• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1005-1009
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• 2002

The objective of this research is to suggest the noise prediction method of the centrifugal compressor. It is focused on the Blade Passing Frequency (BPF) component which is regarded as the main part of the rotating impeller noise. Euler solver is used to simulate the flow-field of the centrifugal compressor and time-dependent pressure data are calculated to perform the near-field noise prediction by Ffowcs Williams-Hawkings (FW-H) formulation. Indirect Boundary Element Method (IBEM) is applied to consider the noise propagation effect. Pressure fluctuations of the inlet and the outlet in the centrifugal compressor impeller are presented and Sound Pressure Level (SPL) prediction results are compared with the experimental data.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.188-190
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• 2012

Compressed Sensing (CS) has been developed for several years. Among many CS algorithms for image, the Block-based Compressed Sensing with Smoothed Projected Landweber (BCS-SPL) demonstrates its excellent performance in low-complexity and near-optimal reconstruction. Several noise filtering algorithms of image reconstruction have been introduced such as the Wiener or the median filters, etc. In general, each filter has its own advantages and disadvantages depending on specific coding scheme. In this paper, we show that reconstruction performance can be varied according to the choice of filter. When a sub-rate value is changed, different filter causes different effect as well. Concerning the sub-rate, an inner filter can be chosen to improve the reconstructed image quality.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.773-778
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• 2014

Recently both high performance and low noise for a cooling fan used in a server computer have been required. In this study, we measured the noise characteristics for a small cooling fan used in a computer or in a server, and compared the computational data to measured ones. SC/Tetra V10 and FlowNoise V4.3 was used for the unsteady flow field and the aeroacoustic analysis, respectively. The aeroacoustic analysis results have the good agreement with measured data within 3% errors in overall SPL. In the noise spectrum, we could find the peak tonal noise at lower frequency than 1st BPF, and confirm that the reason is caused by the asymmetry of bell mouth shape.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.42-47
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• 2014

In this paper, fatigue life analysis of each structure was performed through theoretical analysis method at design stage in order to verify the success or failure of the store's acoustic noise durability according to the Method 515.5 standard of MIL-STD-810F. In addition, experimental analysis was carried out through the ground and flight test by manufacturing the measuring store, and verification of the sound durability was completed through the flight test after manufacture of the actual store. Furthermore, the commercial FEM code through the PSD calculation method applying measured SPL enables verify the durability of new store components development for the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.156-158
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• 2014

The interior noise of an excavator cabin is important factor related to operation efficiency. For analyzing the cabin air-borne sound, the SEA cabin model was developed using VA One. Analysis result using measured surface SPL of cabin was compared with test data. And the noise reduction guide of cabin was suggested with contribution and sensitivity analysis results of major design variables using developed SEA analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.669-674
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• 1997

A sound field in a reverberation room is analyzed by using numerical methods and the SPL distributions are compared to the measurements. In numerical predictions, the BEM is employed in the low frequency range, while sound ray tracing method is used for the high frequency range. In the BEM analysis, the surfaces of the empty reverberation room are assumed as rigid boundaries and the damping coefficients are estimated from the measured absorption coefficient. The comparisons with measurements for 100Hz shows good agreement. In the sound ray tracing analysis, the predicted energy decay are in excellent agreements with theoretical results. It is shown that the energy absorption by air damping plays an important role as frequency becomes higher.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1459-1464
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• 2006

In the previous studies on railway noise analysis, the main purpose of noise analysis is concerned with the reduction of A-weighted sound pressure level in order to satisfy noise regulations. However, more important facts on noise reduction are the subjective feelings of the human being on noise because people might be annoyed from the noise caused by train. In this paper, railway noise from different type of train are compared using the calculation of sound quality metrics with using strength related method that is calculation of A-weighted sound pressure level.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.950-957
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• 2007

This paper considers acoustic characteristics of silencer within a dry vacuum pump. The main objective is to reduce noise in dry vacuum pump using the new designed silencer. First, SPL and sound intensity are measured for noise source identification and the new model silencer is designed corresponding to noise characteristics. 4-pole parameters are used to predict the transmission loss which is one of the interest characteristics of the new silencer. The calculated transmission loss is then used to change main effective factor and optimal value is selected by using design of experiment. By conducting an experiment, it is proved that the new designed silencer has reduced noise level by 6 dB(A) more than the original one.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2008.10a
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• pp.25-29
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• 2008

본 연구에서는 스포츠웨어 착용 시 운동 속도별로 직물이 스치면서 발생하는 마찰음에 대한 음향특성과 주관적 감각 감성을 고찰하기 위하여, 3종류의 스포츠웨어용 직물 마찰음을 walking(0.63m/s), jogging(1.10m/s), running(0.98m/s)의 3가지 속도로 녹음한 후, 총음압(SPL)과 Loudness(Z), Sharpness(Z), Roughness(Z), Fluctuation Strength(Z)를 계산하였다. 이들 마찰음에 대한 주관적 평가는 9개 쌍의 형용사(시끄러운, 높은, 날카로운, 거친, 딱딱한, 탁한, 변화있는, 거슬리는, 불쾌한)에 대해 의미미분척도로 평가되었다. Jogging시 직물의 마찰음은 가장 시끄럽고 거슬리며 불쾌하게 평가되었고, running시의 직물 마찰음은 walking시나 jogging시의 마찰음보다 덜 시끄럽고 거칠기와 탁한 정도가 적으며 거슬리고 불쾌한 정도가 가장 적게 평가되었다.

• Journal of Biomedical Engineering Research
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• v.10 no.2
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• pp.97-101
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• 1989

N1 and N2 gross neural action potentials were measured from the round window of the guinea pig cochlea at the onset of the acoustic stimuli. N1-N2 audiograms were made by means of regulating stimulant intensities in order to produce constant N1-N2 potentials as criteria for different input tone pip frequencies. The lowest threshold was measured with an input tone pip I5 dB SPL in intensity and 12 KHz in frequency when the animal was in normal physiological condition. The procedure of experimental measurements is explained in detail. This experimental approach is very useful for the investigation of the Cochlear function. Both noN1inear and active functions of the Cochlea can be monitored by N1-N2 audiograms.