• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.3 s.120
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• pp.201-206
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• 2007

It is important to consider the sound absorption characteristics of building interior decoration materials when we design a building and simulate acoustics in a room. The purpose of this study is to accumulate acoustic data on building interior decoration materials and give a basic data for improving the sound absorption performance by testing the sound absorption coefficients of 9 types of ceiling materials, 14 types of wall papers and 20 types of floor papers.

• Journal of Power System Engineering
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• v.12 no.4
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• pp.46-51
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• 2008

Honeycomb panel has a constructive advantage because it is constructed with a honeycomb core, so it has relatively higher strength ratio to weight. Therefore honeycomb panel has been used as the light weight panels in the high-speed railway technology and high-speed ship like as cruise yachts. Also it has been used in the aircraft and aerospace industry as a structural panel because light weight structure is indispensible in that field of industry. Recently, the honeycomb panel is embossed in the viewpoints of high oil prices as the lightweight panel of the transport machine, however the sound insulation capacity of the honeycomb panel is poorer than those of uniform and another sandwich panels. In this paper a method to improving the sound absorption coefficient of a honeycomb panel Is studied by using the Helmholtz resonator. The sound absorption coefficients for some kinds of honeycomb cores are demonstrated by the normal incident absorption coefficient method.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.2
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• pp.87-96
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• 2004

Acoustic performances of the steel-wire fabrics manufactured from the crushed tires were experimentally investigated for various thicknesses and bulk densities. The well- known two-cavity method was used to measure the characteristic impedances, the propagation constants, and the absorption coefficients. The normal absorption coefficients measured by the two-cavity method agreed well with those measured by the two-microphone impedance tube method. The experimental results showed that the magnitude and frequency range of the absorption coefficient were controllable by changing the thickness and the bulk density of the steel-wire fabrics. Therefore, the steel-wire fabrics from the crushed tires can be successfully used as a good sound absorbing material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.902-907
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• 2002

An equivalent electroacoustic circuit approach of estimating the sound absorption coefficient for parallel perforated plate system is proposed. The proposed approach is validated by comparing the calculated absorption coefficients of a parallel single layer perforated plate system with the values measured by the two-microphone impedance tube method for various porosity and the number of perforated plate. The sound absorbing performances of parallel and series perforated plate systems are compared and discussed from a standpoint of frequency bandwidth with sound absorption. The proposed approach is further extended to the parallel double layer perforated plate system.

• KIEAE Journal
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• v.1 no.2
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• pp.47-54
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• 2001

Single sound absorbers such as porous materials, panels, and Helmholts resonators have limited performance with some extents of frequency region. For example, porous materials do not attenuate low frequency sounds, while panels do not absorb high frequency sounds. Composite absorption structure with coverings, porous materials, and air gaps are an alternative for wide band sound absorption. Slits, panels, perforated panels are those materials for coverings, glass wool, mineral wool, polyester, and polyurethane are frequently used porous materials. Air gap between the porous material and background surface is one of major factors which governs the absorption characteristics of composite absorption structures, especially in the low frequency area. Calculations and measurements show that the absorption coefficients of composite absorption structure, in mid and low frequency bands, are getting higher with increased air gaps. Perforated panels rather than slits and panels are good coverings with higher number as far as absorption coefficient is concerned. Perforated panels with porous materials and 37 cm of air gaps in background have high absorption coefficients for all frequency bands, above 0.7 to 1.0. All measurements are performed in reverberation chamber, Mokpo National University, according to ISO 354 and ISO 3382.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.896-901
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• 2002

The sound absorption coefficients for multiple layer perforated plate systems containing several compartments with airspaces and porous absorbing materials are estimated using the transfer matrix method developed in the previous paper. The absorption coefficients from transfer matrix method agree well with the values measured by the two-microphone impedance tube method for various combinations of perforated plates, airspaces or porous materials. Based on these results, a guidance for the design of multiple layer perforated plate systems combined with airspaces and porous absorbing materials is discussed in detail.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.388.1-388
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• 2002

The sound absorption coefficients for multiple layer perforated plate systems containing several companments with airspaces and porous absorbing materials are estimated using the transfer matrix method developed in the previous paper. The absorption coefficients from transfer matrix method agree well with the values measured by the two-microphone impedance tube method fur various combinations of perforated Plates, airspaces or porous materials. (omitted)

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.3
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• pp.177-186
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• 1998

For the purpose of finding out the sound field characteristics in a cavity of a rectangular enclosure with foamed aluminum lining, analytical and experimental studies are performed with random noise input. Experimental method using two-microphone impedance tube measures the absorption coefficients and the impedances of simple sound absorbing materials. Measured acoustical parameters of the test samples are applied to the theoretical analysis to predict sound pressure field in the cavity. The sound absorp- tion effects from measurements are compared to prediction in both cases with and without foamed aluminum lining in the cavity of the rectangular enclosure.

• Journal of the Korean Wood Science and Technology
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• v.39 no.4
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• pp.326-332
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• 2011

Radial variation of sound absorption capability and air permeability of yellow poplar (Liriodendron tulipifera) wood in cross sectional surface and effect of steam explosion treatment were estimated by the two microphone transfer function method and the capillary flow porometry, respectively. The sound absorption coefficients of steam explosion treated wood was higher than those of control wood and these values increased with frequency. Abundant and big vessel may behave as sound absorbing pore observed on the cross sectional surface of yellow poplar wood. The sound absorption coefficients and air permeability of sapwood were higher than those of heartwood for Liriodendron tulipifera.

• Journal of the Korean Wood Science and Technology
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• v.40 no.1
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• pp.38-43
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• 2012

Sound absorption capability and mechanical properties such as MOE and MOR in bending of miscanthus particle based board were estimated by the two microphone transfer function method and three point bending method, respectively. The results are summarized as follows: The sound absorption coefficients of miscanthus particle based board was higher than those of commercial gypsum board which is well used as sound absorbing barrier. The MOR and MOE of miscanthus particle based board increased with increasing of board density. The sound absorption coefficients of miscanthus particle based board were 50~80% in the frequency range of about 1~2.5 Khz. In entire frequency range, those value increased with target board density decreasing.