• Journal of the Korean Society of Safety
• /
• v.12 no.3
• /
• pp.10-16
• /
• 1997

The problem of sound radiation from curved beam under the action of harmonic line forces is studied. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0. The curved beam material and the elastic foundation are assumed to be lossless including a tension force(T), damping coefficient(C) and stiffness of foundation($k_s$) will be employed. The non-dimensional sound power is derived through integration of the surface intensity distribution over the entire curved beam. The expression for sound power is integrated numerically and the results are examined as a function of wavenumber ratio($\gamma$) and stiffness factor($\psi$).

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1026-1032
• /
• 2010

In this paper, To estimate the train exterior noise and environment noise which are occur when High-Speed EMU is driving with the speed of 370km/h, Estimated sound source about noise that is appeared during operation based upon noise SPL values. Based on aero-dynamic noise source and wheel-rail noise source, these were already used to the existed research, we have estimated each sound power about measured noise, and computed the sound source to apply on the High-Speed EMU, and also calculated the sound power in case of the maximum operation speed of 370km/h.

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

• Journal of the Society of Naval Architects of Korea
• /
• v.56 no.5
• /
• pp.464-471
• /
• 2019

The acoustic power is a major acoustical characteristic of an underwater vehicle and could be measured in a reverberant water tank. In order to obtain accurate measurement results, the acoustic field formed by the sound source should be investigated quantitatively in the reverberant water tank. In this research, the acoustic field of a reverberant water tank containing an underwater sound source has been analyzed by using an acoustic radiosity method one of the numerical analysis methods suitable for the acoustic analysis of the highly diffused space. The source level of the underwater sound source and acoustical properties of the water tank input to the numerical analysis have been estimated by applying the reverberant tank plot method through a preliminary experiment result. The comparison of the numerical analysis result with that of the experiment has verified the accuracy of the acoustic radiosity method.

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

• Journal of KSNVE
• /
• v.9 no.4
• /
• pp.761-768
• /
• 1999

This paper presents an NVH test of Automotive power steering system performed at a half-car Test-rig. The test was done for neutral and full turn(or relief) conditions in steering wheel at a fixed rpm first, then followed by the same conditions for the rpm run-up. The sound intensity measurement verified the results from the frequency and order analysis, especially about the identification of major noise sources and their dominant frequencies. The results from thie study can be utilized in the system noise tuning when a new steering component is installed. In particular, the noise and vibration reduction at the relief condition will be accomplished through the knowledge obtained from this study and from the on-going research on the hose tuning techniques usign silencers and tuning cable inserted in the pressure hose.

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.433-438
• /
• 2001

Noise is one of the major environmental problems in human life. To reduce the noise emitted from the control valve it is necessary to develop the measurement method, measurement system, analysis method applicable to the field. In this study IEC and ISO standards were investigated and measurement method for the valve noise was proposed. Noise from the valve was measured in the reverberation room and sound power level was calculated. The sound power level increased as the flow rate and pressure difference increased. The noise characteristics are useful to predict valve noise for given conditions, to compare the performance of different valves and to develope low-noise valves.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.527-534
• /
• 2004

This study is a paper relating to between road traffic noise(RTN) and sound power level(PWL). At present to prediction of RTN is used to many experimental models and prediction methods. RTN is computed PWL using existing experimental models and prediction methods. Then, computed PWL is compared with it of measurement value, in them, it is selected model most similar to measurement value. And then, this results will watch for make Noise Map, as application field applied to computed results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.333-337
• /
• 2003

The use of reactive shearing structural intensity to place small patches of constrained layer damping material in order to achieve the largest reduction in the radiated sound power of Air-conditioner outdoor unit is described. The normal surface velocity of each panel was measured using a laser doppler vibrometer. Experimental results indicated that patches of constrained layer damping material placed over areas of high reactive structural intensity reduced the radiated sound power significantly more than patches of the same area placed over areas of low reactive structural intensity

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1376-1378
• /
• 1997

Mechanical and electrical properties of mica/epoxy composite materials were investigated by dynamic mechanical analyzer(DMA) and dielectric analysis (DMA). Both modulus and permittivity of sound specimens were higher than those of aged specimens. Two results show that $tan{\delta}$ of sound specimens is lower than that of aged specimens. DMA results showed that glass transition temperatures of sound and aged specimens are observed to be $87.16^{\circ}C$ and $88.38^{\circ}C$, which increases with the increase of aging time.