• Title/Summary/Keyword: Active reflection control

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Study on Sound Reflection Control using an Active Sound Absorber (능동흡음재를 이용한 음파반사 제어기법 연구)

  • Chang, Woo-Suk;Gweon, Dae-Yong
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.8
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    • pp.806-814
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    • 2009
  • This paper reviews a study about sound reflection control using an active sound absorber. An active sound absorber includes sound transmitting and receiving piezocomposite sensor layers molded by water tight epoxy, and connected with a feedback controller. The multi-layer sensors and the controller consists a closed feedback loop, whose intrinsic characteristics shows excellent impedance matching performance within specified frequency band, and consequently, minimizes reflection waves. Multilayer sound transmission model is derived based on one dimensional model, and its performance is verified with experiment using a pulse tube setup.

A single sensor based active reflection control system using FxLMS algorithm (FxLMS를 이용한 단일 센서기반 능동 반향음 제어 시스템)

  • Kim, Jaepil;Ji, Youna;Park, Young cheol;Seo, Young soo
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.1
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    • pp.57-63
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    • 2017
  • This paper presents an active acoustic-reflection control algorithm based on a single sensor. The proposed algorithm operates in a system comprising a single sensor located nearby the reflective surface and a control transducer mounted on the reflective surface. First, the incident and reflected acoustic signals are separated from the sensor signal, and a control signal is generated using the separated signals. For the signal separation, the proposed algorithm requires the response of the reflection path which is estimated from the acoustic response between an external sound source and the sensor. Finally, the control filter is adjusted using the FxLMS (Filtered-x Least Mean Square) algorithm. To verify the effectiveness of the proposed algorithm, it was implemented in real time using a DSP (Digital Signal Processing) board, and the experimental results obtained in one-dimensional air-acoustic environment show that the reflections of the 1 kHz burst can be reduced by 11.6 dB.

A design of optimal filter for single sensor based acoustic reflection control (단일 센서 기반 반향음 제어를 위한 최적 필터 설계)

  • Jeon, Shin-Hyuk;Ji, Youna;Park, Young-cheol;Seo, Young-Soo
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.5
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    • pp.353-360
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    • 2017
  • The single sensor based acoustic reflection control system separates the incident and reflected signals from the single sensor output, and reduces the reflected signal by generating an out-of-phase signal from the incident signal component. In this paper, we propose an optimal filter design method for a single sensor based reflection control system. In the proposed method, it is shown that the optimum control filter design is possible by using the measured impulse responses of the reflection and control paths. The reflection control algorithm based on the proposed optimal filter achieves better performance than the conventional adaptive filter-based algorithm and effectively controls the reflection without the initial convergence time. We performed computer simulations using the signals obtained in a 1-dimensional acoustic duct environment, and from the simulation results, it was confirmed that the proposed optimal filter has robust performance even in noisy environment.

A New Ultrasonic Range Sensor Using Multiple Reflections (다중반사특성을 이용한 새로운 초음파 거리 센서)

  • Lee, Wang-Heon;Gwon, In-So
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.7
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    • pp.564-572
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    • 2002
  • This article describes the ultrasonic range sensor for the recognition of the Indoor environment, especially utilizing the multiple reflection properties of the sonar usually ignored as disturbances or noises. In this paper, we endow the ultrasonic range sensor with the active motion using the stepping servomechanism in order to get the multiple reflections with environment objects. Environment features such as target type, distance and azimuth based on the scanned one frame data of that multiple reflection patterns are recognized simultaneously.

Real-time impletation of active adaptive noise controller (능동 적응 소음 제어기의 실시간 구현)

  • 이종필;장영수;서진현;정찬수
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10a
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    • pp.831-836
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    • 1990
  • Real-time implementations of active noise controller are proposed and tested. For compensation of time delay of feed-back path, the n-step ahead prediction is applied. And predicting source noise and reflection noise respectively, reflection noise can be cancelled. For real-time processing, the DSP56001(Digital Signal Processor) is used. Experimental results show that the proposed controller is stable and of good performance.

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Modeling and Target Classification Using Multiple Reflections of Sonar (초음파의 다중 반사 특성을 이용한 표식 모델 및 분리)

  • Kweon Inso;Lee Wangheon
    • Journal of Institute of Control, Robotics and Systems
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    • v.10 no.9
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    • pp.779-784
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    • 2004
  • This paper describes a sonic polygonal multiple reflection range sensor (SPMRS), which uses multiple reflection properties usually ignored in ultrasonic sensors as disturbances or noises. Targets such as a plane, corner, edge, or cylinder in indoor environments can easily be detected by the multiple reflection patterns obtained with a SPMRS system. Target classification and feature data extraction, such as distance and azimuth to the target, are computed simultaneously by considering the geometrical relationships between the detected targets, and finally the environment model is generated by refining the detected targets. In addition, the narrow field of view of a sonar range sensor is increased and the scanning time is reduced by active motion of the SPMRS stepping servomechanism.

Effect of an emitting-layer height on a photon extraction efficiency in LED (LED에서 발광층의 높이가 광추출 효율에 미치는 영향)

  • Kwon, Keeyoung
    • The Journal of the Convergence on Culture Technology
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    • v.7 no.1
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    • pp.564-569
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    • 2021
  • In this paper, for the typical LED and the tilted LED, when there is no electrode, when 20% absorption (80% reflection) occurs at the electrode, and when 60% absorption (40% reflection) occurs at the electrode, the effect of the absorption at the electrode and the height of the active region on the photon extraction efficiency and the mean photon path length was investigated, and an appropriate height of the active region was proposed. In a typical LED, as the absorption of the electrode increases, the photon extraction efficiency decreases from 18% to 15% and 13%, and the photon extraction efficiency is highest when the height of the active area is located in the center between the two electrodes. In the tilted LED, as the absorption of the electrode increases, the photon extraction efficiency decreases from 38% to 33% and 25%, and the photon extraction efficiency is highest when the height of the active area is located in the center between the two electrodes. The tilted LED can increase the photon extraction efficiency more than twice than that of a typical LED, where photons are trapped inside the chip due to total reflection.

Adaptive Re-reflecting Wave Control In Plunger Type Wave Maker System: Experiments In Two Dimensional Wave Basin

  • Park, Gun-Il;Kim, Ki-Jung;Park, Jae-Woong;Lee, Jin-Ho
    • Journal of Ship and Ocean Technology
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    • v.7 no.1
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    • pp.13-18
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    • 2003
  • The control performances for active re-reflecting wave control suggested in the previous paper have been verified in cases of regular and irregular waves in a real two dimensional wave basin. For regular waves, the control performances are investigated in terms of reflection coefficients, expected amplitudes of propagating waves and wave absorbing capabilities after cessation of wave generation, compared with those of no-control cases. For irregular waves similar verification procedures were adopted. Though there are certain constraints due to the geometrical non-linearity of wave maker and certain nonlinear characteristics due to the near field and gravity waves these experiments show that the control logic could be useful in realizing re-reflecting wave control in conditions of real wave basin.

Active Noise Control in a Duct With Reflected Wave (반사파가 있는 관내의 능동 소음제어)

  • 오상헌;김양한
    • Journal of KSNVE
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    • v.4 no.2
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    • pp.187-198
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    • 1994
  • This study is to describe the effects of the duct termination conditions conditions upon the active noise attenuation system. The adaptive filtering algorithm using FIR filter is implemented for duct noise attenuation. To avoid the instability caused by the acoustic feedback, two methods are considered. One is to use a compensating FIR filter. The other is to utilize uni-directional detecting microphone and uni-directional control speaker. Experimental results show that the reflections of sound from duct terminations greatly reduce the performance of ANC system. The directionality of detecting microphone and control speaker is a major factor to decide ANC performance. When there are some reflections from both duct terminations, the noise attenuation using finite FIR filter is not enough to model the duct plant. Especially, the reflection from the upstream termination reduces the noise attenuation in the frequencies related to the distance between control speaker and upstream termination. The performance of the noise attenuation is found to be largely enhanced by using uni-directional coupler, both on detecting microphone and control speaker, even if the duct system has an arbitrary termination conditions.

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Quiet Zone Generation by Absorption Materials (흡음재 배치를 이용한 정숙 공간 형성 방법)

  • Park, Joo-Bae;Kim, Yang-Hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.11a
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    • pp.403-408
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    • 2000
  • An acoustic field in a 3 dimensional enclosure is caused from interference between sound sources and the complex reflections from wall. Therefore, changing an acoustic property of wall such as admittance means generating another acoustic field. The purpose of this paper is utilizing the characteristic to make a quiet zone. First, this paper shows that the control material is essentially on the same road as active noise control(ANC). That is, we can consider the control material as the control source of ANC. However we cannot control the reflection strength of it. Second, through a numerical simulation, this paper shows that the position of the control material is an important variable of the control.

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