• 한국소음진동공학회논문집
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• 제14권7호
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• pp.577-585
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• 2004

In this paper, reactive shearing structural intensity method is extended to damping patches placement on outer panels of outdoor unit of air-conditioner to reduce its structural borne noise. The structural intensity is calculated from the normal velocities of structures that are measured by using a laser scanning vibrometer, and $textsc{k}$-space (wave-number domain) signal processing is used to obtain the spatial derivatives in formulation of structural intensity. This method is applied to the outdoor unit of air-conditioner on shaker-exciting mode and operating mode. and then damping patches are placed over area of high reactive shearing structural intensity for reducing the radiated noise. Experimental results show the largest reduction of sound pressure level of an outdoor unit by appling small damping patches to optimal position.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.257-260
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• 2004

This study aims to evaluate factors of ceiling structure influencing to the floor impact sound. For this reasons, we measured the vibration of ceiling and the floor impact sound by ceiling structure. The main results from this study are that ceiling structure makes worse to non-ceiling structure for an effect of air layer in heavy-weight floor impact sound. But it has an effect on light-weight floor impact sound about $2\sim8dB$.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3197-3202
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• 2013

철도차량 차체 설계시 음압레벨에 따른 소음해석을 통한 차체 패널의 감쇠특성을 최적화하는 것이 필요하다. 본 논문은 철도차량 차체용 알루미늄 더블스킨 압출패널의 진동감쇠특성 해석을 통한 철도차량 차체의 구조소음 해석에 관한 연구이다. 주파수응답 가진시험을 통하여 측정된 기계적 모빌리티 값인 포인트 모빌리티, 트랜스퍼 모빌리티, 모달 모빌리티와 단순음원이론을 사용하여 정규화된 음압을 계산하였다. 도포용 감쇠재의 감쇠값을 라미네이티드 쉘요소에 사용하여 유한요소해석을 수행함으로써, 감쇠처리에 의한 소음감소수준 예측을 하였다. 또한 실제 차량 구조와 유사한 고정경계조건의 감쇠특성해석을 통하여 열차주행시 발생하는 진동의 영향을 크게 받는 언더프레임과 같은 부위에 일정 두께의 감쇠재 코팅이 진동 및 소음억제에 큰 효과가 있을 것으로 사료된다.

• 한국생산제조학회지
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• 제7권2호
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• pp.81-90
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• 1998

Noise produced by surface transportation vehicles affects our daily lives, penetrating wherver man lives or works. In this paper, a theoretical model has been studied to describe the sound radiation by the surface vibration of in-service tires and studied about an experiment on sound radiation characteristic due to tire vibration. When a tire is analyzed, it has been modeled as a curved beams with distributed sprongs and dash-pots which represent the radial, tangential stiffnes and damping of tire, respectively. The experimental investigation for the sound radiation of a radial tire has been made. Based on the sound intensity and STSF(Spatial Transformation of Sound Field) techniques. the sound pressure and the sound radiation are measured. The comparison of numerically analyzed results with experimental results was made seperately for the tire in rotation. As a result of this study, a program for the prediction of the tire vibration sound radiation was intended to by developed which enables a designer of a tire to foresee the influence of the various design factors on the tire vibration sound radiation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.96-99
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• 2005

Noise and vibration generated by heavy-weight floor impact in apartment buildings were studied. The resonance frequency increased in the floor structures where damping materials were used in the living room and the bedroom. Both the acceleration wavelength and the acceleration level decreased. The results showed that the resonance frequency increased and vibration acceleration level decreased when the damping materials were used. Heavy-weight impact sound levels of the structure decreased substantially below 80Hz.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.624-629
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• 2003

In this paper, broadband shunt technique for increasing transmission loss is experimentally investigated. Piezoelectric shunt damping is studied using resonant shunt circuit and negative capacitor shunt circuit. A resonant shunt circuit is implemented by using a resistor and inductor. Negative Capacitor shunt damping is similar in nature to resonant shunt damping techniques, as a single piezoelectric material is used to dampen multi-mode. Performance of both methods is experimentally studied for noise reduction. This is based upon SAE J1400 test method and a transmission loss measurement system is provided for it. This paper will present the test setup fer transmission loss measurement and the tuning procedure of shunt circuits. Finally the results of sound transmission tests will be shown.

• Journal of Advanced Marine Engineering and Technology
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• 제16권5호
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• pp.85-96
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• 1992

Engine enclosures are widely adopted to reduce the noise emission in various fields of application. The radiated noise, which is due to the vibration of enclosure's outer surface, is composed of two kinds of sound power with different path of propagation. One is the 'structure-borne sound power' which stems from the engine's vibratory force applied to the structure of enclosure through the mounting parts of engine etc., while the other is the 'air-borne sound power' which is originated by the sound power radiated from the engine surface to the inner space of enclosure that should excite the vibration of enclosure from inside. In order to get a most efficient engine enclosure is required a profound consideration upon the above structure-borne and air-borne noise, since the guiding principle of countermeasure for each noise is quite different. The controlling of input vibration and its isolation are major subject for the structure-borne sound power and the specifications of absorbing member and damping panels are the major interests for the air-borne sound power. Hence it seems very efficient to separate the total sound power into two categories with a great accuracy when one think of further reduction of engine noise from the exciting enclosure, however, its separating methods have not been made clear for many years. Then author proposes a new practical separation method of two propagation path's contribution to the total radiation sound power for the enclosure under the engine operating condition.

• 한국철도학회논문집
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• 제19권1호
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• pp.1-10
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• 2016

본 논문은 고속열차 객실 내 유리창의 차음 성능을 향상시키기 위한 기반연구로, 접합유리에 사용되는 고분자 필름의 물성과 음향학적 특성을 분석하여 그 상관관계를 살펴보고자 하였다. 기존에 사용되고 있는 PVB(polyvinyl butyal) 필름 및 다른 단량체 비율을 가지는 PVB 유도체, 그리고 유리 사이 차음재로 사용가능 한 PC(polycarbonate)의 동적기계적 특성을 분석(DMA)하였다. DMA 분석을 통해 상온에 가까운 온도범위에서 유리전이온도($T_g$)를 가지며 tan ${\delta}$(loss tangent) 값이 큰 것으로 나타난 PVB-HEMU 시편의 댐핑(damping) 성능이 가장 우수할 것으로 예측하고, 이를 고속철도 차량의 접합유리창과 동일한 구조에서의 투과손실 시험과 해석을 통해 검증하고자 하였다. 접합필름의 종류에 따른 유리창 투과손실 값을 투과손실 측정(인텐시티법)과 FE 해석을 이용해 도출하고, 고분자 필름의 물성과 음향성능 간 상관관계 분석을 위한 기초자료를 구축하였다.

• Elastomers and Composites
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• 제49권2호
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• pp.95-102
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• 2014

최근 공동주택의 층간 소음으로 인하여 사회적 문제가 크게 대두되고 있다. 본 연구에서는 소음 차단 성능을 향상시키기 위해 바닥 진동 제어 시스템에 적용되어질 방진고무를 제조하였다. 다양한 유형의 고무 중 우수한 노화특성, 낮은 반발탄성 및 높은 댐핑특성의 성질은 갖는 부틸 고무를 방진고무의 원료 고무로 선정하였다. 그리고 부틸 컴파운드에 첨가되는 카본블랙의 유형과 함량에 따른 방진고무의 물성을 확인하였다. 표면적이 큰 카본블랙을 사용하거나 함량이 증가할수록 고무와 카본블랙간의 결합고무의 함량이 증가하여 높은 기계적 물성, 낮은 반발탄성과 높은 댐핑특성을 나타내었다. 연구 결과를 토대로 최적의 카본블랙 종류와 함량을 결정하고 방진고무를 제조한 뒤 바닥진동제어 시스템에 적용하였다. 바닥충격음을 측정한 결과 경량충격음 40 dB, 중량충격음 43 dB을 나타내어 소음차단 성능이 우수한 것을 확인할 수 있었다.

• 소음진동
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• 제5권2호
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• pp.169-181
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• 1995

A theoretical model has been studied to describe the sound radiation analysis for structural vibration noise control of tire under the action of random moving line forces. When a tire is analyzed, it has been modeled as a curved beam with distributed springs and dash-pots which represent the radial, tangential stiffness and damping of tire, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y = 0 and to be axially infinite. The material of curved beam and elastic foundation are assumed to be lossless, and governed by the law of Bernoulli-Euler beam theory. The expression for sound power is integrated numerically and its results examined as a function of Mach number(M), wavenumber ratio(.gamma.) and stiffness factor(.PSI.). The experimental investigation for structural vibration noise of tire under the action of random moving line forces has been made. Based on the STSF(Spatial Transformation of Sound Field) techniques, the sound power and sound radiation are measured. The experimental results show that operating condition, material properties and design factors of the tire have a great effect on the sound power and sound radiation characteristics.