• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.175-180
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• 2006

The acoustical properties of multi-layered treatments of materials used in applications, such as automotive liners, generally cannot be directly measured by a one-time test in a standing wave duct. Therefore, we have to consider predicting them by the four-pole transfer matrix method. This method requires performing TCM or TLM for measuring the transfer matrix of each layer and calculating the total transfer matrix of the whole multi-layered material. The final predicted absorption ratios and transmission losses of the multi-layered treatments strongly depend on the measured transfer matrix of each layer. All these functions have been included in a new designed acoustical software.

• 한국소음진동공학회논문집
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• 제17권11호
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• pp.1013-1020
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• 2007

In this paper, the predictions and measurements of sound transmission loss(STL) are discussed for various types of acoustical materials and carpets. Random incidence sound transmission losses are measured by the sound intensity method. The in-house software HONUS2005 is used to predict TL and estimate the various physical properties such as the flow resistivity, the structure factor, the porosity, the Possion's ratio, and etc. After this estimation, various multi-layered materials with a steel plate are measured and predicted. In particular, Carpets are assumed to be membranes to predict acoustical performance. To confirm this assumption, double and triple-layered cases are also observed including two different kinds of carpets.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.309-314
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• 2007

Optimal layer sequencing of a multi-layered acoustical foam is solved to maximize its sound transmission loss. A foam consisting of air and poroelastic layers can be optimized when a limited amount of a poroelastic material is allowed. By formulating the sound transmission loss maximization problem as a one dimensional topology optimization problem, optimal layer sequencing and thickness were systematically found for several frequencies. For optimization, the transmission losses of air and poroelastic layers were calculated by the transfer matrix derived from Biot's theory. By interpolating five intrinsic parameters among several poroelastic material parameters, dear air-poroelastic layer distributions were obtained; no filtering or post-processing was necessary. The optimized foam layouts by the proposed method were shown to differ depending on the frequency of interest.

• 한국음향학회지
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• 제43권3호
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• pp.261-269
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• 2024

본 논문에서는 흡음형 소음기의 음향성능을 향상시키기 위해 다층 흡음재 배치 순서를 최적화하였다. 소음기의 음향성능은 투과손실로 판단하였으며, 투과손실을 계산하기 위해 유한요소법 기반 수치해석 프로그램을 사용하였다. 흡음재는 흡음형 소음기에서 많이 사용되는 다공탄성 물질인 폴리우레탄을 사용하였으며, 내부에 공기가 흐르는 상황을 가정하여 Biot-Allard 모델을 적용하였다. 2 kHz 대역까지 관심주파수 영역을 설정하여 흡음재가 단층으로 구성되어 있을 때 음향성능에 영향을 주는 물성치를 확인하였으며, 폴리우레탄 물성치를 바탕으로 단층 및 다층 흡음재를 가진 소음기의 음향성능을 서로 비교하였다. 이후 Nelder-Mead 방법을 적용하여 소음기 내 다층 흡음재의 배치 순서를 최적화하였으며, 단층 흡음형 소음기에 비해 평균 투과손실이 증가하는 것을 확인하였다.

• 한국음향학회지
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• 제41권4호
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• pp.375-388
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• 2022

본 논문은 다층 다공성 흡음재가 채워진 원통형 소음기의 음향투과손실을 구하는 과정을 다루었다. 다층다공성 흡음재 내부에서 전파되는 파동을 다루기 위해 Biot모델과 Johnson-Champoux-Allard-Lafarge(JCAL) 모델을 이용했다. 소음기 해석에 필요한 경계조건들을 얻었고 그것들을 토대로 수치적으로 모드를 구하는 과정을 설명했다. 얻은 모드들을 이용하여 2층 소음기에 대해 수치적인 실험을 진행했으며 처음 12개의 모드만으로도 음향투과손실이 수렴함을 보였다. 마지막으로 흡음재의 종류를 바꿔가면서 음향투과손실을 계산했고 이를 유한요소법을 이용한 결과와 비교함으로써 본 연구에서 제시한 모드 매칭법의 유효성을 검증했다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.309-313
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• 2000

A structural-acoustic coupling problem involving fluid in a cavity divided with flexible walls and porous materials is investigated in this paper. In many practical problems, the use of finite elements to discretize the fluid region leads to large stiffness and mass matrices. But, since the acoustic boundary element discretization requires to put elements only on the surface of structure, the size of matrices is reduced considerably. Here, we developed a numerical analysis program for the structural-acoustic coupling problems of the multi-region cavity, using boundary elements for the fluid regions and finite elements for the structure. By considering sound transmission through layered systems placed in a cavity, the accuracy of the coupled acoustical-structural finite element model has been verified by comparing its transmission loss predictions with analytical sloutions. Example problems are included to investigate the characteristics of the multi-region structural-acoustic coupling system with porous material.