• Proceedings of the KSR Conference
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• 2003.10c
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• pp.132-137
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• 2003

This paper concerns the prediction of railway noise propagation using scale model experiment in acoustics. In order to make acoustical experiment the digital signal processing technique are applied and spark discharge sound sources have been developed in which impulse response measured in 1/20 scale model railway. In the case of scale model experiment, it is difficult to realize sufficiently small size and directivity and to get sufficient sound energy and to get repeatability. Several type of Spark discharge sound source is made in laboratory. Experiment results are compared with the calculated results by the prediction model. As the results, it was found that railway noise could be predicted in acoustical scale model experiment using spark discharge sound source.

• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.42-48
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• 2011

This preliminary study is about the application of the compound source to the active noise barrier system as control sources. A compound source is composed of two monopole sources but having opposite phase. However, both monopole sources in one compound source are not independently controlled. The source strength of monopole source close to the noise source is proportional to the other one. Therefore, the cost for the hardware system is cheaper than usual system but known to possibly having a similar performance in generating anti-noise acoustic field. In this study, using a simple active noise barrier system model having a non-reflective floor, the effectiveness of the system with compound sources is investigated through computer simulations and shows 30~40 % performance improvement of noise reduction.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.228-236
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• 2021

In order to understand the underwater noise source factor of the linear pump type forced ejection system, a reduced-model compressed water experiment device was developed. The reduced-model compressed water experiment device consists of a reverberation tank, a linear pump type forced ejection device, and an underwater vehicle. The underwater noise source was selected from the hydraulic ram moving speed, the hydraulic ram/piston pipe spacing, the ejection pipe inlet/water ram area ratio, and the number of water ram inlets. The underwater vehicle was ejected into the reverberation tank by the device. The source level was derived from the measured sound pressure. The source level tends to increase as the hydraulic ram/piston tube spacing and the hydraulic ram moving speed increase. The source level tended to increase as the area ratio was increased, but the level was weak. The number of water ram inlet did not affect the source level.

• International Journal of Railway
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• v.4 no.2
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• pp.42-49
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• 2011

Today, rolling stock has become a fast and convenient mode of transportation and has witnessed increased demand. But the speed improvement has resulted in increased aerodynamic noise and therefore residential districts near the railroad tracks are exposed to ever increasing noise level. A study on methodologies for measuring and appraising rolling stock's environmental noise has therefore become an important area of endeavor. In the case of the environmental noise, there are no changes in tone so prediction can be made by reducing areas around the railway. The present study explores estimation of the noise around the railway using scale model, and the source of the noise has been investigated as well. The scale model of rolling stock will have to be able to measure high frequency noise and it is required to be generated in a short amount of time. Since popping a balloon or firing a gun fits this requirement the present study analyzed the characteristics of these two different noise sources. Measurement was made in a large vacant lot and the reflection due to the ground was also examined. The method proposed here can be used in the future for predicting the environmental noise of railway vehicles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.661-667
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• 2004

The characteristics of noise and vibration by a heavy impact source was studied. The triggering method was used for increasing the reliability and stability to measure the level of sound pressure. sound intensity and vibration acceleration. A simple finite element model and a rigid body analysis method were suggested to calculate the natural frequencies of the multi-layer floor system. The results show that the resilient materials decrease the natural frequency of the reinforced concrete slab, make a resonance with dominant driving frequency in the low frequency region, and increase the vibration and noise level. A simple finite element model and rigid body models was suggested to calculate the natural frequencies of the floor systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1579-1587
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• 1999

Bias-dependent noise models of $0.2\mu\textrm{m}$ gate length P-HEMT's which are scalable with gate width are proposed. To predict S-parameters of the P-HEMT's the intrinsic parameters except for $\tau$ subtracted the offsets introduced in this paper are normalized to the gate width and then scaled. The small-signal model parameters are expressed as fitting functions of the drain current to $\textrm{I}_{dss}$ ratio and gate width. In addition, to estimate accurately noise parameters the noise temperature $\textrm{T}_{g}$ of the intrinsic resistance, the equivalent noise conductance $\textrm{G}_{ni}$ of the gate current noise source, and the equivalent noise conductance $\textrm{G}_{no}$ of the drain current noise source are adopted as the noise model parameters. The extracted values of $\textrm{T}_{g}$ are nearly independent of drain current and gate width and their average is around the ambient temperature. The extracted values of $\textrm{G}_{ni}$ are small enough to be neglected to the circuit characteristics. From the comparison of the noise model with only $\textrm{G}_{no}$ and that having $\textrm{T}_{g}$, $\textrm{G}_{ni}$ and $\textrm{G}_{no}$ to the measured data it is fund that even the former model is in good agreement with the measured noise parameters. Thus, from a practical point of view the noise model having only the drain current noise source is confirmed as a scalable bias-dependent model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.172-176
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• 2000

A series of preliminary experiments were carried out to quantify the annoyance are noisiness caused by floor impact noise. From the results of the experiments. the heavy impact source was found to be felt louder and noisier than the light impact source. Measurements of noise were also conducted by a diagnostic system based on the model(the model consists of the autocorrelators and the cross-correlation for signals arriving at two ear entrants) of the human auditory-brain system. Physical factors in the model were calculated by use of the ACF(autocorrelation function) and IACF(interaural cross correlation function) of binaural signals. From the ACF/IACF analysis, it was found that perceived loudness of floor impact noise could be represented by the factors of the ACF/IACF model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.42-49
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• 2009

In this paper, an alternative method was introduced to conduct a transfer path analysis for airborne noise. The method used the transfer function matrix composed of acoustic transfer functions that are referenced by the input voltage of a calibration source. A calibration factor which is converting a virtual voltage to source strength was deduced by vibro-acoustical reciprocity theorem. The calibration factor is then multiplied to the virtual input voltage to estimate the operational source strength. Three loudspeakers were used to noise sources of acrylic half car model. The method was applied to airborne noise transfer path analysis of the half car. The estimated source strength by transfer path analysis was compared the deduced source strength by vibro-acoustical reciprocity to verify the method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.836-842
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• 2001

The more sophisticated patterns of propagation model is presented in this paper, which includes three different source characteristics. The spherical, cosine and dipole radiation characteristics compared and sound event level and the maximum sound level are calculated by experiment and calculation. It is shown that patterns of propagation has dipole characteristics for low speed range(below about 150km/h) at electric multiple system. We know that push-pull high speed system(maximum speed: 300km/h) has cosine characteristics of noise propagation. For this purpose, We conduct the experiment of noise and know the empirical formula of noise level and radiation coefficient K. This model of simulation is conducted through point source array model at wheel/rail contact point by using program and experimental formula. We can guess prediction of profile, flat and wear of wheel by above modeling in near field.

• Journal of the Semiconductor & Display Technology
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• v.19 no.3
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• pp.73-76
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• 2020

The physics-based compact gate leakage current noise models in nanoscale MOSFETs are developed in such a way that the models incorporate important physical effects and are suitable for circuit simulators, including QM (quantum-mechanical) effects. An emphasis on the trap-related parameters of noise models is laid to make the models adaptable to the variations in different process technologies and to make its parameters easily extractable from measured data. With the help of an accurate and generally applicable compact noise models, the compact noise models are successfully implemented into BSIM (Berkeley Short-channel IGFET Model) format. It is shown that the noise models have good agreement with measurements over the frequency, gate-source and drain-source bias ranges.