• MALSORI
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• no.64
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• pp.1-14
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• 2007

The purpose of this study was to examine the acoustic perception different by formants change for profoundly hearing impaired children with cochlear implants. The subjects were 10 children after 15 months of experience with the implant and mean of their chronological age was 8.4 years and Standard deviation was 2.9 years. The ability of auditory perception was assessed using acoustic-synthetic vowels. The acoustic-synthetic vowel was combined with F1, F2, and F3 into a vowel and produced 42 synthetic sound, using Speech GUI(Graphic User Interface) program. The data was deal with clustering analysis and on-line analytical processing for perception ability of acoustic synthetic vowel. The results showed that auditory perception scores of acoustic-synthetic vowels for cochlear implanted children were increased in F2 synthetic vowels compaire to those of F1. And it was found that they perceived the differences of vowels in terms of distance rates between F1 and F2 in specific vowel.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.182-195
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• 1998

The relation between the vibration induced from machinery and the radiated sound is complicated. Acoustic intensity method is widely used to obtain the accuracy of noise identification. In this study, as groundwork, the complex acoustic intensity method is performed to identify noise source and transmission path on different free space point source fields. From the numerical analysis for these simple fields, it is possible to predict the sound field characteristics which noise sources are related with each other, and certificate the validity of complex acoustic intensity. As an industrial application, the complex acoustic intensity method is applied a diesel engine to identify sound radiation characteristics in the near field.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.22 no.4
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• pp.98-103
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• 1986

The passive acoustic system only has generally used in fish detection. But the passive acoustic system has not been tried in fishing since Freytag has proposed a possibilities of the passive detection of fishes in 1963. This paper describes the .feasible aspects of fish detection by listening of the sound they make. The passive acoustic system accompanied the active acoustic system may expand the range of detection and compensate for lack of capabilities each other, but there are some difficulties in noise rejection because the fre9uency range of ship noises covers the whole range vf biological sounds. The attempt to collect useful informations from underwater would be greatly contributed in fisheries.

• Journal of the Korean Society of Combustion
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• v.23 no.1
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• pp.13-20
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• 2018

Transverse acoustic mode in annular combustion chambers affects air-fuel mixing characteristics in the nozzle and can result in heat release fluctuations in the combustor. In addition, the acoustic mode coupling between the nozzle and the combustion chamber is one of the key parameters determining combustion instability phenomenon in the annular combustor. In this study, acoustic coupling between the nozzle and annular combustor was numerically analyzed using 3D-based in house FEM code. As a result, it was found that the acoustic mode inside the combustion chamber at anti-node locations of the transverse mode was strongly influenced by the nozzle inlet boundary conditions.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.481-488
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• 2018

This study suggest the improvement of the CFRP adhesive mixing ratio about acoustic window to enhance SONAR performance. The CFRP of submarine is produced by allocation an acoustic window zone by the beam width of SONAR sensors. During the sea trial, SONAR system's bearing and range accuracy data is not in tolerance due to debonding phenomenon on CFRP. The inappropriate mixing ratio of adhesives caused that peeling phenomenon occurred in the acoustic window part, which is the reason for the deterioration of SONAR sensors performance. The report includes explanation of test procedure of SONAR, root cause analysis, CFRP manufacturing procedure, laboratory tests results, and proof of the performance at the sea trial.

• Speech Sciences
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• v.14 no.4
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• pp.221-232
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• 2007

Topiramate (TPM) is a new antiepileptic drug characterized by a clinical effective reduction in seizure frequency and it represents a useful drug effective in a wide range of epileptic patients. Known side effects are represented by weight loss, hypohidrosis, anorexia, sedation, nephrolithiasis, cognitive complaints and language disorders. This study is to examine acoustic characteristics of patients with TPM. 15 patients were assessed through a Computerized Speech Lab (CSL) applied before the beginning of therapy with TPM and 3 months after medication had been stabilized. Tests had been chosen to assess voice onset time (VOT), total duration (TD), vowel formants, loudness, pitch, speaking rate, and articulation patterns. We compared the data from patients and healthy volunteers. The statistical analysis of the results did not show changes in acoustic tests, except for TD which was increased. The increase of the TD is evaluated as a deterioration of fluency. Our results suggest that patients with TPM did not experience acoustic speech changes except that fluency was declined. Unlike previous studies, the medication of TPM has nothing to do with speech problems in patients with epilepsy.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.763-766
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• 2002

A BEM is highly efficient method in the sense of economic computation. However, boundary integration is not easy for the complex and moving surface e.g. in a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element depending on its acoustic characteristics. In this study, an axial fan is assumed to have loading noise as a dominant source. Dipole sources can be computed based on the FW-H equation. Acoustic field is then computed by changing Kirchhoff surface on which near-field is implemented, to analyze the effect of Kirchhoff surface on it.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.863-869
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• 2009

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. This paper analyzes noise characteristics of a brushless DC motor for air-conditioner fan, and proves that the test motor noise originates from acoustic modes of airspace in the motor. The motor noise sensitivity analysis by design of experiments reveals that the noise characteristics are closely related to switching frequency and frame thickness.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.1
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• pp.63-71
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• 1987

The measuring of acoustic intensity has been investigated by many researchers and practicians during the last several decades. But due to the lack of measurement accuracy, they have had no practical use. In recent years, the two microphone acoustic intensity method has been developed by the advancement of FFT analysis technique and the digital data processing equipment. This new method of using two microphones gives informations on the noise source survey and the acoustic power of sound radiation source without the anechoic room. In this paper, theoretical formulae for the two microphone acoustic intensity method and the sound transmission loss are checked. The obtained results for the acoustical enclosure of gas heat pump were compared with the classical field incidence mass law. The surface vibration modes for a panel of enclosure were also estimated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.772-777
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• 2002

A BEM is highly efficient method in the sense of economic computation. However, boundary integration is not easy for the complex and moving surface e.g. in a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element depending on its acoustic characteristics. In this study, an axial fan is assumed to have loading noise as a dominant source. Dipole sources can be computed based on the FW-H equation. Acoustic field is then computed by changing Kirchhoff surfaces on which near-field is implemented, to analyze the effect of Kirchhoff surface on it.