• The Journal of the Acoustical Society of Korea
• /
• v.19 no.2
• /
• pp.73-82
• /
• 2000

This paper presents a significant improvement achieved in the acoustic characteristics of a conference room of I-company originally designed and built without consideration for room acoustic characteristics. The reverberation time of the room was excessive, which resulted in poor 'Definition' for speech. Thus the improvement of room acoustic characteristics was required. In this study, experiments and simulations using the principles of geometrical acoustics were executed to improve the acoustic characteristics in the room. By performing a series of simulation, it has become possible to predict acoustic parameters for an improvement plan. And the improvement plan of room acoustic characteristics was established. And for the verification of the simulation results, the experimental data were compared and evaluated against those from the simulation. Additionally, the proposed method in this paper demonstrated its effectiveness by successfully improving the room acoustic characteristics resulted from repair construction.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.4
• /
• pp.81-86
• /
• 2001

126-kHz bistatic sea surface scattering measurements were conducted in the shallow waters off the east coasts of Korea. The range from source to receiver was altered to change the scattering angle at the grazing angles of 38％ and 52％ . Unlike bottom scattering signal, the arrival time and the amplitude of sea surface scattering signals were varied due to the fluctuation of sea surface. The measured forward scattering strengths were compared to model predictions of Kirchhoff approximation and small slope approximation. In overall, the tendency of the scattering strengths showed reasonable agreement among the experimental data, Kirchhoff approximation, and small slope approximation.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.6
• /
• pp.66-72
• /
• 1996

In order to the sound effects and acoustics estimation of PANSORI hall, we are researched into the impulse response measuring and convolution integral of dry music(PANSORI) by using 1/10 scale model. Results are as follwo. First, impulse responses are measured by spark sound of electrodes and it is absolutely necessary many times of synchronous calculating for the obtain to enough S/N ratio. Second, a simulation technique of scale model is confirmed one of an effectual method of indoor acoustics estimation. Further, using the these new techniques and hearing test, its are recognized that reverberation time of PANSORI hall is about $1.0{\sim}$12.$ second suitable.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.568-571
• /
• 1997

The overall aim of this paper is to determine coupling loss factor using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one directional power flow between two sub structures. Using these conditions, it is possible to find the coupling loss factor equation. The comparison between theory of power transmission on conjunction and above equation, show a good agreement in simple beam structure. To check the effectiveness of above equation, it was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.5
• /
• pp.370-376
• /
• 2004

The overall aim of this paper is to determine coupling loss factor of welding point between shell and cylinder using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it ispossible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one way (uni-directional) power flow between multi-sub structures. Using these conditions, it is possible to find the equation of coupling loss factor expressed as above two loss factors. To check the effectiveness of above equation, this paper used two-stage application. The first approach was application between simple cylinder and shell. The next was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.2 s.107
• /
• pp.141-148
• /
• 2006

Korean traditional houses have 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 much natural and ecological to make the comfortable indoor climate than active systems of the present houses. This study aims to analyzed the acoustical characteristics of Korean traditional houses varied with lay out and floor plan to reflect the way of control for environmental condition. The reverberation time and level difference between rooms of the main living room and other main floored room, master room and kitchen are measured in each houses. As a result, the reverberation time of Korean 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. These above results show that our traditional house are much more emphasized seeking visual privacy of rooms than aural privacy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.969-972
• /
• 2003

The overall aim of this paper is to determine coupling loss factor of welding point between shell and cylinder using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one way(nl- directional) power flow between multi-sub structures. Using these conditions, it is possible to find the equation of coupling loss factor expressed as above two loss factors. To check the effectiveness of above equation, this paper used two stage application. The first approach was application between simple cylinder and shell. The next was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding Point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure

• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.5
• /
• pp.394-400
• /
• 2018

Various numerical methods have been adopted for indoor noise assessments of ship plant. Acoustical radiosity method is one of the high frequency approaches for acoustic field analysis, which assumes diffuse reflections by boundaries so that it could be efficiently applied to the acoustically diffused indoor space noise analysis. In this study, an acoustic field analysis program has been developed based on radiosity method, which could apply for acoustically large enclosures such as ship's indoor space. For this purpose, the procedure of the acoustical radiosity method has been summarized and implemented to an acoustic field analysis program using MATLAB. Numerical example for a rectangular indoor space has investigated validity of the implemented program. Steady state sound pressure levels calculated for a continuous acoustic source signal have shown good agreement with those by other solutions such as an analytic solution and a ray tracing method. Instantaneous sound pressure levels calculated for an impulsive acoustic signal have provided the clues of direct/reflected acoustic field and reverberation time.

• Journal of the Korean Institute of Educational Facilities
• /
• v.18 no.5
• /
• pp.3-11
• /
• 2011

In this study, the effect of treating 1-dimensional diffusers on the classroom acoustics was investigated to determine if the diffuser are beneficial for performing the preferred acoustical conditions for speech. A 1/10 scale model of a classroom was used to measure the acoustical parameters, T30, $C_{50}$, STI and SNR in that room. The room acoustical conditions were varied by treating diffusers either on the front or side walls of the classroom. When the diffusers were treated on the side walls around the student's areas, a shorter reverberation time at low frequencies was obtained and resulted in performing uniform reverberation times across the frequency bands. The $C_{50}$ values at mid- and high-frequencies were increased by treating the diffusers either on front or side wall surfaces. The highest STI and SNR values were obtained when the diffuser was treated on the front wall around the teacher's areas. It is found that diffusers are beneficial to increase the intelligibility of speech for the rear seats of the rooms.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.07b
• /
• pp.550-552
• /
• 2005

실감 재현이 중요한 가상현실 응용에서는 사용자에게 고급 그래픽 환경을 제시하고 사용자의 인터랙션에 즉각적인 피드백을 제공함으로서 실재감과 몰입감을 증대시키는 연구가 진행되어왔다. 실재감, 공간감 전달을 위해 시각과 청각을 함께 활용하는 것이 효과적이나, 가상공간의 특징을 반영한 3차원 사운도 재현 연구는 국내외 통틀어 초기단계에 머물러 있다. 실재감과 공간감을 반영한 3차원 사운드의 재현을 위해서는 음원의 전파, 반사, 잔향 풍의 계산이 사용자의 인터랙션에 따라 새롭게 계산되어야한다. 그러나 사운드 전파경로와 공간을 이루는 모든 폴리곤들과의 충돌을 검사하며 반사 등을 계산하는 것은 실시간성이 중요한 가상현실응용에서는 무리가 따르므로 실 시간성을 보장하기 위한 계산량 축소가 요구된다. 본 논문에서는 다수의 음원이 존재하는 복잡한 가상공간에서의 3차원 사운드를 재현하기 위하여 사운드 신과 계산에 필요한 최소한의 정보를 가지는 오디오 씬 그라프의 공간을 재구성하고 다수의 음원을 대상으로 음원 축소 및 군집화를 적용하여 3차원 사운드효과를 실시간으로 재현하는 알고리즘을 제안한다.