• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.165-168
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• 2000

Engine noise is one of the major causes of the interior noise, and so has been studied in various ways in recent days. Recently air induction noise has been extensively studied to reduce the engine noise. Conventional method to reduce the noise is adding several resonators to the induction system. However this causes a reduction of engine output power and an increase of fuel consumption. Thus in this study, the feasibility of applying the active noise control to the induction system is studied to the overcome the above disadvantage.

• 대한기계학회논문집
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• 제18권9호
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• pp.2265-2271
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• 1994

With the improvement of standard of living, requirement for comfortable and quiet environment has been increased and, therefore, there has been a many researches for active noise reduction to overcome the limit of passive control method. In this study, active noise control is performed in a duct system using intelligent control technique which needs not decide the coefficients of high order filter and the mathematical modeling of a system. Back propagation algorithm is applied as an intelligent control technique and control system is organized to exclude the error microphone and high speed operational device which are indispensable for conventional active noise control techniques. Furthermore, learning is performed by organizing acoustic feedback model, and the effect of the proposed control technique is verified via computer simulation and experiment of active noise control in a duct system.

• 한국소음진동공학회논문집
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• 제12권1호
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• pp.12-20
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• 2002

To control the noise of an enclosed sound field, we built a state space model using the acoustic modal parameter description. Using the state space model, we can investigate the controllability and observability, and find an appropriate position of control speaker and microphone to control sound field of the enclosed space. We implemented LQR(linear quadratic regulator) controller and reduced order observer to reduce the first acoustic mode. Experiments showed satisfactory results of 4∼10 dB reduction of magnitude of the first acoustic mode, and support the feasibility of the proposed scheme to lightly damped acoustic field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.565-570
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• 2000

In order to make a quiet zone, one can consider methods to generate a secondary sound field that cancels a primary sound field. Active noise control (ANC) is one of the kinds. This paper mainly deals with the issues on determining the optimal positions of control sources and sensors for making a desired quiet zone. The issues address the reason why the positions are important, how the positions are optimized, and what the measure on the optimal positions is in an uncertain sound field. It is also shown that a power control is applicable to a specific uncertain sound field. In addition, this paper shows that a control material method, which passively changes a boundary condition, is essentially found to be on the same road of ANC.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 2호
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• pp.433-438
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• 1999

본 논문은 기계장치에서 발생하는 소음 중 불필요한 소음만을 제거하고 실제로 필요한 소음(경고음 작동음 등)의 정보를 가진 소리는 제거하지 않는 소음 제어 방법을 Active Noise Control(ANC)를 이용하여 구현하였다. 소음원으로는 축류팬(Akial Fan)을 사용하였으며 여기서 발생하는 BPF를 효과적으로 제어할 수 있는 Feedback Active Noise Control 방식을 사용하였으며 적응 알고리즘으로 Filtered-X LMS 알고리즘을 사용하였다. 실험은 두 가지 Case(덕트 내 전파 소음, 외부 자유 음장 방사 소음)로 실행되었다. 제거하고자하는 대상은 BPF 소음이며 이 이외의 주파수에는 영향을 주지 않게 하기 위하여 대역필터를 이용하였다. 또한 실제 인간이 느끼는 소음 감소 효과를 알아보기 위해 Loudness로 제어 전후의 결과를 비교하였다. 실험 결과 BPF만 감소시키고 BPF이외의 주파수에는 영향을 주지 않음을 알 수 있었으며 6.7dB의 Loudness level의 감소 효과를 얻어, 제어하고자 하는 주파수만을 제어하였으며 음압뿐 아니라 인간이 느끼는 소음도에서도 효과적으로 감소할 수 있음을 확인할 수 있었다.

• 소음진동
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• 제8권6호
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• pp.1030-1036
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• 1998

When the lateral dimensions of a duct is larger than or comparable to the wavelengths of Interest, higher order modes propagate in the duct. These modes will be radiated and produce noise. A number of sensors and actuators for control of radiating noise from the duct have to be incorporated with the number of modes which one wants to control. These considerations motivated the present study that considers a control system which has less microphones and control sources than required. In this work, by theoretical analysis, the control performance of such a kind of system is investigated in terms of sound-field variables and control system variables. The possible maximum and minimum value. mean and variance of residual acoustic potential energy are derived for the set of primary sound fields.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.763-768
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• 2012

Active window system which can reduce the environmental noises, such as traffic noise and construction noise, from an open window into a room was proposed in the previous works. The key idea of the proposed active window system was that the control sources are approximately collocated with the primary noise source in terms of the acoustic power for global noise reduction throughout the interior room. Moreover, because it is important not to intrude into the living space in the building environment, no error sensors were used and an open-loop control method using control sources at the window frame and the reference sensors outside the room was used for the proposed system. The open-loop control gain was calculated by the interior room model assumed as the semi-infinite space, and the interior sound field was estimated by Rayleigh integral equation under the baffled window model assumption. However, windows with a finite thickness should were considered for the calculation of the open-loop control gain of the active window system since these are representative of most window cases. Therefore, the finite thickness window model based on the Sgard's model was derived and the open-loop control gain using the interior sound field estimated by that model was calculated for active window system. To compare the performance of these two models, a scale-model experiment was performed in an anechoic chamber according to noise source directions. Experimental results showed that the performance for the thickness window model is better than the baffled window model as the angle with respect to the perpendicular direction is larger.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1378-1388
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• 2005

Spatial control of sound is essential to deliver better sound to the listener's position in space. As it can be experienced in many listening environments. the quality of sound can not be manifested over every Position in a hall. This motivates us to control sound in a region we select. The primary focus of the developed method has to do with the brightness and contrast of acoustic image in space. In particular, the acoustic brightness control seeks a way to increase loudness of sound over a chosen area, and the contrast control aims to enhance loudness difference between two neighboring regions. This enables us to make two different kinds of zone - the zone of quiet and the zone of loud sound - at the same time. The other perspective of this study is on the direction of sound. It is shown that we can control the direction of perceived sound source by focusing acoustic energy in wavenumber domain. To begin with, the proposed approaches are formulated for pure-tone case. Then the control methods are extended to a more general case, where the excitation signal has broadband spectrum. In order to control the broadband signal in time domain, an inverse filter design problem is defined and solved in frequency domain. Numerical and experimental results obtained in various conditions certainly validate that the acoustic brightness, acoustic contrast, direction of wave front can be manipulated for some finite region in space and time.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.737-742
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• 2007

The method of the reducing duct noise can be classified by passive and active control techniques. However, passive control has a limited effect of noise reduction at low frequencies (below 500Hz) and is limited by the space. On the other hand, active control can overcome these passive control limitations. The active control technique mostly uses the Least-Mean-Square (LMS) algorithm, because the LMS algorithm can easily obtain the complex transfer function in real-time particularly when the Filtered-X LMS (FXLMS) algorithm is applied to an active noise control (ANC) system. However, the convergence performance of the LMS algorithm decreases slightly so it may delay the convergence time when the FXLMS algorithm is applied to the active control of duct noise. Thus the Co-FXLMS algorithm was developed to improve the control performance in order to solve this problem. The Co-FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Co-FXLMS algorithm is presented in comparison with the FXLMS algorithm. Simulation results show that active noise control using Co-FXLMS is effective in reducing duct noise.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.379-380
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• 2013