• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.204-209
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• 2004

Recently, the various performances of vehicle are rapidly improved. Therefore tire noise is recognized as important noise source because vehicle noise is considerably reduced. This study is performed for the control of the cavity resonance noise that is structure-borne noise, due to fluid(air)-structure interaction. For this investigation, FRF analysis has been carried out using FEM and we found an important factor affecting cavity resonance. The effect of this factor is confirmed by objective noise test. We confirmed that the result of FRF analysis and objective noise test is that the structure control of tire sidewall can reduce cavity resonance noise due to fluid-structure interaction

• 한국항행학회논문지
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• 제27권5호
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• pp.587-593
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• 2023

본 논문에서는 비행체 내부배선 복사내성 특성 해석 및 개선 대책을 위한 효율적인 설계 방안을 제안한다. 비행체 성능향상을 위한 탑재장비의 종류 및 밀도가 크게 증가하면서 내부 배선의 역할도 매우 중요해지고 있다. 특히, 배선 경량화 및 유연성 증가 요구가 커짐에 따라서 내부 배선 쉴드 구조의 사용이 어려워지고 이에 따라서 쉴드 구조 이외의 방법으로 복사내성 특성을 개선할 필요가 있다. 본 논문에서는 내부 배선 복사내성 특성에 큰 영향을 미치는 캐비티 공진을 회피하고 억제하여 복사내성 특성을 개선 할 수 있는 해석적 기법 기반 설계 방안을 제시한다. 시뮬레이션 예시 구조를 통해서 제안 방안의 효율성과 정확성을 검증하였다. 제안하는 방안은 기존 설계 방안 대비 99.6 %의 설계 시간 단축을 달성했다. 이를 통해서 내부 배선 복사내성 대책을 위한 초기 설계나 최적화 설계에 매우 유용하게 활용될 수 있다.

• 대한기계학회논문집A
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• 제28권2호
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• pp.118-124
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• 2004

The objective of the paper is to demonstrate the noise reduction characteristics of an air-gap resonator, which is composed of an air gap and a partition sheet. By means of installing the air-gap resonator in an enclosed cavity, acoustic resonance can be effectively suppressed using a small space. In particular, it is revealed from a simple, one-dimensional model that the air-gap resonator serves as the Helmholtz resonator that generally absorbs acoustic resonance energy at its resonance frequency. As a result, the air-8ap resonator also has a resonance frequency, which can be predicted with a simple frequency equation derived in the paper. Finally, verification experiments show that the air-gap resonator can be effectively designed by predicting a reasonable gap thickness using the simple frequency-equation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.202-207
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• 2003

In the paper, the noise reduction characteristics of a double-gap resonator, which is installed inside an enclosed cavity and is composed of two air-gaps and two partition sheets, are introduced by theoretical analyses and experimets. Analysis for a simple, theoretical model reveals that the double-gap resonator is more effective than the single-gap resonator that consists of an air-gap and a partition sheet, in that the former requires a smaller space than the latter. Furthermore, this theoretical conclusion is verified by comparison experiments using an actually manufactured enclosed cavity, of which the boundary surfaces are made of thick, stiff panels that can be assumed as rigid walls.

• Wind and Structures
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• 제13권4호
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• pp.363-374
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• 2010

Appropriate scaling methods for wind tunnel modelling of building internal pressures induced through a dominant opening were investigated. In particular, model cavity volume distortion and geometric scaling of the opening details were studied. It was found that while model volume distortion may be used to scale down buildings for wind tunnel studies on internal pressure, the implementation of the added volume must be done with care so as not to create two cavity resonance systems. Incorrect scaling of opening details was also found to generate incorrect internal pressure characteristics. Furthermore, the effective air slug or jet was found to be longer when the opening was near a floor or sidewall as evidenced by somewhat lower Helmholtz frequencies. It is also shown that tangential flow excitation of Helmholtz resonance for off-centre openings in normal flow is also possible.

• International Journal of Safety
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• 제5권1호
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• pp.17-23
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• 2006

An investigation was carried out to determine the effect of the thickness of the air-gap installed between the roof metal sheet and the headliner on booming noise in passenger cars. In addition, a way of offering quieter driving condition to drivers and passengers was studied. It was found that a very thin air-gap corresponding to approximately 3/100 of the height of the passenger compartment causes noticeable change in the coupled resonance frequencies and acoustic responses. Furthermore, a guideline is proposed for determining an optimal air-gap thickness during design stage of the air-gap beneath the roof metal sheet for reducing booming noise.

• 방재기술
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• 통권21호
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• pp.5-12
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• 1996

An experimental investigation has been made with the objcetive of studying the effects of air entrainment of fire strength. A rich jet flame is considered as an fire, and fire, and the air entrainment is controlled by introducing the tone excitation which is generated by means of a loudspeaker-driven cavity. The excitation frequency is chosen for the resonant frequency identified as a pipe resonance due to acoustic excitation. As the excitation intensity increases, the amplitude of oscillating velocity for inducing air entrainment is increased, the flame height decreased and the structure of diffusion flame gradually transformed to that of premixed flame.

• 한국전자파학회논문지
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• 제10권3호
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• pp.351-358
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• 1999

본 논문에서는 유전체가 삽입된 원통형 공진기에서 공진주파수들의 모드를 구분하는 방법에 대하여 기술한다. 공진주파수들의 모드를 구분하기 위해 먼저 빈 원통형 공진기에서 계산된 공진주파수와 EM 시뮬레이터인 Microstripes의 시뮬레이션 결과 값을 비교하였다. TE 모드는 가계를 z방향으로 여기시켰을 때, TM 모드는 자계를 ∮방향으로 여기시킨 경우와 비교하여 구분할 수 있었다. 가운데 유전체가 삽입된 원통형 공진기에 이 결과를 적용해 실험결과와 비교하여 모드를 구분하였다. 이 방법이 올바른 지를 확인하기 위해 유전체의 높이를 변화시키며 모드 추적을 하였다. TE011 모드는 공진주파수의 변화가 커서 다른 공진모드와 순서가 바뀌었으나, TE111 모드와 TE211 모드는 공진주수의 변화가 적었다.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1223-1229
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• 2007

Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the leading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

• 한국음향학회지
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• 제26권1호
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• pp.1-7
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• 2007

본 논문에서는 여름철마다 소음으로 사회적인 문제가 되고 있는 말매미 노랫소리의 음향특성과 발음 메커니즘을 연구하였다. 자연 상태에서의 노랫소리를 대상으로 파형과 FFT를 분석하였으며, 고속사진촬영으로 진동막 운동 형태를 분석하였다. 수컷 말매미의 복부 공동 (Cavity)의 공진주파수를 알기 위해 강제 공진 실험을 실시하였다. 실험 결과, 말매미의 두 진동막은 시간적으로나 형태적으로 비대칭 운동을 하며 매 진동시마다 다양한 주파수가 발생하는 것으로 관찰되었다. 또한 말매미는 약 $7{\sim}7.5 kHz$ 영역의 소리를 공명시킬 수 있는 구조를 갖는 것으로 확인되었다.