57-62
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• 2006

Korean Traditional houses has been evolved and developed in many years, adopting the natural environment to control exterior conditions. These control method are various passive system of using natural materials, considering micro climate, building lay out, and these system are more natural and ecological to make the comfortable indoor climate than active systems of the present houses. This study aims to analyzed control performance of outdoor environment of five Korean traditional houses during the summer and winter. These houses are varied with lay out and floor plan to reflect the way of control for environmental condition, surveyed the reverberation time and sound level difference between rooms of the main living room and other main floored room, master room and kitchen. Especially air temperature and humidity have been measured simultaneously in each rooms to compare with outdoor condition. As a result, the variation of air temperature and humidity of most rooms are considerably static while condition of outdoors are much varied, it is showed that indoor climate has been controled with traditional soiled walls.