• 한국소음진동공학회논문집
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• 제19권5호
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• pp.439-446
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• 2009

Noise sources in electric machines are broadly categorized as magnetic, mechanical, electronic and aerodynamic. Especially, there are several kinds of noise sources due to the change of reluctance by rotor position in IPM motor. To separate acoustic noise by mechanical structure and electromagnetic sources, resonance frequency and the effect of vibration and acoustic noise by electromagnetic sources are analyzed. And then, the structural and electromagnetic designs to reduce acoustic noise are performed. The relevance about the study on noise reduction of IPM motor is verified by noise experiment, noise and vibration analysis.

• 한국소음진동공학회논문집
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• 제19권7호
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• pp.673-678
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• 2009

The efficiency of active sonar that is used underwater observation equipment is important for obtain the information of topography and trace for the objects. Sound wave transmitted from sonar are distorted by acoustic window which is to protect sonar. Making various sonar dome is impossible for experiment, because consumed unnecessary time and expense. So, the purpose of this study is to simulate and analyze the acoustic window propagated sound wave from sonar for designing model reduced insertion loss. Simulation is performed by transient analysis and fluid-structure interaction analysis. As a result, this study will give a opportunity for efficient design of sonar dome without high cost and time consumption.

• 로봇학회논문지
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• 제7권4호
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• pp.231-242
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• 2012

This paper proposes particle filter(PF) method using acoustic signal for localization of an underwater robot. The method uses time of arrival(TOA) or time difference of arrival(TDOA) of acoustic signals from beacons whose locations are known. An experiment in towing tank uses TOA information. Simulation uses TDOA information and it reveals dependency of the localization performance on the uncertainty of robot motion and senor data. Also, comparison of the PF method with the least squares method of spherical interpolation(SI) and spherical intersection(SX) is provided. Since PF uses TOA or TDOA which comes from measurement of external information as well as internal motion information, its estimation is more accurate and robust to the sensor and motion uncertainty than the least squares methods.

• 한국음향학회지
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• 제18권5호
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• pp.58-62
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• 1999

본 연구에서는 한국어 연결숫자인식에 있어서 모델간의 변별력을 향상시키기 위하여 음향학적 파라메터(Acoustic Parameter)를 사용하는 것을 제안한다. 제안된 방법은 음성학적 지식에 근거하여 적절한 주파수 대역별 에너지의 비의 로그값을 추가적인 특징 파라메터로 사용한다. 실험결과, 제안된 방법을 사용함으로써 기본 인식시스템에 비해 오류율이 최고 46% 정도 감소됨을 확인할 수 있었다. 그리고 채널보상 기술을 함께 적용함으로써 69% 정도의 오류율 감소를 얻었다.

• The Journal of the Acoustical Society of Korea
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• 제20권4E호
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• pp.17-23
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• 2001

To develop the code of predicting flow-field and aeroacoustic noise by an electrical cable, a combined CFD-Acoustic analogy approach is selected. The two dimensional, unsteady and incompressible Reynolds-averaged Navier-Stokes solver with κ-ω and κ-ω SST turbulence modeling is used to calculate the near flow-field around an electric cable. Near-field results are then coupled with two-dimensional Curle's integral formulation based upon Lighthill's acoustic analogy with the assumption of acoustic compactness. To validate this code, numerical results are compared with experimental data for a circular cylinder. The simulation shows an overprediction on acoustic amplitudes, but overally speaking, the spectrum pattern of sound pressure agrees well with experiment within an acceptable amount of error. In addition, a few cross-sections of the cable were selected and tested with each other in terms of drag and radiated noise

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.206-211
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• 2008

Noise sources in electric machines are broadly categorized as magnetic, mechanical, electronic and aerodynamic. Especially, there are several kinds of noise sources due to the change of reluctance by rotor position in IPM motor. To separate acoustic noise by mechanical structure and electromagnetic sources, resonance frequency and the effect of vibration and acoustic noise by electromagnetic sources are analyzed. And then, the structural and electromagnetic designs to reduce acoustic noise are performed. The relevance about the study on noise reduction of IPM motor is verified by noise experiment, noise and vibration analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.212-217
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• 2008

Acoustic noises generated during motor operation in mechanical system are from electromagnetic, mechanical, aerodynamic, and electrical sources. For identification of mechanical noise origins, misalignment, unbalance, fan shape, resonance, and vibration modes have been extensively considered to describe noise behavior. An experiment-based approach as well as a mathematical approach needs to be adopted for a realistic study into noise and vibration of the motor, because motor noise characteristics differ from type to type due to various noise sources. In this paper, a brushless DC motor for air-conditioner fan is analyzed by finite element method to identify noise source, and the analysis results are verified by experiments, and sensitivity analysis is performed by design of experiments.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.76-79
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• 2004

Dynamic oscillation motion of a pendant drop has been Investigated experimentally when acoustic wave is applied. This problem is of particular interest in the understanding of transport phenomena, accompanied by liquid drop. In this experiment, pendant drop was made to oscillate by inducing the acoustic wave and the subsequent drop motion was recorded by a high-speed camera. The results obtained indicate that liquid drop hanging on the flat surface has resonant frequencies on each shape oscillation modes. It is also found that exists the swing mode of oscillation on the pendant drop.

• 대한음성학회지:말소리
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• 제59호
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• pp.1-11
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• 2006

This study was designed to investigate the relationship between intelligibility and phonemic contrasts, and acoustic features in terms of speech development. A total of 212 Putonghua speaking children was participated in the experiment. There were phonemic contrasts significantly related with speech intelligibility: aspirated vs. fricative, retroflex vs. unretroflex, and front vs. back nasal vowel contrast. A regression analysis showed that 88% of the speech intelligibility could be predicted by these phonemic contrasts. Acoustic values were significantly related to the intelligibility of the Putonghua-speaking children's speech: voice onset time of unaspirated stops, and the duration of frication noise in fricatives.

• 소음진동
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• 제9권3호
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• pp.565-569
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• 1999

Recently, fiber optic hydrophone is a subject which has attracted as a underwater acoustic sensor. In this study, Finite element modeling of fiber optic hydrophone for hollow cylindrical mandrel was performed and the acoustic sensitivity was calculated to estimate the performance of single element fiber optic hydrophone. And acoustic sensitivity was measured in acoustic water tank to verify the result of simulation. The result of FE analysis and experiment is -126 dB re rad/$\mu$ Pa and -128 dB re rad/$\mu$ Pa respectively.