임피던스법을 이용한 보이드 슬라브의 개선방안에 관한 연구

오재응,김영식 한국소음진동공학회 2001 소음 진동 Vol.11 No.2

In apartment buildings, floor-impact sound has been regarded as the major source that causes complaints from residents. It is mainly due to the use of light-weight structures and the lack of researches in terms of floor-impact sound. The purposes of this study are analyzing the characteristics of vibration response and sound radiation of 12type void slabs in the improvements void slab by impedance method and finding the fittest improvements void slab on the 12type void slab. The main results of this study are summarized as below: (1) In the $\frac{1}{3}$ octave band level of sound radiation, $\frac{1}{3}$ octave band levels, measured from four-divided improvement void slab(No.8) and eight-divided improvement void slab(No.12), are 10~25 dB lower than that of standard void slab(No.1) in the 1250 Hz. Especially, eight-divided improvement void slab(No.12) is the best void slab in terms of radiation efficiency of sound level. (2) In the correlation relation of acceleration and sound radiation, standard void slab(No.1), four-divided improvement void slab(No.8), SK standard four-hole void slab(No.10), and eight-divided improvement void slab(No.12) are positive correlation relation.

자동차 대시 구조의 소음진동 성능개선을 위한 단순 상사구조물의 소음방사성능 연구

임차섭(Lim, Cha-Sub),유지우(Yoo, Ji-Woo),박철민(Park, Chul-Min),조진호(Jo, Jin-Ho) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.10

A dash panel plays an important role to protect noise as well as heat. Meanwhile, it is also the most important path that transfers energy to the interior cavity, so that some of noises are transferred via air and its structural vibration becomes a major issue. From the viewpoint of NVH performance, simplified structures analogues to the dash wall are dealt with. Stiffeners, damping sheets and sound packages attached to a flat panel are taken into account as design variables. Structural radiation characteristics(thus, structure borne) such as radiation efficiency and radiation power are mainly discussed. For the case when an excitation is applied on a frame that surrounds the panel, it is shown that the radiation efficiency increases by attaching a stiffener to the panel, which is similarly found from the case when a panel is directly excited. It seems more effective to attach damping sheets along the boundary area of the panel rather than its middle area. The radiation efficiency of sound packages may make a dominant contribution to transmission loss as well as sound radiation. Experimental work was carried out to verify the results based on the simulation study.

선체 구성 강판의 종류 및 고유진동수를 고려한 선체의 음향방사효율 추정

한형석(HyungSuk Han),이경현(KyungHyun Lee),박성호(SungHo Park) 한국소음진동공학회 2013 한국소음진동공학회 논문집 Vol.23 No.12

The definition of the radiation efficiency is very important to estimated underwater radiated noise of a ship. Considering the structure of the ship, it can be found that the hull of a ship consists of a lot of plates supporting by longitudinal and transverse stiffener. Therefore, various modes of the hull vibration occur related to the combination of these plates including stiffeners. In this paper, the method to define the radiation efficiency is suggested considering the vibration mode of the hull based on Uchidas experimental equation of the radiation efficiency. The suggested method is verified by the experiments with various kinds of naval vessels.

수음실 내 구조체의 진동량 계측을 통한 바닥충격음레벨 예측

김명준,김흥식,김하근 한국소음진동공학회 2003 한국소음진동공학회 논문집 Vol.13 No.1

In an apartment building, the impact sound from upstairs has been regarded as a main source of noise causing discontentment among occupants. To set the optimum design for sound insulation. it is nesessary to suggest the useful tools or technique that predict the floor impact sound. The purpose of this study is to investigate the applicability of the theory of sound radiation. We measured the vibration acceleration levels on the interior structures and predicted the sound pressure level of the room by using them. The result show that the predicted value, in general, were in good agreement with the measured values within 5∼10% in error rate.

Study on the general characteristics of the sound radiation of a rectangular plate with different boundary edge conditions

유지우 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.5

Sound radiation is the most important phenomenon when a structure vibrates, which is strongly dependent on boundary conditions and its shape such as aspect ratio. This paper deals with general aspects of sound radiation from this viewpoint. A particular guided and pinned condition being taken into account here, is that the cross-modal terms can average out for all possible point excitation locations. Then, the average radiation efficiency based on the modal radiation efficiency and corresponding radiation power can numerically be obtained. It is shown that the radiation power of the guided plate is governed by the piston mode as well as the critical frequency. Unlike the pinned plate, no clear corner and edge mode regions below the critical frequency may be found for the guided case. Meanwhile, if the plate damping increases the similar tendency that the radiation efficiency increases below the critical frequency is found, as the vibrational level decreases. For the strip with a large aspect ratio, the radiation power is maximised at frequencies where the wavelength is an integer times the short edge length. This can be seen for both the guided and the pinned boundary conditions.

Specification of the hull vibration to control underwater radiated noise by estimation with modified experimental sound radiation efficiency

한형석,이경현 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.9

Underwater radiated noise is one of the most important performances related to the stealth of a naval vessel. However, the evaluationfrequently cannot be performed due to the problem of the test expense. The specification of the hull vibration is an effective method usedto specify the underwater radiated noise indirectly. Therefore, in order to specify hull vibration, the sound radiation efficiency should becorrectly determined. In this paper, the sound radiation efficiency which was modified with experimentally derived sound radiation efficiencyas well as Maidanik’s and Uchida’s sound radiation efficiency is suggested and verified through experiments. Based on the determinedsound radiation efficiency in this research, the specification of the hull vibration to satisfy with the limit of the underwater radiatednoise is suggested for a ship.

수조에서의 원통형 구조물 음향방사효율 측정

한승진(Seungjin Han),강명환(Myunghwan Kang),이종주(Jongju Lee),김현진(Hyunjin Kim),정현기(Hyungi Jung) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10

Underwater radiation noise is an important characteristic in the naval weapon system. In this study, acoustic radiation efficiency of a circular cylindrical structure is measured in the reverberant water tank. It is difficult to measure the radiation efficiency of underwater structure, such as UUV and weapons in real operation environment. Therefore, the structure is excited by interior-shakers and the vibration level and the acoustic radiation power of the structure is measured in the laboratory water tank. Reverberation time is measured and the acoustic radiation power is corrected by subtracting the reverberation sound power level from that measured directly. As a result, the acoustic radiation efficiency is calculated, and it can be used for predicting the underwater radiation noise and effectiveness of radiation reduction means.

선체진동 신호로부터 정의된 선체의 수중방사소음을 이용한 프로펠러 캐비테이션 소음 예측 연구

한형석(Hyungsuk Han),전수홍(Soohong Jeon),이청원(Chungwon Lee),김용훈(Yonghoon Kim) 한국소음진동공학회 2019 한국소음진동공학회 논문집 Vol.29 No.6

In order to estimate the underwater radiated noise of a ship, the underwater radiated sound from the hull as well as the propeller cavitation should first be defined. However, the propeller cavitation sound is not defined yet but the approximated value is used in the design state of the ship. In this research, the propeller sound including external flow-induced noise is defined. The underwater radiated noise of a ship and underwater radiated noise estimated from the acceleration on the hull by experiment.

Application of a wavenumber domain numerical method to the prediction of the radiation efficiency and sound transmission of complex extruded panels

Kim, Hyungjun,Ryue, Jungsoo,Thompson, David J.,Mü,ller, Angela D. Elsevier 2019 Journal of Sound and Vibration Vol.449 No.-

<P><B>Abstract</B></P> <P>Complex-shaped aluminium panels are adopted in many structures to make them lighter and stronger. The vibro-acoustic behaviour of these complex panels has been of interest for many years but conventional finite element and boundary element methods are not efficient in predicting their performance at higher frequencies. Where the cross-sectional properties of the panels are constant in one direction, which is the case for extruded panels, wavenumber domain numerical analysis can be applied and this becomes particularly suitable for panels with complex cross-sectional geometries. Because they are based on a two-dimensional model, these methods can reduce the computational cost compared with other numerical methods using full three-dimensional models, while nevertheless including three-dimensional effects. In this paper, a coupled waveguide finite element and boundary element method is applied to predict the radiation efficiency and sound transmission of a double-layered aluminium extruded panel from a train carriage floor. The results are interpreted in the wavenumber domain from which the contributions of different types of waves can be identified. In the calculations, the air cavities between top and bottom panels are considered to examine their contributions to the vibro-acoustic behaviour of the panel. The predicted results are compared with measured ones obtained using a finite length panel. To reflect the finite length of the actual panel used in the measurement, spatial window functions are applied to the sound transmission through the infinitely long panel, giving improved agreement with the measurements.</P>

상반성 기법과 p-p method를 이용한 구조물 방사소음 유한요소해석 기법 연구

유지우,박헌,이지운 한국음향학회 2023 韓國音響學會誌 Vol.42 No.1

구조진동 소음 문제의 평가에 있어 방사소음은 중요한 물리적 특성으로 음향 인텐시티 측정으로 확인이 가능하지만, 시간이 오래 걸리고 까다로운 측정 조건 때문에 시험을 꺼리는 경향이 많다. 그 대안으로 시뮬레이션이 사용되고 있으며, 그 정확도도 높다. 문제는 방사소음 파워와 방사효율 같은 중요한 물리량을 얻기 위해서는 이를 계산해 주는특정한 소프트웨어가 필요하다는 점이다. 본 연구에서는 이런 관점에서 일반적인 유한요소 해석 소프트웨어를 사용하여 방사소음 파워와 방사 효율을 계산하는 후처리 기법을 제안한다. 제안된 두가지 방법은 기본적으로 시험에서 사용하는 방법을 시뮬레이션에 활용하는 것이다. 첫번째 방법은 상반성 기법을 이용하는 것이며, 두번째 방법은 인접한 2 개의 위치에서 계산된 음압을 이용하는 방법이다. 두가지 방법이 모두 효과적으로 방사소음 파워를 예측할 수 있음을보였으며, 그 한계도 설명하였다.