• The Journal of the Acoustical Society of Korea
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• v.17 no.3
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• pp.52-58
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• 1998

본 논문에서는 시간 지연이 없는 서브밴드 필터 구조를 사용한 능동 소음 제어 시 스템을 제안하였다. 제안된 시스템은 기준 입력 신호와 2차 경로의 전달 함수를 컨볼루션하 여 만들어지는 filtered reference 신호가 서브밴드내에서 생성될 수 있도록, 2차 소음원과 오차 센서 사이의 전기·음향학적인 경로를 나타내는 2차 전달 함수를 각 서브밴드로 재구 성함으로써, 알고리듬 구현시 계산량을 감소시킨다. 또한 2차 경로의 전달함수가 시간에 따 라 변화하는 경우에도 능동 소음 제어 시스템의 소음 제어 성능을 유지할 수 있도록, 각 밴 드마다 두 개의 적응필터를 사용한 on-line 시스템 인지 구조를 제안하여 on-line 시스템 인 지에 필요한 계산량을 감소시켰다. 본 논문에서 제시한 능동 소음 제어 시스템의 제어 성능 과 on-line 시스템 인지 성능을 모의 실험을 통하여 검증하였다.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.121-122
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• 2008

본 논문에서는 2차 경로의 추정을 통하여 안정성이 강화된 능동소음 제어 시스템을 제안한다. LMS 알고리즘은 구조가 단순하고 계산량이 적은 장전이 있지만, 광대역 소음원에 적용할 경우 수렴 성능이 좋지 않은 단점이 있으며, 2차 경로 및 소음원 입력의 파워가 시변 할 경우 적응 알고리즘의 안정성이 약화되는 문제점이 발생한다. 본 논문에서는 지속적으로 누적 오차를 추적하여 일정 값 이상으로 증가하면 자동적으로 2차 경로 전달함수를 새로 추정하는 자동오프라인 추정 기법을 제안하였다. 공조용 덕트에 광대역 소음을 적용하여 제안된 능동소음제어 시스템을 실험을 수행한 결과 우수한 특성을 얻었다.

• The Journal of the Acoustical Society of Korea
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• v.12 no.1E
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• pp.12-19
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• 1993

덕트에서의 능동소음감쇄 문제를 다루었다. 음향귀환이 있는 경우의 덕트를 중첩의 원리를 이용하여 모델링하였다. 본 논문에서 다루어진 능동소음제어를 위한 덕트모델은 consistent하다고 가정했다. 스피커와 오차 마이크로폰 사이의 2차 경로 전달함수를 추정하기 위한 새로운 알고리즘을 제안했으며 제안된 알고리즘은 기존의 알고리즘보다 계산양이 작아 다중 채널 능동소음제어에도 이용될 수 있으리라 생각된다. 제안된 알고리즘의 효율성을 보이기 위하여 컴퓨터 시뮬레이션을 행했다.

• The Journal of the Acoustical Society of Korea
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• v.27 no.4
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• pp.207-214
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• 2008

To create 3D sound, we usually use two methods which are two channels or multichannel sound systems. Because of cost and space problems, we prefer two channel sound system to multi-channel. Using a headphone or two speakers, the most typical method to create 3D sound effects is a technology of head related transfer function (HRTF) which contains the information that sound arrives from a sound source to the ears of the listener. But it causes a problem to localize a sound source around a certain places which is called cone-of-confusion. In this paper, we proposed the new algorithm to reduce the confusion of sound image localization. HRTF grouping and psychoacoustics theory are used to boost the spectral cue with spectrum difference among each directions. Informal listening tests show that the proposed method improves the front-back sound localization characteristics much better than conventional methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.301-306
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• 2011

In this paper, active noise barriers for attenuation of road noise are proposed. multi-channel audio systems, DAQ part and high performance DSP H/W were designed. Active noise control firmware programs were implemented for multi-channel off-line/on-line estimation methods for secondary path transfer functions and FIR/IIR filter structure are used main noise control algorithms. To evaluate performance of proposed systems, the experiments were performed in an active noise barrier test bed for various noise cases.

• Journal of KIISE:Information Networking
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• v.37 no.2
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• pp.109-121
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• 2010

Recently, the military of Korea has been establishing the next generation wireless tactical communication system so called Tactical Information Communication Network (TICN). A routing protocol for TICN transport networks has to be able to select a path with high survivality, reliability, and stability while accommodating as many flows as possible with minimum QoS guarantees. The OSPF(Open Short Path First) used widely is determined to be the routing protocol for TICN. With the typical deployment practices OSPF, however, it cannot satisfy the requirements of TICN. In this paper, we propose a cost function for OSPF and a way to tune the OSPF protocol parameters for the TICN transport networks. Through simulations, it is shown that the OSPF with the proposed cost function provides better performance than the OSPF in terms of both the services provided to the applications and the network resources utilization.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.570-575
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• 2019

Active muffler is implemented by applying active noise control technique to reduce exhaust noise of automobile muffler. Conventional Filtered_x LMS algorithm has a problem that the degree of control filter becomes very large and convergence deteriorates when acoustic feedback is present. The recursive LMS algorithm can compensate for this problem because it can be easily diverted in the adaptive filter adaptation process. In this paper, the structure of the primary path and the secondary path transfer function is designed as the IIR filter to improve the convergence performance and the computational burden, and the stabilization filter algorithm is applied to secure stability which is a disadvantage of the IIR filter structure. The stabilization filter algorithm plays a role of pulling the pole into the unit circle to prevent the pole of the transfer function corresponding to the acoustic feedback from diverging during the adaptation process. In this way, the computational burden of the active muffler system and the convergence performance can be improved. In order to show the usefulness of the proposed system, we compared the performance of the proposed Filtered_x LMS algorithm with the performance of the proposed system for the exhaust sound of a diesel engine, which is a variable environment. Compared to conventional algorithm, proposed algorithm's computational burden is less than half, and convergence performances are more than 4 times.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.4
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• pp.47-51
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• 2003

Due to the asymptotic property, deadbeat control which is well used in digital control system can not be applied to the continuous time system. But recently by use of the finite Laplace Transform to transfer function and establishment of some settling conditions, CDBC(Continuous time Deadbeat Control) is studied. For CDBC design, transfer function is constituted with delay elements and then order and interpolation conditions are derived. In other way, digital deadbeat controller is implemented and it's output is changed to continuous type by smoothing elements. In this paper multirate sampling is used and so inner controller is sampled faster than output feedback loop. And End order smoothing elements is placed to the output of digital deadbeat controller. By the multirate sampling overall output response is improved. The controller is impleneted as a serial integral compensator in the forward path and a local feedback compensator introduced into the outpute feedback loop. Matlab Simulink is used for simulation.

• Journal of Korea Water Resources Association
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• v.48 no.2
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• pp.91-103
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• 2015

This paper presents the systematic approach to positively skewed shape of instantaneous unit hydrograph (IUH), that is one of the universal features of hydrologic response function. To this end an analytical expression of statistical moments for IUH is derived within the framework of geomorphologic instantaneous unit hydrograph (GIUH) theory and quantified according to the concept of hydrodynamic, geomorphologic and kinematic heterogeneity. There is a big scale difference between hillslope and channel flow path system. Although the former has the much smaller level of scale its variation coefficient tends to be higher and coefficient of skewness has the different trend than the latter. The shape of IUH is likely to be much more affected by kinematic heterogeneity rather than hydrodynamic heterogeneity and its combined effect with geomorphologic heterogeneity is the major cause of skewing hydrologic response function. Statistical features of hillslope and channel flow path can be transferred into hydrologic response function in the form of dimensionless statistics and their relative importance forms the general shape of hydrologic response function.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.46-54
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• 2021

In this paper, active noise control was performed to reduce radiated noise in the low frequency band of dishwashers. First, through an analysis of the noise environment of the dishwasher, it was confirmed that the pump noise contributed the most to the radiated noise in the low frequency band, From the result of the noise environment analysis, the reference signal was selected to be the vibration signal of the pump body. The reference signal was obtained by using the accelerometer on the pump body, which can prevent acoustic feedback. The error signal sensor was selected as a microphone located at 1 m in front of the dishwasher and 0.5 m in height. And to design the controller, the error signal and the reference signal were measured at the operational rpms of the dishwasher at 2,500 rpm, 2,600 rpm and 2,800 rpm, and the secondary path transfer function was measured. The designed controller was mounted on Digital Signal Processor (DSP) equipment, and the control performance was verified experimentally. As a result of the measurement at the 3 operational rpms, the 7th multiple component of pump operating frequency decreased by 1.93 dB, 4.43 dB, 5.15 dB per rpm, and the 12th multiple component decreased by 6.67 dB, 2.34 dB, 4.28 dB per rpm. And overall Sound Pressure Level (SPL) decreased by 0.84 dB, 2.58 dB, 1.48 dB by rpm.