• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.364-368
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• 2004

Micro Cellular Plastics create a sensation at polymer industrial for lowering product cost & overcoming a lowering of mechanical intensity. This research based on the experiment of sound absorption & transmission characteristics inquire into acoustic property of Micro Cellular Plastics. This experiment clarify the change of cell foaming rate for foaming time and the change of sound absorption & transmission for foaming rate.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.139-142
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• 2006

This paper describes a new method using random modulated strategies for switched reluctance machines. The proposed method is combined random turn-on, turn-off angle technique and random pulse width modulation technique. The purpose of this proposed method is to decrease harmonic spectrum, and thus reduce the emitted acoustical noise. A random generator is generated by linear congruential generator (LCG) using random pulse position (RPP) scheme. Simulation results show that the harmonic intensity of proposed method is better than that of conventional method.

• The Journal of the Acoustical Society of Korea
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• v.10 no.6
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• pp.82-100
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• 1991

본 연구에서는 회전톱날에서 발생하는 공기소음원 규명의 실현가능성을 검토하였다. 음향인텐시 티법은 3차원 선도, 인벤시티 벡터에너지선도, 동고선도 등의 표현에 유용한 장점을 갖고 있다. 근거리 음장 거동에 대한 추정, 주파수영역에서의 벡터 또는 스칼라 음향인텐시티는 소음원규명의목적으로 사 용되는 측정기법이다. 결과에 따르면 난류는 원형톱날의 이 부근에 나타나며, 톱날의 변동압력 측정에서 와류구조의 영향에 대한 근거는 측정된 음향인텐시티에 의해 도출된다. 도한 회전속도가 증가함에 딸k, 상호작용은 도플러현상을 일으키는 중요한 소음메타니즘이 될 수 있다.

• Journal of the Korean Society of Safety
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• v.17 no.1
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• pp.1-5
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• 2002

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.349-354
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• 2007

This paper considers acoustic analysis of silencer within a Dry vacuum pump. Main object is noise reduction of Dry Vacuum Pump using the silencer. First, we measured SPL and Intensity for noise source identification and then, designed for the silencer corresponding with noise character. 4-pole parameter are used for predicting transmission loss which is one of characteristics of silencer when we designed for silencer. Calculated Transmission Loss to change main effective factor and selected to optimal value using Design of Experiment. Finally, noise reduction is estimated to compare existing silencer with optimal silencer.

• The Journal of the Acoustical Society of Korea
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• v.24 no.1E
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• pp.1-6
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• 2005

The inner hair cell stereocilia of the guinea pig cochlea was examined under a scanning electron microscope (SEM) after loud tone exposure onto the ear drum of the animal. Before and after guinea pigs were exposed to intensive and continuous tone such as 106 dB SPL in intensity, the functioning of the cochlea was monitored by N1-N2 audiograms. The structural damage of the stereocilia of inner hair cells (IHCs) and outer hair cells (OHCs) was examined using the SEM in x 1500 magnification. The comparison between the functional change of the cochlea and the structural damage of the IHC stereocilia is done by means of photographic observation. It can be shown that the functional change might be related to the structural damage of the IHC stereocilia after intensive acoustic trauma.

• Speech Sciences
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• v.13 no.1
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• pp.55-66
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• 2006

A purpose of this study is to investigate the acoustic characteristics of English stress produced by the two groups of South Kyungsang (henceforth, SK) Korean speakers: high-proficiency and low-proficiency with reference to English native speakers. Another purpose is to compare results from the high- and low-proficiency SK Korean subjects with those of the native speakers, and to provide an analytical account of how approximate the high-proficiency SK Korean subjects' production is to the native speakers' and how different the low-proficiency SK Korean subjects' is from the native speakers'. Results indicated that the native speakers' main strategy used in producing stressed syllables was duration while the high-proficiency SK Korean subjects' was predominantly pitch-oriented. The low-proficiency SK Korean subjects' pitch patterns showed regularity, emphasizing the penultimate syllable with pitch. In comparing duration among the three groups, both groups of the SK Korean subjects became more even in their duration values for each syllable as the structure of the word or the sentence became more complex.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.201-204
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• 2006

In the side scan sonar method, use is made of the back-scattering, at low grazing angles of incidence to the seabed, of relatively high-frequency acoustic waves radiated in a fan-shaped beam from a transducer contained in a towed body. The fan beam is oriented so that the wider angle is in the vertical plane (scan range) and the narrower angle in the horizontal plane (beam width) with the axis of the beam normal to the ship track. The display of the returns is usually realized as a series of closely spaced intensity-modulated lines on a paper recorder or computer screen display. In this way a two-dimensional picture of the seabed is build up.

• Proceedings of the KSPS conference
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• 2003.10a
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• pp.43-49
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• 2003

This study reveals the perceptual role of stop release burst to Koreans' recognition of POA(place of articulation) and voicing in the English word-final stops. 10 Korean subjects participated in a perception experiment wherein the stimuli are prepared on the basis of the amount of acoustic information, which includes the release burst. The result shows that i) release burst plays an important role in the recognition of POA in the order of velar, alveolar, and bilabial stops, and ii) the release burst more enhances the correct recognition of voiceless stops than that of voiced stops. This result leads us to conclude that the role of stop release burst differs with respect to the POA and voicing of the stops, and it is possibly related to the different intensity of release in voicing and in each POA.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.170-172
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• 2007

The purpose of this study was to examine the syllable structures of ten Korean numeric sounds produced by ten subjects of the same age. Each sound was normalized and divided into onset, vowel, and coda sections. Then, acoustical measurements of each syllable were done to compare the ten sounds. Results showed that there was not much deviation from the grand average duration and intensity for the majority of the sounds except the two diphthongal sounds on which their boundary points varied among the speakers. Some syllable boundaries were quite obvious while others were ambiguous. There seemed some tradeoff among the syllable components depending on their acoustic features.