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남현도,서성대,황정현 한국조명전기설비학회 2001 조명·전기설비학회논문지 Vol.15 No.5
본 논문에서는 화력발전소 보일러 운전원 근무실 소음제어를 위하여 협대역 능동소음 제어시스템을 제안하였다. 제안된 시스템은 기준입력으로 구형파를 사용하여 기본파는 물론 고조파까지 한꺼번에 제어할 수 있게 하였으며, adjoint LMS 알고리즘을 사용하여 기존의 filtered-X LMS 알고리즘을 사용한 경우보다 계산량을 줄였다. 컴퓨터 시뮬레이션 결과, 기존의 광대역 능동소음 제어시스템에 비해 훨씬 작은 자수의 적응 필터를 사용하였으나, 더 우수한 특성을 보였다. In this paper, a narrowband active noise control system to reduce the noise in thermal power plants is proposed. The narrowband active noise control system contains rectangular wave generator and has a multi channel feed forward adaptive algorithms which uses the adjoint LMS algorithm. Although the effectiveness have been proven in the filtered-X LMS broadband active noise control system, this algorithm has much more computational complexity than that of narrowband active noise control system. The proposed active control system that uses the adjoint LMS algorithm, compared to the previous broadband active noise control system, not only is more effective in controlling narrowband noise but also has a more stable structure. Adaptive filter contains the FIR structure and IIR structure for primary and secondary path models. The simulation proves the effectiveness of the proposed algorithm.
다중채널 LMS 알고리즘을 이용한 자동차 내부 소음의 능동제어
남현도,서성대 단국대학교 2001 산업기술연구 Vol.2 No.-
In this paper, Multi-channel Active Noise Control(ANC) technique is proposed to cancel the noise from the inside of vehicle using engine. The algorithm used in the ANC system has better features for cancelling narrow and broad-band noise than conventional multi-channel ANC system. The broad-band ANC technique is especially applied in this study. The evaluation of the results through fft data processing after computer simulation about a closing space for experimentation is considered to verify the feasibility of the technique. The results shows that the noises measured from the engine inside of a vehicle were converged to low frequency band. Multi-channel LMS algorithm is used to remove the noises of the low frequency band. The results of the computer simulation show that the low frequency noises are reduced.
南炫道,魚鎭愚,陳永和 단국대학교 1993 論文集 Vol.27 No.-
A promising active noise control strategy, which is described, uses the LMS algorithm for adaptive digital signal processing. To work reliably it has to have a model of an acoustic transfer function of the environment in which it operates. Another LMS algorithm is used to identify this transfer function. The problems associated with carrying out this identification process continuously so as to track changes in the transfer function are investigated by means of a computer simulation. One configuration for such a system is presented along with results of simulations. Robust continuos identification system was presented which varied its level of identification signal (pseudo-noise) in response to the amount of identification error produced. In addition it switched off its identfication process once the error had been sufficiently reduced.
덕트내에서의 능동 소음 제거를 위한 Transducer의 최적 위치 선정
남현도,강택동 한국조명전기설비학회 1999 조명·전기설비학회논문지 Vol.13 No.1
제어용 스피커 및 검출용 마이크로폰 등 트랜스듀서들의 위치는 능동 소음제어 시스템의 성능에 큰 영향을 미친다. 능동 소음제어 시스템의 음향 특성이 매우 복잡하고, 유체 밀도, 복소 전파계수 등 음향 파라미터들의 값을 실제 적용 시에는 알 수 없는 경우가 많아 트랜스듀서들의 위치가 능동 소음제어 시스템의 성능에 미치는 영향을 해석적으로 구하기는 매우 어렵다. 본 논문에서는 트랜스듀서들 간의 전달함수들을 중첩의 원리를 이용하여 유도하였으며, 트랜스듀서들 간의 거리가 능동 소음제어 시스템의 성능에 미치는 영향을 컴퓨터 시뮬레이션을 통해 연구하였다. 단일극 시스템은 소음원과 제어 음원 사이의 거리에 영향을 받으며, 이중극 시스템은 두 제어 음원 사이의 거리와 소음원과 1차 제어 음원 사이의 거리에 많은 영향을 받는 것을 알 수 있었다. The attenuation property of active noise control system is much dependent on the locations of transducers. It is very difficult to retermine the orfunal locations of transducers analytically, because the acoustic behaviors in active noise control systems are very complex and the acoustic parameters, fluid density, corqJlex propagation, coefficients, etc., are usually unknown. In this paper, effects of positions of transducers and of distances between transducers on attenuation properties of active noise control systems is investigated via computer simulations. Tbe transfer functions between the transducers are derived using the superposition principle for computer simulations. Computer simulations show that the acoustic monopole and dipole systems for duct noise attenuation are sensitive to variations of the transducer location.
남현도,남일룡 단국대학교 1999 산업기술연구 Vol.1 No.-
This paper presents real-time implementation of a speech vocoder for ITU(International Telecommunications Union) H324 video telephony on the PSTN(Public Switched Telephone Network) using ITU G.723 16Kbps ADPCM(Adaptive Differential Pulse Code Modulation) algorithm. ITU H.324 is a new standard for low bit-rate multimedia communication that provides a foundation for interoperability and high quality video, voice and data based phone calls. The encoder using proposed algorithm accepts 8-bit PCM(Pulse Code Modulation) compressed sign민 and expends them to a 14-bit-per-sample for processing. The predicted values are subtracted from these 14-bit values to produced difference signals that are fed to the quantizer. Adaptive quantization is performed on the difference signals to produce a 2-bit output for transmission over the channel. At the decoder, the 2-bit transmitted values are used to update the inverse adaptive quantizer, whose output is a dequantized version of the difference signals. These dequantized values are added to the values generated by the adaptive predictor to produced the reconstructed speech signals. Computer simulations were performed to evaluate the performance of the speech vocoder that implemented by proposed algorithm.
다중채널 LMS 알고리즘을 이용한 3차원 폐공간에서의 능동 소음제어
南炫道,安東俊 단국대학교 1994 論文集 Vol.28 No.-
In this paper, the frequency characteristics of the model enclosure was found out by the mode analysis and active noise control experiments were carried out in the model enclosure. The transfer functions of primary paths, which are between the primary noise sources and error microphones, and the transfer functions of the secondary paths, which are between the secondary sources and error microphones, are estimated by the recursive least squares methods using the experiment data. The estimated transfer functions are applied to multi-channel least mean squre algorithm. The efficiency of the proposed algorithm was showed by computer simulations and experiments.