• Title/Summary/Keyword: Acoustic Problem

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Vibro-acoustic Analysis of Simplified Satellite Model by Using the Statistical Energy Analysis (단순화된 위성체의 통계적 에너지 해석법을 이용한 음향-진동 연성 해석)

  • C. H. Jeong;J. G. Ih;S. M. Moon;Kim, H. B.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.371.1-371
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    • 2002
  • At lift-off, the jet noise of launch vehicle produces a severe acoustic environment and the loads induced by the acoustic pressure may be damaging to paylaod and equipments. Prediction of the acoustic environment is needed to support the design and test-qualification of components. Currently, such a high frequency problem is usually dealt with by using the SEA, of which the assumptions match reasonably well with the vibro-acoustic condition of system. (omitted)

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A study on wideband underwater acoustic signal amplifier design for generating multi-frequency (다중 주파수 재생을 위한 광대역 수중 음향 신호 증폭기 설계 연구)

  • Lee, Dong-Hun;Yoo, Seung-Jin;Kim, Hyeong-Moon;Kim, Hyoung-Nam
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.3
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    • pp.179-185
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    • 2017
  • The problem that occurred in the design/fabrication/testing of the wideband transmitting power amplifier for an embedded active SONAR (Sound Navigation and Ranging) system operating underwater was analyzed and the solution of the problem was proposed in this paper. Wideband acoustic SONAR systems had been developed in order to improve the underwater detection performance. The underwater acoustic transmission system had been also developed to achieve the wideband SONAR system. In this paper, the wideband acoustic transmission signal was generated using a 2 Level sawtooth type Class D PWM (Pulse Width Modulation) which was not complicated to implement. When the sonar signals having two or more frequencies were simultaneously generated, parasitic frequencies were added to the original signals by integer multiples of the frequency difference of the original signal. To cope with this problem, we proposed a way to remove the parasitic frequency from the source signal through modeling and simulation of the implemented power amplifier and PWM control hardware using MATLAB and Simulink.

Acoustic Analysis of KSR-III Combustion Chamber with Various 5-Blade Baffles under Non-Reacting Condition (5-블레이드 배플이 설치된 로켓엔진 연소실에서의 상온음향 해석)

  • Kim, Hong-Jip;Kim, Seong-Ku;Sohn, Chae-Hoon
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.167-171
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    • 2003
  • Acoustic characteristics of baffled combustion chamber to elucidate suppressing effect of baffle on combustion instability are numerically investigated by linear acoustic analysis. A hub-blade baffle of 5 blades is selected as a candidate one and five variants of baffles with various configuration are designed. Resonant-frequency shift and damping factor are analyzed quantitatively as damping parameters. When the hub is located radially at the pressure node, the decrease of resonant frequency and increase of damping factor in 1R mode are dominant. But sub-1T mode is formed within hub, therefore, there would be a possibility of initiating 1T mode in unbaffled region, which would occur another problem. For smaller hub size, four kinds of axial baffle length is selected. As the axial baffle length increases, resonant frequency shift and increase of damping factor of transverse acoustic modes is obtained. Especially, two close acoustic modes such as 1L and 1T could be overlapped for a certain axial length, resulting in extreme increase of damping factor. The present study based on linear acoustic analysis is expected to be a useful confirming tool to predict acoustic field and design a passive control devices such as baffle and acoustic cavity.

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Vibro-acoustic Analysis of Simplified Satellite Model by Using the Statistical Energy Analysis Technique (단순화된 위성체의 통계적 에너지 해석법을 이용한 음향-진동 연성 해석)

  • Jeong, Cheol-Ho;Ih, Jeong-Guon;Moon, Sang-Moo;Kim, Hong-Bae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.711-714
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    • 2002
  • At the lift-off condition, the combustion and Jet noise of launch vehicle produces a severe acoustic environment and the acoustic loads may be damaging to paylaod and equipments. Prediction of the acoustic environment is thus needed to support the load-resistive design and test-qualification of components. Currently, such a high frequency problem is usually dealt with by using the SEA technique, for which the assumptions should match reasonably well with the vibro-acoustic condition of system. The subsystems of SEA model was composed of 16 flat plates, 8 L-shaped beams, and 2 acoustic cavities. The frequency range was 400 Hz - 4 kHz considering the modal parameter. The experiment was performed in a high intensity acoustic chamber, in which the diffuse acoustic field was assured. By comparing the SEA analysis and the experiments, the error less than 5 dB was observed.

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Identification on Principle of Acoustic Wave Propagation in a Gas Duct (가스 파이프 내부의 음향 전파 특성에 관한 연구)

  • Kim, Min-Soo;Lee, Sang-Kwon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.1100-1105
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    • 2007
  • In the gas supply duct, the gas leakage caused by the impact of the construct equipment is serious problem. The identification of the impact position is an important issue and an engineering work. For the basic research of this problem, the principle studies for the acoustic wave propagation in a gas duct are proceeded in this paper. This principal work is based on the identification of the cut-off frequency associated with major modes of the gas duct theoretically and experimentally. The cut-off frequency is confirmed by STFT and cross-correlation function is used to identify the leakage position.

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차실 내부소음의 특성과 저감에 관한 실험적 고찰(상)

  • 정주화
    • Journal of the korean Society of Automotive Engineers
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    • v.5 no.2
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    • pp.15-20
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    • 1983
  • The nature and the sources of sound in cars is discussed in the light of many previous works, and the importance of the system resonances inside cars is suggested. An investigation of a 'boom' problem in a small size passenger car is described. It was established that the 'boom' frequencies coincided with engine firing frequency and also with several system resonances. To find out main transmission path of the noise to the car interior, various possible sources were eliminated from the investigation by means of simple modification to the vehicle. Data on the structural modes of the body, and the acoustic modes of the passenger compartment at various forcing cases were obtained to provide better understanding of the problem. It was found that the acoustic resonance responsible for the boom was controlled largely the bending motion of the floor. To investigate the effect of the structural modification to the acoustic response, center floor of the car was reinforced. a great reduction of the noise inside the car especially at the offending speed range, was achieved by this modification.

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Temperature Measurement of Silicon Wafers Using Phase Estimation of Acoustic Wave (음향파의 위상 추정을 이용한 실리콘 웨이퍼의 온도 측정)

  • Joonhyuk Kang;Lee, Seokwon
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.11
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    • pp.493-495
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    • 2003
  • Accurate temperature measurement is a key factor to implement the rapid thermal processing(RTP). A temperature estimation method using acoustic wave has been proposed to overcome the inaccuracy and contamination problem of the previous methods. The proposed method, however, may suffer from the offset and low resolution problem since it is implemented in the time domain. This paper presents a temperature estimation method using the phase detection of acoustic wave. Based on the frequency domain approach, the proposed technique increases the resolution of the measured temperature and reduces the effect of noise. We investigate the performance of the proposed method via experiments.

A Method to Manipulate Sound Power within a Selected Region Using Source Array (스피커 어레이를 사용한 공간의 음향 파워 제어 방법)

  • 최정우;김양한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.278-281
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    • 2004
  • Multiple sound sources are controlled to enhance sound power within a zone of interest. The problem of enhancing acoustic variable can be regarded as an optimization problem, which seeks an optimal control input that maximizes the acoustic variable. It should be noted that enhancing sound power of a selected region requires both the magnitude and direction to be controlled. For this reason, two kinds of cost functions that can represent the spatially distributed intensity are defined. Theoretical formulation shows the possibility of sound power control in a zone, and the detailed procedures of the proposed method are validated by numerical simulations.

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Development of articulatory estimation model using deep neural network (심층신경망을 이용한 조음 예측 모형 개발)

  • You, Heejo;Yang, Hyungwon;Kang, Jaekoo;Cho, Youngsun;Hwang, Sung Hah;Hong, Yeonjung;Cho, Yejin;Kim, Seohyun;Nam, Hosung
    • Phonetics and Speech Sciences
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    • v.8 no.3
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    • pp.31-38
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    • 2016
  • Speech inversion (acoustic-to-articulatory mapping) is not a trivial problem, despite the importance, due to the highly non-linear and non-unique nature. This study aimed to investigate the performance of Deep Neural Network (DNN) compared to that of traditional Artificial Neural Network (ANN) to address the problem. The Wisconsin X-ray Microbeam Database was employed and the acoustic signal and articulatory pellet information were the input and output in the models. Results showed that the performance of ANN deteriorated as the number of hidden layers increased. In contrast, DNN showed lower and more stable RMS even up to 10 deep hidden layers, suggesting that DNN is capable of learning acoustic-articulatory inversion mapping more efficiently than ANN.

Derivation of Acoustic Target Strength Equation Considering Pulse Type of Acoustic Signal (펄스 타입의 음향신호를 고려한 음향표적강도 이론식 개발)

  • Kim, Ki-June;Hong, Suk-Yoon;Kwon, Hyun-Wung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.812-819
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    • 2007
  • Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. This research provides the time pattern of TS in time domain, which is applicable to pulse modulated acoustic pressure field. If the time pattern of TS is predicted by using TS equation in frequency domain, it takes long time and difficult since time function pulsed acoustic wave may be decomposed into their frequency domain components. But TS equation in time domain has a convenience. If the expression for pulsed acoustic field has been obtained, the problem can be solved. Furthermore this paper introduces about mathematical equivalence quantities between EM wave and Acoustic Wave.

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