• 대한후두음성언어의학회지
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• 제8권2호
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• pp.178-184
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• 1997

Vocal nodule due to vocal hyperfunction is one of the representative chronic diseases of vocal folds, and it can be cured by surgical movement, and/or voice therapy. The present study is, focusing on the latter, to compare the acoustic and aerodynamic results of the pretreatment with those of posttreatment, and then to investigate the objective date on the efficiency of the voice therapy for the patients with vocal nodules. 11 females(age : 7-49) and 5 males(age : 8-40), total 16 patients wi vocal nodules treated by voice therapy were participated as subjects. Six measurements and comparisons of pretreatment and posttreatment of the results were performed : litter, shimmer, and noise-to-harmonic ratio as acoustic analyses ; maximum phonation time, mean flow rate, and the subtraction of mean flow rate from maximum flow rate as aerodynamic analyses. As a result, 14 of 16 subjects showed improvement at more than 4 of 6 measurements, and in group data, every measurements of posttreatment was improved significantly than the pretreatment. On the whole, the improvement of aerodynamic aspects was more statistically significant than that of acoustic ones.

• 수산해양기술연구
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• 제29권4호
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• pp.292-300
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• 1993

Acoustical imaging has made brilliant progress in the medical science field, and has also made much progress in the nondestructive testing and under water acoustics applications since doctor Dussik brother has studied about possibilities of making images of brain by recording variations in the intensity of ultrasonic beam from head in 1937. In this paper an acoustical image is reconstructed with the power spectra analysed by impulse ultrasound wave generated by electrodynamic transducer(EDT). The EDT generates the impulse ultrasound of 77KHz in center frequency and 120KHz in bandwidth at -20dB by 1200V exciter in this experiment. The impulse ultrasound has the dominant frequency components of 47KHz, 177KHz, 110KHz and 155KHz. The U shape object is adopted in making an acoustical image. The resulted spectral acoustical images are different from the optical view of the U shape object. However the image reconstructed from 110KHz spectrum is very similar to the original optical shape of the object. Even KHz level impulse sound of 70$\mu$sec pulse width is found to be useful in reconstructing acoustical imaging improvement.

• 융합신호처리학회논문지
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• 제8권1호
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• pp.32-38
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• 2007

강의실에서의 환경조건을 확립하기 위해 PA(Public-Address)를 사용한 경우와 PA를 사용하지 않은 경우의 두 가지 패턴으로 임펄스 응답을 측정하였다. 측정결과에 의해 음성 명료도에 관련된 음향물리지표를 계산하고 PA 유무에 의한 각 지표의 차이를 검토하였다. 그리고 임펄스 응답을 이용하여 4연속 음절 명료도 시험을 하여 잔향에 따른 PA사용이 어느 정도 음성 듣기를 향상시키고 있는가도 검토하였다. 그 결과, 잔향이 어느 정도 적은 경우에는 PA에 의한 음압레벨의 향상이 충분한 명료도의 개선이 되는 가능성이 있으나 잔향이 긴 경우에는 제시 음압레벨을 높여도 PA 시스템에서는 명료도의 개선이 기여되지 않는다는 것을 알 수 있었다.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2008년도 춘계학술발표대회 논문집
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• pp.436-440
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• 2008

Among those various facilities attached to the school building, the Auditorium is being utilized for not only the Exercise Activity but also for many purposes such as Culture, Public Performance, Education, Assembly and so on. In order to utilize in maximum such function of the multipurpose auditorium, an adequate acoustic design with regard to the Clarity of Voice and Music in accordance with its use-purpose should be accompanied. However, as the most part of multipurpose auditoriums is designed with high ceiling-height by its peculiar character, and due to use of the material of strong reflexibility, it is appearing the defect that excessively exposes the reverberation of sound. In order to make out an optimal acoustic condition within the broad space such as an auditorium, the acoustic characteristics must be considered from the planning stage, however in the most case, those acoustic problems are being settled through the repair works after construction. On such viewpoint, this Study intends to analyze the room acoustic characteristics from the planning stage using a computer simulation based on the blueprint of multipurpose auditorium in S High School located in Gwangju. It is considered that the material analyzed in such way could be practically applied as a fundamental material enables to improve the acoustic capability when a similar broad space is planned hereafter.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2008년도 춘계학술발표대회 논문집
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• pp.272-275
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• 2008

In case a middle school music room locating in Iksan City, this space had been finished its construction work with the indiscreet sound-absorbing materials despite the music lesson is taught thereat. Accordingly, when music lesson since it sounds aridly due to insufficiency of echo and sound-volume feeling in music appreciation or music performance sound, there is some difficulty in the music lesson. For the purpose to control the obstructive factors owing to such short Reverberation Time, it optimizes the acoustic factor using Acoustic Simulation after arrangement of Acoustic Design, it has conducted a Psycho-acoustics Experiment using the Auralizational Technique that can experience the Virtual Acoustic Field at its designing stage. As the result of investigation about the acoustic satisfaction on the relevant subject space and the satisfaction with regard to the pertinent each items, it was known that the valuation on acoustic performance was evidently improved at 'after-reformation' than 'before-reformation'. It is considered that such material could be utilized as the useful material that can improve the architectural acoustic factor when construction and renovation of any middle school music room in the future.

• 한국분무공학회지
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• 제10권3호
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• pp.29-37
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• 2005

The spray and acoustic characteristics of a gas/liquid swirl coaxial injector are studied experimentally. The self-pulsation is defined as a pressure and flow rate oscillations by a time-delayed feedback between liquid and gas phase. Self-pulsation has strong influences on atomization and mixing processes and accompanies painful screams. So. the spray and acoustic characteristics are investigated. Spray patterns are observed by shadow photography technique in order to determine the onset of self-pulsation. And self-pulsation boundary with Injection conditions and recess length is get. To measure the frequency of the spray oscillation. oscillation of the laser intensity which passes through spray is analyzed by Fast Fourier Transform. For acoustic tests, a PULSE System was used. Acoustic characteristics of a swirl coaxial injector are investigated according to the injection conditions. such as the pressure drop or the liquid and gas phase. and injector geometries. such as recess length and gap size between the inner and outer injector. Front the experimental results. the increase of recess length leads to the rapid increase of the sound pressure level. And as the pressure drop of the liquid phase increases. the frequency of the self?pulsation shifts to the higher frequency. The frequency of spray oscillations is the same as that of the acoustic fields by self-pulsation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.13-16
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• 2007

반파장 공명기가 장착된 연소실의 비선형 음향 감쇠를 알아보기 위하여 비선형 음향해석을 수행하였다. 먼저 공명기가 없는 기본 연소실에 80 dB에서 150 dB의 넓은 범위의 음향파를 가진하여 음향장을 분석하였다. 제 1 접선방향 음향 모드의 감쇠율은 가진되는 음향파의 크기에 따라 비선형적으로 증가하였고, 125 dB 이상부터 비선형성이 나타나기 시작했다. 다음으로 반파장 공명기의 감쇠 효과를 조사하였다. 선형해석으로부터 유도된 최적의 음향학적인 동조 조건이 비선형 음향해석에서도 여전히 유효함을 알 수 있었다. 큰 음향파의 섭동에 대한 감쇠는 효과적이지만, 선형 음향 가진에 비해서 음향학적인 감쇠기로써의 기능은 작아짐을 알 수 있었다.

• 대한조선학회논문집
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• 제29권1호
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• pp.113-122
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• 1992

선박소음을 예측하는 과정중에서 고체소음 전달해석은 직접적으로 예측결과의 정도에 영향을 미치고 있다. 이에 대한 계산 방법으로서 경험식이 그 간편성 때문에 자주 사용되고 있지만 자체의 한계성 때문에 이론적 해석방법(Wave guide theory, SEA등)들에 대한 연구가 선박음향학 분야에서 꾸준히 수행되어 왔다. 본 연구에서는 SEA를 이용하여 22개의 plate로 구성된 선체구조의 단순모델을 대상으로 고체소음 전달손실에 대한 이론적 계산 및 실험적 산정을 수행하였다. 계산치와 실험치의 비교결과는 3 dB이내의 좋은 일치를 보여 주었다.

• The Journal of the Acoustical Society of Korea
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• 제22권4E호
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• pp.183-196
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curl's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method penn its generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 소음진동
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• 제4권2호
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• pp.231-238
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• 1994

This paper presents an experimental method to find the vibrational transmission characteristics of structures by using the structural intensity method which is used as the important techniques of active vibration control method. Experimental results are obtained from measurements performed on a structure beam by 2, 3 and 4 position linear accelerometr array (2, 3 and 4 structural intensity : 2, 3 and 4 S.I.) methods at near and farfield conditions. These results are compared with the measurement values of conventional power flow measurement method called input power measurement in order to verify the accuracy of structural intensity methods. To minimize the errors associated with 2, 3 and 4 S.I. methods, the measurement locations were selected by the result of modal analysis and the averaged data by the inter-change of accelerometer array was utilized. In 3 and 4 S.I. methods measured wavenumber instead of theoretical wavenumber was used. This paper shows that measurements of bending wave power flow by using 2, 3 and 4 S.I. methods can give accurate values under general field conditions in structural beam and the accuracy of 2, 3 S.I. methods is higher than 4 S.I. methods. Finally, 2 position linear accelerometer array method is suggested as the practical structural intensity technique.