• Title/Summary/Keyword: Beating noise

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Beat Map Drawing Method for a Large Size Bell using ODS (ODS를 이용한 대형종의 맥놀이 지도 작성법)

  • Park, In-Seok;Lee, Jung-Hyeok;Park, Sun-Mi;Kim, Seock-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.04a
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    • pp.929-932
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    • 2012
  • Beat map shows the distribution property of the beating sound in the bell structure. Using the beat map, beat control and beat estimation are available. To draw the beat map, mode pair parameters of the bell are required. However, in case of large bell which is struck by a heavy wooden hammer, it is very difficult to measure the excitation force and to obtain the mode pair parameters. In this paper, we determined the mode pair parameters of the bell from the transmissibility between the roving signal and reference signal, using ODS(operational deflection shape) method. The mode pair data are input to the theoretical model of the beat response and beating waves are generated on the bell circumference. All the numerical and beat map drawing procedures are automatized using Matlab. Finally, the reliability of the beat map generated by the program is verified.

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Analysis of a wavelength tunable source according to temperature variations in a Mutually Injected F-P LD (상호주입 잠김 F-P LD에서 온도변화에 따른 가변 파장 광원의 특성 분석)

  • Hwang, Ji-hong;Oh, Yeong-guk;Lee, Hyuek-jae;Lee, Chang-hee
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2012.10a
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    • pp.1009-1011
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    • 2012
  • In this paper, a wavelength tunable light source based on mutually injected locking with two F-P LDs, has been constructed and then analyzed for wavelength shift and RIN (Relative Intensity noise) according to temperature. We have measured maximum about 2 nm for the wavelength shift and minimum -110dB/hz for the RIN. Also, the RIN and beating noise in eye patterns are increased by changing temperature high.

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Evaluation of the Outdoors side Air-conditioner Sound using Time Signal Analysis (Time signal 분석을 통한 에어컨 실외기의 소음 평가에 대한 연구)

  • 한형석;구형모;모진용;박득용;김주환
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.330-332
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    • 2003
  • In this paper, It is introduced new sound quality method, FI(Fluctuation Index) and the example applied Outdoors side Air-conditioner noise evaluation. Because FI is applied with very simple algebraic calculation algorithm, it can be applied some other application without spending high time and cost.

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Analysis of Shock Mechanism and Actuator Behavior of HDD (내충격성 향상을 위한 HDD Actuator의 거동 연구)

  • 손진승;좌성훈;이행수;홍민표
    • Journal of KSNVE
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    • v.11 no.3
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    • pp.449-454
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    • 2001
  • The shock performance of hard disk drives has been a serious issue for portable computers and AV application HDD. Focusing on the motion of an actuator, we investigated non-operational shock mechanism and studied several parameters that affect the shock performance by experimental analysis. It was found that there are two important factors fort the actuator to endure high shock revel. One is a shock transmissibility and the other is a beating between the arm blade and the suspension. To generalize the shock transmissibility, the concept of shock response spectrum was introduced. The shock response spectrum of the actuator system was obtained experimentally and compared with that of an analytical single degree of freedom model. It was found that there was a good agreement. The first bending natural frequency of the arm blade was found to be the most important factor for the low shock transmissibility. By applying the shock response spectrum and avoiding the beating, we could design an actuator of high shock performance.

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A study on the reduction of noise and vibration by acoustic resonance in the tube bank of a circulating fluidized bed combustion boiler (순환 유동층 보일러 관군의 음향공진에 의한 이상소음 발생 및 저감 연구)

  • Park, Eung-Kyu;Song, Keun-Bok;Kim, Won-Hyun;Joo, Won-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.101-106
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    • 2011
  • In the present paper, the phenomena of abnormal noise and vibration due to acoustic resonance of CFBC(Circulating Fluidized Bed Combustion) boiler was presented. The acoustic resonance which occurred in the gas path of CFBC boiler system was caused by coincidence of vortex shedding frequency of tube bank and acoustic natural frequency of duct and hopper. And, the phenomena of beating arose from the interference of two closed resonant waves at 66.4Hz and 70.8Hz. There are two control methods for acoustic resonance in this system. The first method is to change the vortex shedding frequency from the structural alterations on the tube bank. And the second method is to change the acoustic natural frequency of the gas path with the installation of anti-noise baffles. The second one which is relatively easy to apply, was adapted in this study. As a result, the noise and vibration level have been decreased by 41dB and 94% at 66.4Hz, respectively. And the improvement of noise and vibration at 70.8Hz was identified by sensory evaluation.

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Analysis and Suppression Plan for Structure and Flow induced Noise in a Small Refrigeration System (소형 냉동시스템 소음의 구조와 유동 연성 분석과 저감 방안)

  • Kim, Soo-Hyun;Lee, Dong-Yeon;Lee, Moo-Yeon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.11
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    • pp.4129-4136
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    • 2010
  • This paper addresses how to reduce or redesign uncomfortable sound from small refrigerator by modifying some structures in mechanical components or operating conditions. After performing vibration analysis on each component and then sound analysis are carried out. From stepped designed experiments, we could acquire some important results that structure and flow induced vibration assumed to be a major cause to noise level and frequencies. Modifying some mechanical structure and operating conditions, uncomfortable starting noise and beating sound are suppressed. Machinery room located in refrigerator's backside is investigated for vibration and noise suppression, and some ideas for more improvement are suggested.

A Study on Subjective Nise Evaluation of Rdesidential Area on Aircraft Noise near Airport - Case Study on Taegu Airport - (공항 인근주민들의 항공기소음에 대한 피해의식 구조에 관한 연구 - 대구공항을 사례지역으로 -)

  • 김재석
    • Journal of KSNVE
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    • v.10 no.1
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    • pp.41-48
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    • 2000
  • Evaluation model for damage consciousness was established through the survey of 2,210 residents' consciousness on aircraft noise near Taegu Airport. There were none who replied that the level of the aircraft noise was as los as it was quiet. 77(3.5%) people replied the noise was normal, and 2,133(95.5%) people said it was noisy. As to the period of time when the aircraft noise occurred, 51%, 97%, 86%, 0.6% of the residents pointed out the morning time, the day time, the evening time, and the night time, respectively. Because of aircraft noise, 73%, 88%, 70%, 77%, 78%, and 33% of the residents felt it disturbing indoor conversation, telephoning, watching TV or listening to the ratio, reading or meditating, working, sleeping, and studying, respectively. It was examined that the bad effects of aircraft noise on the health were severe : 43% of the resident said they experienced embarrassment. 52% astonishment, 66% absence of mind, 61% heart-beating. 77% headaches, 78% earache, and 93% displeasure. For the survey of the residents' damage consciousness about aircraft noise, the level of aircraft noise was set as an objective variable, and gender, age, occupation. Education, the type of house, the structure of windows, the consciousness of settlement in the district, and the period of residence were set as explanatory variables. And the quantification theory I was applied to the analysis. The most influencing factor of the damage consciousness on aircraft noise was the education, the second occupation, the third age, the forth the consciousness of settlement, the fifth the period of residence, the sixth gender, the seventh the type of house, and the least influencing factor among them was the structure of windows. These findings will be a useful guideline when the government seeks to set up policies which will help solve the resident's noise problems near Taegu Airport.

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Ultrashort Optical Pulse Generation at 10 GHz by Pulse Compression of Actively Mode-Locked Fiber Laser Output (능동 모드잠금 광섬유 레이저 출력의 펄스 압축에 의한 10 GHz 극초단 광 펄스 발생)

  • Seo, Dong-Sun;Weiner, Andrew M.
    • Journal of IKEEE
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    • v.9 no.2 s.17
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    • pp.115-122
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    • 2005
  • We report 400 femto-second highly stable, nearly transform-limited, pulse generation at 10 GHz in $1540{\sim}1550$ nm wavelength region by adiabatic soliton pulse compression of an actively mode-locked fiber ring laser output. Without using any supermode selection device, supermode beating noise has been suppressed below -123 dB/Hz, resulting less than 100 femto-second timing jitters at the noise band of $1\;kHz{\sim}100\;MHz$.

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Control Method of the Clarity and the Period of the Beat in a Ring Structure (링 구조물의 맥놀이의 선명도와 주기 조절법)

  • Kim, S.H.;Cui, C.X.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.228-229
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    • 2008
  • In this study, we propose an effective method to improve the clarity and period of the beat in a ring structure. Ring is an simplified model of a Korean bell, in which beating vibration and sound are very important features. An equivalent ring theory is applied and finite element analysis on the equivalent ring is performed to determine the condition of the asymmetric element for the clear and proper period beat. The clarity and the period of the beat are improved by attacking asymmetric mass and decreasing local thickness. Using the equivalent ring, the amount and position of the local variation for the required beat condition are determined and the results are verified by experiment.

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