• International Journal of Internet, Broadcasting and Communication
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• v.4 no.1
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• pp.1-2
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• 2012

A speaker is a system which produces sound through electromechanical operations. It transforms electronic signals into audible sound signals. Almost all speakers are three dimensional. These days, many mobile electronic devices such as mobile electronic devices have become smaller and thinner. A problem with this miniaturization, however, is that the volume of speakers has also decreased. In contrast to conventional three dimensional speakers, we have invented a new type of two dimensional flexible speaker by utilizing the reverse piezoelectric effect.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.83-88
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• 2001

The sound absorption coefficient of glass wool (bulk density of 48 kg/m:1 and 32 kg/m7) was measured by reverberation room method as varying their cross-sectional area. The results show that the absorption is larger for smaller samples because of edge effect. The absorption coefficient with two different kinds of sources. 1/.7-octave band and while noise, gives similar values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.675-680
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• 1997

The object of this study is the numerical analysis about the sound pressure distribution in reverberation rooms. In order to obtain the effect of the boundary conditions of the wall, the sound field was computed for various absorption coefficients and impedances. And the effect of the room shape was investigated by dealing with pentagonal type as well as the rectangular type. In addition an experiment was performed for the sound pressure distribution in a reverberation room and the result was compared with the analysis.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.702-706
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• 2009

Internal running noise of a vehicle running in open field is the summation of air borne noise and structure-borne noise. In this paper vibration damping characteristics of carbody are investigated to see the effect of sound-deadening paint on the internal running noise. By using SEA method, vibration levels of complete train with and without sound-deadening paint are estimated and structure borne noise levels are estimated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.5-10
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• 2004

Apartment Buildings have particularity to cluster together, especially, floor is close to resident, it is subject to dissatisfaction about impact noise between up and down floors. However, we require standard for counterplan to reduce the impact noise of floor. In point of fact, it difficult to objective evaluate for performance sound insulation that not physical sound volume but orignal form, means and effect of sound caused to complex noise in apartment house. Unique type of dwelling and structure pattern cause to noise of floor impact which is established by law for standard regulation. It is object to analysis and compare the result of performance sound insulation of upper floor impact and sample construct the subject resilient material of sound insulator

• Journal of KSNVE
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• v.9 no.4
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• pp.693-702
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• 1999

We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4E
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• pp.3-8
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• 1996

The bubble size distribution is critical information to understand sound propagation and ambient noise in the ocean. To estimate the bubble size distribution in a bubbly water, the sound attenuation has been only in the conventional acoustic bubble sizing method without considering the sound speed variation. However, the effect of the sound speed variation in bubbly water cannot be neglected because of its compressibility variation. The sound attenuation is also affected by the sound speed variation. In this paper, a coherent acoustic bubble sizing inverse technique is introduced as a new bubble sizing technique with considering sound speed variation as well as the sound attenuation. This coherent sizing method is theoretically verified with the bubble distribution functions of single-size, Gaussian, and power-law functions. Its numerical test results with the coherent acoustic bubble sizing method show good agreement with the given bubble distributions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.134-137
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• 2014

The noise reduction performance of a passive facility is dependent on the its length or volume. In other words, this means that the larger the size of passive facility is, the better the noise reduction performance is. The sound directivity control has been proposed as an alternative for the noise reduction without a passive facility. The purpose of this study is to investigate the correlation between the flange attached to inclined exit of the tube and sound directivity when the sound radiates from the tube to the outside. As a result, the sound radiated from flanged tube had weak sound directivity in the wide angle. Also as the flange was bigger, the sound pressure level was lower in the behind the flange.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1194-1197
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• 2006

Recently, international standard for measurement of sound absorption in a reverberation room has been amended. In the revised version, temperature, humidity and air pressure conditions are strictly restricted and also the concrete procedures are presented to reduce the differences in test results by adding inspection of diffusion, measurement uncertainty etc. In this paper, the systematic tests are conducted based on the inspection guide of diffusion defined by ISO 354 and the effects of diffusers on the measurement of sound absorption ratio are considered. As a result, we perceived that the averaged sound absorption ratio in mid and high frequency range is expected to measure around $0.05{\sim}0.1$ higher in high sound absorption material. Therefore, as for the reverberation room for measurement of sound absorption, we need to take into consideration not only the spatial standard deviation of sound pressure mandated by ISO 3741, but also, inspection regulation of diffusion showed by ISO 354.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.03a
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• pp.265-269
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• 1999

This study was carried out to evaluate human subjective sensation for fabric rustling sounds and predict the sensation with quantified sound color measurements and mechanical properties of fabrics. Thirty subjects at Virginia Tech were asked to evaluate seven sound sensation descriptors by semantic differential scale after hearing eight different fabric sounds. Sound measurements were quantified by calculating total sound pressure(LPT), level range(ΔL), and frequency difference (Δf). Mechanical properties of fabrics were measured by KES-FB. Subjective sensation for fabric sound showed significant differences among fabrics except clearness sensation. Subjective sensation predicted by sound measurements showed well fitted regression equation with ΔL and LPT> Sharpness, clearness, and highness were significantly released with mechanical properties of fabrics. All sensation was found to be predicted with sound measurements L:PT and Δf and mechanical properties such as LT, 2HG5, WC, T, and W.