• 제목/요약/키워드: Tone noise

검색결과 238건 처리시간 0.026초

Aeroacoustic Computation of Cavity Flow in Self-Sustained Oscillations

  • Koh, Sung-Ryong;Yong Cho;Young J. Moon
    • Journal of Mechanical Science and Technology
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    • 제17권4호
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    • pp.590-598
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    • 2003
  • A computational aero-acoustic (CAA) method is used to predict the tonal noise generated from a cavity of automobile door seals or gaps at low flow Mach numbers (A$\_$$\infty$/=0.077 and 0.147) In the present method, the acoustically perturbed Euler equations are solved with the acoustic source term obtained from the unsteady incompressible Navier-Stokes calculations of the cavity flow in self-sustained oscillations. The aerodynamic and acoustic fields are computed for the Reynolds numbers based on the displacement thickness, Re$\_$$\delta$*/=850 and 1620 and their fundamental mode characteristics are investigated. The present method is also verified with the experimentally measured sound pressure level (SPL) spectra.

A Study on the Characteristics of Sound Source of Hydrodynamic proceeding Bearings (유체 윤활 저널베어링의 음원 특성에 관한 연구)

  • Rho, Byoung-Hoo;Kim, Kyung-Woong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 한국윤활학회 2002년도 제35회 춘계학술대회
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    • pp.156-161
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    • 2002
  • Results of theoretical investigations on acoustical properties of hydrodynamic proceeding bearings are presented. Nonlinear analysis of rotor bearing system including rotor imbalance is performed in order to obtain acoustical properties of hydrodynamic proceeding bearings. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties of hydrodynamic proceeding bearings are identified through frequency analysis of pressure fluctuation calculated from the nonlinear transient analysis. The results show that the acoustical frequency spectra of hydrodynamic proceeding bearings are pure tone spectra, containing the frequency of the shaft rotation and its super-harmonics. The analysis also shows that the super-harmonics are predominant at neighborhood of the fluid film reformation and rupture regions.

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Facial Regions Detection Using the Color and Shape Information in Color Still Images (컬러 정지 영상에서 색상과 모양 정보를 이용한 얼굴 영역 검출)

  • 김영길;한재혁;안재형
    • Journal of Korea Multimedia Society
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    • 제4권1호
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    • pp.67-74
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    • 2001
  • In this paper, we propose a face detection algorithm using the color and shape information in color still images. The proposed algorithm is only applied to chrominance components(Cb and Cr) in order to reduce the variations of lighting condition in YCbCr color space. Input image is segmented by pixels with skin-tone color and then the segmented mage follows the morphological filtering an geometric correction to eliminate noise and simplify the segmented regions in facial candidate regions. Multiple facial regions in input images can be isolated by connected component labeling. Moreover tilting facial regions can be detected by extraction of second moment-based ellipse features.

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Matched Field Processing: Ocean Experimental Data Analysis Using Feature Extraction Method (실 해상 실험 데이터를 이용한 정합장 처리에서의 특성치 추출 기법 분석)

  • Kim Kyung Seop;Seong Woo Jae;Song Hee Chun
    • The Journal of the Acoustical Society of Korea
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    • 제24권1E호
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    • pp.21-27
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    • 2005
  • Environmental mismatch has been one of important issues discussed in matched field processing for underwater source detection problem. To overcome this mismatch many algorithms professing robustness have been suggested. Feature extraction method (FEM) [Seong and Byun, IEEE Journal of Oceanic Engineering, 27(3), 642-652 (2002)] is one of robust matched field processing algorithms, which is based on the eigenvector estimation. Excluding eigenvectors of replica covariance matrix corresponding to large eigenvalues and forming an incoherent subspace of the replica field, the processor is formulated similarly to MUSIC algorithm. In this paper, by using the ocean experimental data, processing results of FEM and MVDR with white noise constraint (WNC) are presented for two levels of multi-tone source. Analysis of eigen-space of CSDM and FEM performance are also presented.

Face Detection Using Color Information (색상 정보를 이용한 얼굴 영역 추출)

  • 장선아;유지상
    • The Journal of Korean Institute of Communications and Information Sciences
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    • 제25권6B호
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    • pp.1012-1020
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    • 2000
  • In this paper, This paper presents a new algorithm which is used for detecting and extracting human masks from a color still image. The regions where each pixel has a value of skin-color were extracted from the Cb and Cr images, after the tone of the color image is converted to YCbCr from. A morphological filter is used to eliminate noise in the resulting image. By scanning it in horizontal and vertical ways under ways under threshold value, first candidate section is chosen. If it is not a face, secondary candidate section is taken and is divided into two candidate sections. The proposed algorithm is not affected by the variation of illuminations, because it uses only Cb and Cr components in YCbCr color format. Moreover, the face recognition was possible regardless of the degree of shifting face, changed shape, various sizes of the face, and the quality of image.

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Single-bias GaAs MMIC single-ended mixer for cellular phone application (Cellular phone용 단일 전원 MMIC single-ended 주파수 혼합기 개발)

  • 강현일;이상은;오재응;오승건;곽명현;마동성
    • Journal of the Korean Institute of Telematics and Electronics D
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    • 제34D권10호
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    • pp.14-23
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    • 1997
  • An MMIC downconverting mixer for cellular phone application has been successfully developed using an MMIC process including $1 \mu\textrm{m}$ ion implanted gaAs MESFET and passive lumped elements consisting of spiral inductor, $Si_3N_4$ MIM capacitor and NiCr resistor. The configuration of the mixer presented in this paper is single-ended dual-gate FET mixer with common-source self-bias circuits for single power supply operation. The dimension of the fabricated circuit is $1.4 mm \times 1.03 mm $ including all input matching circuits and a mixing circuit. The conversion gian and noise figure of the mixer at LO powr of 0 dBm are 5.5dB and 19dB, respectively. The two-tone IM3 characteristics are also measured, showing -60dBc at RF power of -30dBm. Allisolations between each port show better than 20dB.

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A Study on the Characteristics of Sound Source of Hydrodynamic Journal Bearings (유체 윤활 저널 베어링의 음원 특성에 관한 연구)

  • Rho, Byoung-Hoo;Kim, Kyung-Woong
    • Tribology and Lubricants
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    • 제18권5호
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    • pp.333-338
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    • 2002
  • Results of theoretical investigations on acoustical properties of hydrodynamic journal bearings are presented. Nonlinear analysis including rotor imbalance is performed for a rotor-bearing system in order to obtain acoustical properties of hydrodynamic journal bearings. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties of hydrodynamic journal bearings are identified through frequency analysis of oil pressure fluctuation calculated from the nonlinear transient analysis. The results show that the acoustical frequency spectra of the fluid film are pure tone spectra, containing the frequency of the shaft rotation and its super-harmonics. The analysis also shows that super-harmonics are predominant at the neighborhood of the fluid film reformation and rupture regions.

Recognition of the Direct and Reflected Sounds in an Irregulary Formed Chamber (비정방형실내에서의 직접음과 반사음 식별에 관한 연구)

  • 차일환;박규태;임광호
    • The Journal of the Acoustical Society of Korea
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    • 제2권1호
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    • pp.11-19
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    • 1983
  • An irregulary formed chamber was designed and constructed to recognize the direct sound radiated from the sound source and the reflected sound from the walls of the chamber. The sound signal used was tone burst in the frequency response characteristics with the signal detection after transient effect. The direct wave, transient phenomena and the primary reflected sound could be asiily distinguished each other by measurements of the arrival time of the time difference. And also noise could be easily distinguished by the same method. The result obtained can be used in industries for automatic measurement of the sound pressure reponse characteristics with respect to frequencies.

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A study on the realization of color printed material check using Error Back-Propagation rule (오류 역전파법으로구현한 컬러 인쇄물 검사에 관한 연구)

  • 한희석;이규영
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 한국퍼지및지능시스템학회 1998년도 추계학술대회 학술발표 논문집
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    • pp.560-567
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    • 1998
  • This paper concerned about a imputed color printed material image in camera to decrease noise and distortion by processing median filtering with input image to identical condition. Also this paper proposed the way of compares a normal printed material with an abnormal printed material color tone with trained a learning of the error back-propagation to block classification by extracting five place from identical block(3${\times}$3) of color printed material R, G, B value. As a representative algorithm of multi-layer perceptron the error Back-propagation technique used to solve complex problems. However, the Error Back-propagation is algorithm which basically used a gradient descent method which can be converged to local minimum and the Back Propagation train include problems, and that may converge in a local minimum rather than get a global minimum. The network structure appropriate for a given problem. In this paper, a good result is obtained by improve initial condition and adjust th number of hidden layer to solve the problem of real time process, learning and train.

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Coded Performance of FH/BFSK Communication Systems with Partical Band Jamming (부분대역 재밍 신호하에서 부호화된 FH/BFSK 통신 시스팀의 성능)

  • 박상규
    • The Journal of Korean Institute of Communications and Information Sciences
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    • 제17권8호
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    • pp.837-845
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    • 1992
  • This paper shows the performance of FH /BFSK communication systems under worst case Jamming interference. The channel Is modeled with ratio-threshold technique, and as a lamming signal the tone Jamming and Gaussian Jamming are used. The performance is analyzed by using the channel capacity which is the code rate and bit signal-to-Jammer ratio, and we show that the performance degration becomes large as background noise Is big and obtain the best performance when the threshold level f is about 1.5.

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