• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1197-1202
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• 2001

Near-field acoustic holography is a powerful tool to visualize sound sources. This method requires pressure measurement at many points for a good hologram. Thus one has to measure carefully so that errors due to the uncertainty of position, sensor mismatch, and so on are reduced. A method to solve this problem is to use a well-designed measurement system. This paper introduces a sound visualization system at center for noise and vibration control (NOVIC), KAIST, and addresses the advantages in terms of the error reduction. The system consists of array microphones, array jigs, a system to control the position and the velocity of the jigs, a data acquisition system, and a monitoring system. This paper also shows some sound visualization results when the system is applied to a speaker and a computer. The results verifies that the sound visualization system is useful for identifying sound sources.

• 한국항공우주학회지
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• 제50권9호
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• pp.657-662
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• 2022

본 논문에서는 나로우주센터에서 운용 중인 원격자료수신장비의 G/T에 대한 시뮬레이션 활용 계산 결과와 측정 방법 2개에 대하여 분석하였다. 안테나 이득과 잡음 온도는 ICARA와 Antenna Noise Temperature Calculator를 이용하여 계산하였다. 시스템 G/T는 안테나 이득/잡음돈도와 LNA 이득/잡음온도, 케이블 손실을 반영하여 산출하였다. 첫 번째 G/T 측정 방법은 Y팩터 측정법으로 LNA 입력단에 안테나와 50ohm 터미네이션을 각각 연결했을 때의 신호 레벨 차이값을 LNA 열잡음 온도와 비교하여 G/T를 산출하는 방법이다. 두 번째 방법은 태양과 최저 레벨 지점을 바라보았을 때의 잡음 레벨 값 차이를 비교하여 G/T를 구하는 Solar Calibration 측정법이다. 마지막으로 G/T 계산결과와 두 측정법 비교를 통해 정확성을 검토하고 이로부터 안테나 성능, 운용환경에 따른 최적 측정법을 제시하였다.

• 센서학회지
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• 제23권1호
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• pp.7-14
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• 2014

Noncontact electrocardiogram (ECG) measurement using capacitive-coupled technique is a very reliable long-term noninvasive health-care remote monitoring system. It can be used continuously without interrupting the daily activities of the user and is one of the most promising developments in health-care technology. However, ECG signal is a very small electric signal. A robust system is needed to separate the clean ECG signal from noise in the measurement environment. Noise may come from many sources around the system, for example, bad contact between the sensor and body, common-mode electrical noise, movement artifacts, and triboelectric effect. Thus, in this paper, the extended Kalman filter (EKF) is applied to denoise a real-time ECG signal in capacitive-coupled sensors. The ECG signal becomes highly stable and noise-free by combining the common analog signal processing and the digital EKF in the processing step. Furthermore, to achieve ubiquitous monitoring, android-based application is developed to process the heart rate in a realtime ECG measurement.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.565-567
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• 2009

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.795-796
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• 2012

• 한국지능시스템학회논문지
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• 제23권6호
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• pp.505-510
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• 2013

본 논문에서는 현재 운영 중인 DGPS 기준국 환경에서 위성시계 이상 발생시 실시간으로 이상현상을 검출하고 식별하기 위하여, 기준국 수신기의 측정잡음을 최소화하는 기법에 대해 다룬다. 기준국 수신기의 측정잡음을 최소화하기 위하여, 의사거리 측정치에 포함된 오차항목을 제거하여 순수 측정잡음 만을 추정한다. 먼저 두 대의 기준국 수신기의 출력을 이용하여 비공통 성분 오차를 제거한 다음, 해당 보정치를 적용하여 측정잡음을 최소화시킨다. 측정잡음 최소화를 기반으로 위성시계 이상발생시 이상신호를 검출하고 이상위성을 식별하여 DGPS 기준국 시스템의 가용성을 증대시키고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.322-326
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• 2000

This paper is concerned with the development of remote vibration measurement system using the internet. Recently, various techniques are developed based on the advance of the internet environment. In this study, we developed the remote vibration measurement system using the internet server programming technique, the client programming technique, the GPIB programming, and the A/D, D/A programming techniques. Hence, we can control the measurement devices remotely. The feasibility of the system is validated using the experimental setup. The output of the D/A is connected to the small exciter and the piezoceramic sensor is connected to the A/D port. By sending out the exciting signal to the structure, we can collect the response. The experiment shows that the proposed idea works well. Another experiment consists of the function generator and the low-pass filter circuit. The wave form, amplitude, and the frequency of the function generator is controlled by the GPIB program and the output of the circuit is collected by the A/D port. The output is then displayed in HTML format.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1540-1548
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• 2000

Sound intensity techniques and ODS(Operational Deflection Shape) techniques are applied to identify the acoustic noise source of a hard disk drive and its control system. The sound intensity is used to visualize the noise source locations, and the ODS information to visualize the vibration pattern and to obtain the dynamic characteristics of the noise sources. The measurement systems are customized to accurately measure the sound intensity and ODS distributions of HDD system in space domains as well as frequency domains. The measurement systems for the sound absorption and transmission loss of materials are also used to support the background data for the efficient noise control. Using the visual information of source locations and its dynamic characteristics, the partial noise barrier structure and optimum absorption are designed and its controlled sound power level is proved to be under 3.1 Bel(Idle)/3.3Bel (Seek) which is the lowest level in the disk drive industry.

• 전력전자학회논문지
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• 제14권4호
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• pp.261-267
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• 2009

최대전력점 추적기는 태양광 발전시스템의 대표적인 기능이다. 최대 전력점을 추종하기 위해서는 태양전지의 전압과 전류의 측정을 필요로 한다. 만약 측정 신호에 노이즈가 포함되어 있으면 발생되는 전력이 감소되어 태양광 발전의 효율이 감소하게 된다. 노이즈가 포함된 신호에 확장 칼만 필터 이론을 적용하여 최적의 추정된 신호를 얻어 낼 수 있다. 칼만 필터는 랜덤 노이즈가 포함된 신호에서 최적의 신호를 얻어내는데 사용된다. 또한 칼만 필터의 적용결과로 인덕터 전류와 같은 측정하지 않는 신호도 센서리스 추정이 가능하다. 본 논문에서는 시스템 모델링 방법과 확장 칼만 필터 설계 방법이 소개된다. 실험 결과로서 제안된 제어기의 성능을 확인하였다.

• 한국소음진동공학회논문집
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• 제23권12호
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• pp.1056-1065
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• 2013

Noise generated from Construction site has been raised most civil complaints to 64.4 % among the environmental pollution in 2011. Therefore, local government recommends and prescribes that construction sites over a certain scale install sound level meter for noise monitoring. For example, Seoul has implemented a 24 hour noise monitoring system, with real time communication, to the large construction sites more than 10,000 $m^2$ from the end of August 2012. But it is difficult to use noise measurement data for the construction noise assessment, since the installation standards and technical specifications for construction noise monitoring system are not presented. In this paper, we proposed noise monitoring system improvement plan including technical specifications and installation standards using the investigating results of the problems of current noise monitoring system and the foreign cases.