• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.412-420
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• 2005

This article proposes analytical solutions for sound radiation from radial vibration modes of a thick annular disk. Structural eigensolutions are calculated using the transfer matrix method. The far-field sound pressure distribution is obtained using two alternate methods. In the first method, pressure is calculated using the Rayleigh integral technique. The second method treats sound radiating radial surfaces as cylindrical radiators of finite length. The Sinc function approach is employed for calculations. Acoustic powers and radiation efficiencies of radial modes are also determined from the far-field sound pressure calculations. Analytical predictions match well with measured data as well as computational results from a finite element code in terms of structural eigensolutions and from a boundary element code in terms of sound pressure, directivity etc.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.778-781
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• 1995

In this paper, sound radiation of a rotary compressor used in room air-conditioner is investigated. structural eigenmodes are identified through modal test. Since accumulator is found important factor of sound radiation, damping material was added around accumulator to reduce sound radiation level of rotary compressor. As result, sound radiation was reduced to 3 dB.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.282-282
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• 2000

The analysis of the radiation effect on matter has been performed using stochastic methods. Recently, It was discovered that the detector pulses of radiation can be analysed using deterministic method that utilizes the chaotic behaviour with an attractor found in a noise region. We acquired a time series for pulse tram of Am-241 using scintillation detector and reconstructed a phase space, then performed new analysis for the radiation detection signal by applying embedding theory, Lyapunov exponent, correlation dimension, autocorrelation dimension, and power spectrum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.667-671
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• 2012

Low frequency noises (up to about 200 Hz) mainly occur due to particular modes, resulting in booming noises, and in general the solutions may be found based on mode controls where conventional methods such as FEM can be used. However, at higher frequencies between 0.3~ 1 kHz, as the number of modes rapidly increase, radiation characteristics from structures, performances of damping sheets and sound packages may be more crucial rather than particular modes, and consequently the conventional FEM may be less practical in dealing with this kinds of structure-borne problems. In this context, so-called 'mid-frequency simulation model' based on FE-SEA hybrid method is studied and validated. Energy Transmission loss (i.e. air borne noise) is also studied. A dash panel component is chosen for this study, which is an important path that transfers both structure-borne and air borne energies into the cavity. Design modifications including structural modifications, attachment of damping sheets and application of different sound packages are taken into account and the corresponding noise characteristics are experimentally identified. It is found that the dash member behaves as a noise path. The damping sheet or sound packages have similar influences on both sound radiation and transmission loss. The comparison between experiments and simulations shows that this model could be used to predict the tendency of noise improvement.

• Journal of KSNVE
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• v.9 no.1
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• pp.189-195
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• 1999

The noise radiated by the rotary compressor for a room air-conditioner was investigated experimentally. Noise characteristics and structural eigen modes of the compressor were identified through sound tests and modal tests each other. From these tests. we found that the accumulator has a big contribution to the noise radiation. So, various structural modifications for the accumulator were performed and these modification methods were found efficient to the noise reduction from verification tests.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.78-83
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• 2000

Exterior noise generated by the aircraft induces a serious noise pollution near the airport. For the prediction of an exterior noise radiation of aircraft an empirical formula is employed to model the acoustic sources. It is shown that the fan/compressor noise is the most dominant part of the acoustic sources in all cases.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.569-574
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• 2011

In research vessels or naval ships, airborne noise from machineries such as diesel engine is the major source of underwater noise at low speed. In this paper, effect of engine noise on underwater noise is studied by considering two paths; sound radiation from hull plate and direct airborne noise transmission through hull plate. SEA (Statistical energy analysis) is used to predict hull plate vibration induced by engine noise, where SEA model consists of only two subsystems; engine room air space and hull plate. The pressure level in water is calculated from sound radiation by plate. Engine noise transmission through hull plate is obtained by assuming plane wave propagation in air-limp plate-water system. Two effects are combined and compared to the measurement, where speaker is used as a source in engine room and sound pressure levels in engine room and water are measured. The hydrophone is located 1 m away from the hull plate. It is found below 1000 Hz, prediction overestimates underwater sound pressure level by 5 to 12 dB.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.527-532
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• 2008

In this study, numerical analysis is performed to investigate the sound radiation characteristics of an apartment house according to the type of the slab system. In order to satisfy the boundary condition of the apartment house, the whole floor is modelled with FEM model for three different structural system: wall, RC, flat slab system. From the analytical results, it Is shown that heavy weight floor impact noise of wail type slab is larger than that of the other slab systems and the noise radiated from the wall have great effect on the sound pressure level. The results also show that the vibration energy of RC or flat slab system is widely distributed over the whole slab, which is main reason that the noise induced by the slab systems is reduced in comparison with wail slab system.

• The Journal of the Acoustical Society of Korea
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• v.6 no.1
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• pp.48-57
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• 1987

It is well known that the major noise source of Refrigerator is compressor, and due to the tendency of higher quality and more lighting of manufactured goods, the importance of prevention and reduction of a noise is increasing. In this paper, in order to prevent and reduce such a noise, sound pressure level and acoustic intensity are measured for compressor, and the result of these measurements, the noise radiation characteristics of compressor are reconized. And the experimental modal analysis is applied to the compressor to identify the noise sourcce. As the results of this study, we come to know that the spring, which is used to reduce vibration, does not reduce vibration efficiently, and compressor shell and its mounting system effect the noise radiation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.162-168
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• 2009

In this study, numerical analysis is performed to investigate the sound radiation characteristics of an apartment house according to the type of the slab system. In order to satisfy the boundary condition of the apartment house, the whole floor is modelled with FEM model for three different structural system: wall, RC, flat slab system. From the analytical results, it is shown that heavy weight floor impact noise of wall type slab is larger than that of the other slab systems and the noise radiated from the wall have great effect on the sound pressure level. The results also show that the vibration energy of RC or flat slab system is widely distributed over the whole slab, which is main reason that the noise induced by the slab systems is reduced in comparison with wall slab system.