• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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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 $2\sim8dB$.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.9
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• pp.850-857
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• 2011

Generally, sound-absorbing materials in vehicles are used for giving the comfort to passengers by reducing noise while driving. Materials of which targets are light weight, high performance, eco friendliness and recycling have been developed recently. In this study, sound-absorbing materials using PET(polyethylene terephthalate) hollow fibers to achieve the light weight and the high sound absorption performance are developed, and then evaluated to meet a requirement for the automotive components. The test results show that the acoustic performances of developed products having new fiber structure are better than those of the conventional product.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.131-136
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• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The character and level of impact noise generated depends on the object striking the floor, on the basic structure of the floor, and on the floor covering. This study base on the evaluate of isolation performance of impact sound according to the impact noise reduction methods. Reduction methods consist of four ways. First way is increase thickness of bare floor and other ways are using the soft coverings on the floor and ceiling assembles. Last way is make floating floor with shock absorbing materials.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.9 s.90
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• pp.811-818
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• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The character and level of impact noise generated depends on the object striking the floor, on the basic structure of the floor, and on the floor covering. This study base on the evaluate of isolation performance of impact sound according to the impact noise reduction methods. Reduction methods consist of four ways. First way is increase thickness of bare floor and other ways are using the soft coverings on the floor and ceiling assembles. Last way is make floating floor with shock absorbing materials.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.198-203
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• 2001

This paper discusses an experimental method for measuring the insertion loss (IL) performance of a double panel that are used in vehicles. Instead of two adjacent reverberation chambers which are generally used to measure the transmission loss (TL) of the large sound isolation materials, air-borne sound insulation tester was utilized to determine the IL and articulation index (AI) of standardized deadening materials. In comparison to reverberation chamber method, air-borne sound insulation tester method is more space-saving, more time-saving and more simple to the automotive acoustics. From the empirical results, it is verified that the performance of deadening materials is closely connected with thickness of panels, type of filling material that is filled into a double panel, and area ratio of double panel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.97-102
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• 2004

The Characteristics of noise and vibration by heavy-weight floor impact sound was studied. Resonance frequency increased a little in structures that use damping material in living room and bedroom, and acceleration waves length that respond became short, and displayed aspect that oscillation level decreases. Result that measure sound pressure level, structure that compare and applies damping materials with structure that apply the resilient materials from 63Hz lower part that impact energy is concentrated in energy spectrum of heavy-weight floor impact sound displayed result that sound pressure, level decreases remarkably. Therefore, according to use of damping materials, confirmed reduction effect of heavy-weight floor impact sound.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.5
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.919-922
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• 2003

The correlation between noise and vibration by a heavy-weight floor impact was studied. The triggering technique was used for increasing the reliability and stability to measure the level of sound pressure, sound intensity and vibration acceleration. The simple finite element and rigid body analysis method were suggested to calculate the natural frequencies of the multi-layer floor system. The result show that the isolation material adapted to reduce the light-weight floor impact noise, causing the natural frequency lower, make resonance with dominant driving frequency, and increase the noise level very sharply. Therefore the noise level Peak in the region of low frequency, below 63Hz, would be related with the natural frequencies of the floor system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.414-422
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• 2013

As structure-borne sound, the floor impact sound is one of the serious noises in residential building. Most of heating system applied to the typical Korean residential building is floor heating system which is called ondol. The ondol usually consists of finishing material, mortar with heating coil, light-weight aerated concrete and reinforced concrete. This study focused on the isolation of heavy-weight impact sound and modification of mortar and light-weight aerated concrete. Specifically the glass foam aggregate was added on light-weight aerated concrete. Also, water-cement ratio and amount of cement on mortar were revised. The sound pressure level of heavy-weight impact was measured in reverberation chamber using both bang-machine and impact ball. The size of specimen was 1 m by 1 m. Substitution ratio of glass foam aggregate on light-weight aerated concrete shows relationship with heavy-weight impact sound pressure level. In addition, heavy-weight impact sound pressure level was decreased with increment of water-cement ratio and amount of cement on mortar.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.2
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• pp.21-34
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• 1988

Machinery enclosures are widely adopted to reduce the noise emission in various fields of application. Emitted noise, which is due to the vibration of enclosure's outer surface, is composed of two kinds of sound with different path of propagation. One is the "structure-borne sound", while the other is "air-borne sound". In order to get a most efficient machinery enclouser a prudent consideration upon the above structure-borne and air-borne sound is required, as the guiding principle of contermeasure for each noise is quite different. The controlling of input vibration and its isolation are major subjects for the structure-borne sound, and the specifications of absorbing members and damping panels are the major related matters for the air-borne sound. Hence, it seems very efficient to separate the total sounds into two categories with a great accuracy when one think of further reduction of noise from the existing enclosure, although its separating methods have not been made clear for many years. Author proposes an application method of experimental modal analysis to extract the structure-borne sound from the measured total radiation sound, as the air-borne sound is deduced by the vectorial difference between the measured total radiation sound and the calculated structure-borne sound. In order to calculate the correct structure-borne sound by the excitation at an arbitrary point on the enclosure structure, it is important to decide 1) how to estimate the enclosure's surface vibration velocity and 2) how to compute the radiation sound which is considered as the effect of vibration modes of enclosure surface. The former can be solved with total frequency response function calculated by the application of experimental modal analysis. The latter is to be solved by the author's new approaches for radiation sound computation by means of the Rayleigh's integral equation and the boundary-element method applied complex surface vibration velocity. As a first step, structure-borne sound by the excitation at an arbitry point on the rectangular plate with fixed edges, has been calculated to verified the reliability of the developed computation methods. The results of calculation show good agreements with those of the actual measurements.actual measurements.