• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.653-658
• /
• 2001

In this study, a new practical method of predicting the sound absorption coefficient for multiple perforated-plate sound absorbing system was developed using transfer matrix method. In order to validate the proposed method, the absorption coefficients calculated by transfer matrix method for single perforated plate were first compared with the absorption coefficients measured by SWR method according to different porosity, hole diameter, and thickness of the perforated plate. Based on the comparison results, transfer matrix method was further applied to double and triple perforated plates to evaluate the absorption coefficients. The experimental results showed that the absorption coefficients from transfer matrix method generally agreed well with the corresponding absorption coefficients from SWR method. However, due to the limitations of the impedance model used in this study, the measured values were differed with the calculated values for small porosity, hole diameter, and thickness in size of the perforated plate indicating the need of impedance model development for multiple perforated-plate sound absorbing system covering wide ranges of porosity, hole diameter, and thickness of the perforated plate.

• Journal of the Korean Society for Railway
• /
• v.12 no.5
• /
• pp.806-810
• /
• 2009

The air conditioner system that is used in large structure, such as hospital, hotel, railway platform and train generate a high level noise generally. A chamber with sound absorbing materials, such as glass wool and polyurethane foam, are installed in this system to reduce the noise. However, these chambers cause environmental problems owing to the sound absorbing materials recently. Therefore, we develop noise chamber a built-in perforated panel resonance system as eco-friendly chamber to solve this problems. This noise chambers show the same noise reduction performance as the current chambers in the range above 500Hz. But, it reduces the noise up to 8dB(A) comparison to the current chambers in the range 200Hz~400Hz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.519-520
• /
• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.527-528
• /
• 2010

Previous experimental results performed by many researchers for a couple of decades in South Korea have shown that an absorbing sheet inserted in a conventional floating slab system for thermal insulation or vibration absorption may amplify the vibration of the slab system at specific frequency ranges depending on the material properties of the sheet. The amplified vibration, consequently, results in the heavy weight floor impact noise exceeding the sound level limit for an apartment house, 50dB. In this study, the amplification mechanism is examined through numerical analysis and a new slab system is proposed to reduce the amplification and control the noise. The new slab system consists of studs connecting the base slab and upper concrete finishing yielding the dramatically increased stiffness of the slab. The numerical simulation is performed to investigate the effect of the slab system with studs on the vibration and noise control. The results show that the performance of the slab is sensitive to the number and location of studs, and the heavy weight floor impact noise can be reduced up to 6-7dB compared to the conventional slab system at the optimal stud location.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.89-90
• /
• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.04a
• /
• pp.310-311
• /
• 2014

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.323-324
• /
• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.874-878
• /
• 2003

Acoustic materials are used for the purpose of absorbing noise and reducing transmission of sound into the receiving room. The purpose of this research is to predict the performance of absorbent materials with respect to absorbing behavior and transmission loss as possible as accurately. The performance of the absorbent materials are carried out systematically as follows: The Biot parameter are measured, first. Then using above parameters as input, LMS's SYSNOISE and VIOLINS programs are used to predict absorption coefficient and transmission loss values, which magnitudes are compared with experimental results. As an sample acoustic material, SK SKY VIVA and PET are selected.

• Journal of KSNVE
• /
• v.10 no.6
• /
• pp.963-970
• /
• 2000

The turbo chiller uses centrifugal compressor, which operates at about 14,500 rpm. Due to the high rpm of the impeller, the noise of chiller males one of the serious problems. The possibility of the sound reduction by using absorbing material is studied in this paper. The generated sound propagates through the duct and then radiates to the outer field. So, the use of sound absorption material inside the duct is one of the effective methods. To study the effect of location of the material, we use Boundary Element Method to analyze the sound field inside the duct system. Numerical study shows the highest sound pressure region is near the elbow of curved duct. From the numerical study, it is also shown that appropriate use of sound absorbing material at this region makes 8dB reduction of the highest noise level.

• Journal of KSNVE
• /
• v.6 no.5
• /
• pp.635-644
• /
• 1996

In this paper, Allard's modelling method which employs the method of acoustic transfer matrix(ATM) is applied to yield more precise results in the analysis of porous sound absorbing material. The method of ATM, based on Biot's theory, is known to play an important role in the estimation of the sound absorption when a sound projects onto the material. In the case of a single layered porous sound absorbing material, the surface impedance and the absorption coefficient by using the method of ATM are estimated. With the variation of the material properties, sound absorption characteristics and analyzed. Transmission Loss in a combination of the porous sound absorbing material with a thin plate is predicted.