• Science of Emotion and Sensibility
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• v.1 no.2
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• pp.133-147
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• 1998

이 글은 영구의 자동차내부 소음연구와 보버르트(Bobbert)의 첫 번재 독일어로 쓰인 연구를 다루고 있다. 승용차내부소음은 높은 적외파음향(infra sound)으로 특징지어 진다. 그런 까닭으로 그러한 종류의 소음을 A-평가계측(A-rated measurement)으로 그 영향을 파알하는 것은 한계가 있다. 자동차음향공학은 특히 인공청각(artificial head)기술의 발전, 소리의 합성적 제조 및 다양한 자동차 내부 음색(timbre)에 대한 일본연구가들 (하쉬모토, 쿠와노, 남바)에 의해 상당산 성취를 경험하였다. 위의 연구들은 무엇보다도 의미분별기법(Semantic Differentials)과 다차원측정방법(Multidimen-sional Scaling)을 사용하고 있다. 그러한 기법의 사용은 심리측정방법을 심리음향학(Psycho-acoustics), 특히 츠뷔커학파(Zwicker school)의 심리음향학 방법론과 결합한 것으로 볼 수 있다.

• The Journal of the Acoustical Society of Korea
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• v.17 no.6
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• pp.54-61
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• 1998

중주파수대역은 내부 음향 모드의 공명 및 모드간 상호 간섭 특성을 완전히 무시할 수는 없으나 모드 밀도가 비교적 높기 때문에, 기존의 저주파수용 모드기법이나 고주파수에 대한 통계적 및 기하학적 해석방법과는 다른 기법이 필요한 구간이다. 본 논문에서는 위상 을 포함한 기하음향모델을 이용하여 중주파수 특성을 고려하는 개념을 이용하여 해석기법을 확립하였으며, 삼각형빔법을 기초로 한 모델링을 하였다. 세 개의 서로 다른 특성을 지닌 대 상 공간에 대해 음향 경계요소법 및 실험에 의한 음향 주파수응답함수와 본 연구 결과를 비 교함으로써 유효성과 오차특성을 검토하였다. 이로부터 위상으로 고려한 중주파수 대역에 잘 적용될 수 있음을 확인하였고, Schroeder의 차단주파수 이하의 저주파수에서는 내부구조 에 의한 회절이, 차단주파수의 네 배 이상인 고주파수에서는 벽면에서의 산란이 간섭현상과 함께 고려되어야 함을 보였다. 이러한 해석기법은 중주파수대역에 있어서 청감특성을 고려 한 내부공간의 음향설계에 매우 유용할 것으로 사료된다.

• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.257-263
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• 2015

Acoustic identification of inner materials in a single-layer cylindrical shell is investigated with acoustic resonance theory. The theoretical resonance peak frequencies for a cylindrical shell are little affected by the density variation, but remarkably changed by the sound speed variation of inner materials. Such acoustic dependency can be utilized to identify inner materials in a cylindrical shell. Acoustic resonance spectrogram for a single-layer cylindrical shell is theoretically plotted as functions of normalized frequency and sound speed of inner materials. The inner materials can be acoustically identified by overlapping acoustic resonance peaks from measured backscattering sound field on the spectrogram. To experimentally confirm this method, backscattering sound field of cylindrical shell filled with water, oil or ethylene glycol was measured in water tank. The inner materials could be identified by acoustic resonance peaks of the backscattering sound field monostatically measured with a transduce of 1.05 MHz center frequency.

• The Journal of the Acoustical Society of Korea
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• v.29 no.3
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• pp.173-183
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• 2010

In this paper, acoustic transmission characteristics are theoretically considered on a cylindrical cavity system. The cylindrical cavity system is a simplified model of the acoustic cavity of King Seongdeok Divine Bell and it consists of a main cavity, a gap and an auxiliary cavity, Under a point sound source in the main cavity, acoustic frequency response property is determined and acoustic modes are analysed. The results are compared with those by the boundary element analysis using SYSNOISE. Using the proposed theoretical method, the effect of the auxiliary cavity and the gap on the resonance frequency and sound transmission characteristics is identified. Finally the best combination of the auxiliary cavity and gap is determined for the maximum transmission of the source frequency.

• The Journal of the Acoustical Society of Korea
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• v.9 no.3
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• pp.66-74
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• 1990

• The Journal of the Acoustical Society of Korea
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• v.12 no.3
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• pp.76-82
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• 1993

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.46-52
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• 2000

Internal waves existing in the stratified ocean significantly affect acoustic propagation. In order to understand the effects of internal waves on acoustic propagation, the sound speed fluctuations due to internal waves are generated based on the Garrett-Munk spectrum which is derived from measured data in the East Sea. The acoustic propagation, where internal waves are present, is simulated numerically using a Galerkin higher order parabolic equation method(SNUPE). These results show favorable comparison to in-situ acoustic propagation data from the East Sea. To investigate the effects of acoustic propagation in random media, scintillation index is adopted and comparison between the measured and numerically simulated data is made.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.44-52
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• 1996

Acoustical characteristics of internal pipe structures and a loudspeaker of the thermoacoustic refrigerator are analyzed by using the transfer matrix method. The resonator system is dismantled into verious basic acoustic elements, and then linearized transfer matrices are serially combined with the dynamical system of linearized loudspeaker model, that the total system of thermoacoustic refrigerator can be analyzed in terms of frequency characteristics and acoustic field shape. Additionally, by using equations for energy flow through the capillary stack, the temperature distribution over the stack is numerically estimated. After expressing the acoustic work flow, thermoacoustic flow, and energy loss per unit length in a single capillary duct by using the transverse functional variations, overall energy flow rate and energy balance are obtained for the whole capillary stack. The final expression for energy flow through the stack is numerically evaluated by varying physical parameters obtained from the sound field analysis. After confirming good agreements between predicted and experimental results for the interior sound field of a refrigerator model, the thermoacoustic characteristics of Hofler's apparatus is analyzed by the proposed method and it is observed that the results agree well with Hofler's experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.780-788
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• 2009

AE technique was applied to the static structural test of the composite wing structure to evaluate the structural integrity and damage. During the test, strain and displacements measurement technique were used to figure out for static structural strength. AE parameter analysis and source location technique were used to evaluate the internal damage and find out damage source location. Design limit load test, the 1st and 2nd design ultimate load tests and fracture test were performed. Main AE source was detected by an sensor attached on skin near by front lug. Especially, at the 1st design ultimate test, strain and displacements results didn't show internal damage but AE signal presented a phenomenon that the internal damage was formed. At the fracture test, AE activities were very lively, and strain and displacements results showed a tendency that the load path was changed by severe damage. The internal damage initiation load and location were accurately evaluated during the static structural test using AE technique. It is certified from this paper that AE technique is useful technique for evaluation of internal damage at static structural strength test.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.142-150
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• 2012

The waveguide finite element (WFE) method is a useful numerical technique to investigate wave propagation along waveguide structures which have uniform cross-sections along the length direction ('x' direction). In the present paper, the vibration and radiated noise of the submerged pipe with fluid is investigated numerically by coupling waveguide finite elements and wavenumber boundary elements. The pipe and internal fluid are modelled with waveguide finite elements and the external fluid with wavenumber boundary elements which are fully coupled. In order to examine this model, the point mobility, dispersion curves and radiated power are calculated and compared for several different coupling conditions between the pipe and internal/external fluids.