• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.197-202
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• 2001

The compressor is one of major noise sources in air conditioner outdoor units, especially deteriorating the sound quality. Therefore, the sound insulation materials layered with sound absorption materials are applied around compressors. In this study, the performance of the sound insulators is examined by measuring the insertion losses in power base and the effects of sound absorption materials, method of application and the shape of the insulators are also investigated. The importance of minimizing the opening is revealed well.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1269-1280
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• 2009

This study was performed to construct sound performance DB of royal palace buildings and to examine the special quality more scientifically. Research target of royal palace were Changdeokgung and Gyeongbokgung. Sound insulation performance between the adjacent room and facade, room acoustics of Pyeonjeon and Chimjeon which is representative building in royal palace were examined through field measurement. Measured values of RT($T_{mf}$) at Pyeonjeon were 0.78 sec. and 1.03 sec. in Seonjeongjoen and Sajeongjoen, respectively. The RTs of both Pyeonjeon buildings were estimated suitable for speech and lecture considering their volume. The RT($T_{mf}$)s at Chimjeon were measured in range of 0.29~0.55 sec. This meant that the acoustic energy in rooms was decreased by sound transmission through mulberry paper(Hanji) of traditional windows and doors. As a sound insulation performance, the single-number quantities($D_{ls,2m,nT,w}$) of the building facades in Pyeonjeon and Chimjeon were measured 4~20 dB. Also the single-number quantities($D_{p,w}$) between the adjacent rooms in Chimjeon were measured 3~18 dB. Sound insulation performance of traditional building elements such as window and door depended strongly on their layers and area.

• Advanced Composite Materials
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• v.17 no.1
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• pp.25-40
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• 2008

The research and development in soundproof materials for preventing noise have attracted great attention due to their social impact. Noise insulation materials are especially important in the field of soundproofing. Since the insulation ability of most materials follows a mass rule, the heavy weight materials like concrete, lead and steel board are mainly used in the current noise insulation materials. To overcome some weak points in these materials, fiber reinforced composite materials with lightweight and other high performance characteristics are now being used. In this paper, innovative insulation sheet materials with carbon and/or glass fabrics and nano-silica hybrid PU resin are developed. The parameters related to sound performance, such as materials and fabric texture in base fabric, hybrid method of resin, size of silica particle and so on, are investigated. At the same time, the wave analysis code (PZFlex) is used to simulate some of experimental results. As a result, it is found that both bundle density and fabric texture in the base fabrics play an important role on the soundproof performance. Compared with the effect of base fabrics, the transmission loss in sheet materials increased more than 10 dB even though the thickness of the sample was only about 0.7 mm. The results show different values of transmission loss factor when the diameters of silica particles in coating materials changed. It is understood that the effect of the soundproof performance is different due to the change of hybrid method and the size of silica particles. Fillers occupying appropriate positions and with optimum size may achieve a better effect in soundproof performance. The effect of the particle content on the soundproof performance is confirmed, but there is a limit for the addition of the fillers. The optimization of silica content for the improvement of the sound insulation effect is important. It is observed that nano-particles will have better effect on the high soundproof performance. The sound insulation effect has been understood through a comparison between the experimental and analytical results. It is confirmed that the time-domain finite wave analysis (PZFlex) is effective for the prediction and design of soundproof performance materials. Both experimental and analytical results indicate that the developed materials have advantages in lightweight, flexibility, other mechanical properties and excellent soundproof performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1038-1042
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• 2007

The factors influencing the floor impact sound insulation include floor finishing materials, shock absorbing floors (slabs included), and ceiling structures. The ceilings of the apartment houses, currently built in Korea, are set up with lower parts of slabs and paper finishing, or with double floors for protecting against floor impact sounds in order to improve the sound insulating performance. The most common the method of ceiling structure construction consists of 'wood boarded frames + Gypsum boards + ceiling papers', which is called the wood boarded frame method. This study aimed to measures and evaluates floor impact sound insulation by which the ceiling space are widened according to suppression system is added in apartment house ceiling structure.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.996-999
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• 2010

Aluminium extruded panel is the most important element for sound insulation in a express train. However, comparing with the flat plate with the same weight, the extruded panel shows remarkably low sound transmission loss above the 1st local resonance frequency, which is determined by the dimension of the core structure. Preceding study showed the possibility of the improvement of sound insulation performance by properly designing the core dimension. By the proper core design, local resonance frequency shifts to higher frequency region without any reduction of bending or torsional strength and without any weight increase. Based upon this result, this study investigates in detail the design modification of the core structure of the aluminium extruded panel used in a express train under development, in aspect of sound insulation. Design result is compared with those of other developed models.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.756-759
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• 2003

It is increasing the interest on the comfortable dwelling environment and the efforts to solve the problem of the floor impact noise in apartment houses have been realized, as a result numerous products have been made. The purpose of this study is to investigate the sound insulation performances according to foaming rate of floor impact noise insulators and flooring coverings in Mock-up Test Room. The test results of impact insulation performance for each floor impact noise insulators is that double structure of insulator is excel than one in low-middle frequency band and as foaming rate go up, the sound insulation performance is improved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1061-1066
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• 2016

Corrugation of a corrugated panel dramatically increases the bending stiffness per weight. However, corrugated panels show lower sound insulation performance than that of the flat plate having the same weight. Especially, in a particular frequency region, the sound transmission loss significantly decreases. Main reason of the problem is known as the local resonance. A number of local resonance modes occur above a certain frequency band and modal density rapidly increases. In this study, we investigate the relation of the sound transmission loss and the modal density. Finally, we propose a design methodology in terms of the modal density to improve the sound insulation performance of the corrugated panels without weight increase.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.143-148
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• 2007

This study examines the influence factor of flanking noise in the wall. Generally, there is the difference of airborne sound isolation between laboratory and field test. The purpose of this study is examing the cause of droping sound insulation performance in the field and searching the method of improving sound insulation performance. First, we measured the sound isolation in the wall at the lab. Then, we measured it in the field and compared them. At the base of these datum, we measured the flanking noise and solid transmission. For the flanking noise in the wall, we used intensive method. So, we found the influence of solid transmission.

• KIEAE Journal
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• v.12 no.1
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• pp.73-81
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• 2012

Floor impact sound has been most annoying for years among the noises which are produced in apartment. This study aims to analyze the improvement of floor impact sound by comparing the results of the test which was carried out for the wall slab type apartment and moment frame apartment, and also for the effect of advanced vibration isolation layer. Moment frame structure that main structure consists of column and slab has shown better performance for the heavyweight impact sound comparing with wall slab type structure which is general type in Korea. Stiffness of floor system was raised by reinforcing the stiffness of vibration isolation layer, and it was analyzed how much the floor impact sound performance was improved. The result showed that the reinforced floor had better performance than the existing floor system that uses lightweight porous concrete as vibration isolation material. In addition, a system used wire mesh in mortar showed improvement of floor impact sound than a system without wire mesh, and better performance for the frequency bands lower than 160 Hz which causes floor impact problem in wall slab type apartment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.672-676
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• 2010

In a railway vehicle, corrugated steel panel is widely used for the floor structure because of its high bending stiffness and light weight. However, this panel shows lower sound insulation performance than that of the flat plate with the same weight. Especially, in a particular frequency region, transmission loss(TL) rapidly decreases and it results in the deterioration of sound insulation performance of the overall floor structure. This study identifies that the severe decrease in TL is caused from the local resonance of the periodic corrugated structure. TL decrease by local resonance is investigated by experiment and finite element analysis. Finally, design modification of the corrugation is proposed to improve TL and the effect is verified by experiment.