• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.149-154
• /
• 2001

Ship owners are demanding quieter vessels since crews have become more sensitive to their acoustic environment. Accordingly, designers of shipyards need to respond intelligently to the challenging requirements of delivering a quiet vessel. In early design stage, to predict shipboard noise the statistical approach is preferred to other methods because of simplicity. However, since the noise characteristics of the ships vary continuously with the environments, it is necessary to update the prediction formula with data base management system. This paper describes the feature of database program with the prediction method. Database management programs with GUI, are applied to Intranet system that is accessible by any users. Statistical approach to the prediction of A-weighted noise level in ship cabins, based on multiple regression analysis, is conducted. The noise levels in ship cabins are mainly affected by the parameters of the deadweight, the type of ship, the relative location of engines and cabins, the type of deckhouse, etc. As a result of verification, the formulas ensure the accuracy of 3 ㏈ in 83 % of cabins.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.333.1-333
• /
• 2002

This paper suggests the noise reduction method of the engine cooling fan. It was estimated the fannoise contribution at the engine room and identified the noise source at the rotating fan by sound intensity method, first. And it has been developed the program for predicting the noise spectrum of axial flow fan. The radiated acoustic pressure is expressed the discrete frequency noise peaks at BPF and its harmonics and the line spectrum at the broad band by the noise generation mechanisms. In this paper it is shown that the comparison of the measuted and calculaed noise spectra of fn for the validation of the noise predictiong program. And this paper presents the characteristics of a fan noise due to modify the design parameters. Accordingly, it was obtained the design parameter values for noise reduction of fan.

• The Journal of the Acoustical Society of Korea
• /
• v.16 no.1E
• /
• pp.49-56
• /
• 1997

Ultrasonic cleaning at high frequency around 1 MHz, called megasonic cleaning, is commonly used to remove particles less than 1 ㎛ by generating high frequency accelerations on the cleaning objects. Cleaning is performed in an ultrasonically-excited liquid contained in a double-structured container. Ultrasonic waves generated by piezoelectric transducers propagate in the outer container and are transmitted through the inner container. The bottom of the inner container is inclined to make oblique incidence of the ultrasonic wave in order to raise the efficiency of the transmission through the bottom plate. This work deals with the efficiency of the transmission, which directly affects the cleaning performance. The transmission characteristics of the ultrasonic wave in the megasonic cleaner have been obtained analytically and numerically for the variations of some parameters, such as the thickness and inclined angle of the bottom plate of the inner container and the chemical ratio and temperature of the cleaning liquid. The calculated results have yielded the optimum cleaning condition in terms of the sound power transmitted into the cleaning liquid.

• International Journal of Internet, Broadcasting and Communication
• /
• v.8 no.4
• /
• pp.48-53
• /
• 2016

Noise and vibration pollution is emerging to people in high speed trains. And it is difficult to realization of eco-friendly railway system at noise problem. The railway internal noise is 73dB on average and over 80dB in the loudest section. In order to reduce noise, there are passive methods that are far from noise sources and theother active noise reducion method. In this paper, we propose a method of reduce noise by measure and estimate the noise condition of train environment using Bone-Conduction device. We use an anti-phase waveform for canceling of noise characteristic. With this new system, the noise from surrounding environments can be reduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.9 s.114
• /
• pp.971-981
• /
• 2006

This paper presents the design and characterization of a novel fiber optical coupler for intensity modulated fiber optical microphone. Theoretical equations for the optical power coupling are presented in detail including optical path analysis and misalignment. Various optical couplers are simulated and manufactured. A multi-mode to multi-mode coupler is characterized by static and dynamic movements of mirror on a well designed experimental stage.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.563-567
• /
• 2004

In this paper, a remote temperature sensor based on surface acoustic wave is introduced and the issues on design, manufacturing, and test of the sensor are addressed. SAW sensors having single and double electrode are prepared on the 128$^{\circ}$ YX-LiNbO$_3$ Substrate. The frequency responses of SAW sensors on the temperature change are compared. To measure the change of center frequency, two center frequencies on the 3dB and 20dB are measured and compared. Since the center frequency on the temperature change from -30$^{\circ}C$ to 80$^{\circ}C$ is linearly changed, the SAW sensor is applicable to the temperature sensor.

• Journal of KSNVE
• /
• v.9 no.3
• /
• pp.466-471
• /
• 1999

The prediction methods of diffraction field in barrier has beenreported much about the infinite length barrier and it is very few work that reasonable sound source was used in experiment. This study, however, has worked about the several model barrier with acoustic scale model experiment. In the case of scale model experiment, it is difficult to use the kind of source with sufficiently characteristics. A spark discharge sound source with the high repeatability, broad band spectra, small size and omnidirectivity has veen used for the prediction of diffraction field. Several model barriers with different length on the ground were considered for the experiment and compared with the the results calculated by the approximation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.724-729
• /
• 2004

An experimental method to investigate the dynamic characteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly compatible with capability of test facilities. It is suggested that the linear wave component that is unable to satisfy similarity is separated with others‥‥‥

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.966-971
• /
• 2000

For the accurate evaluations of influence of construction noise, it is necessary to investigate not only physical characteristics of construction noise but also the subjective psycho-acoustical respects of individual persons. To develope the effective evaluation procedures for construction noise, we investigated Korean vocabularies which can express the feelings for construction noise, and analyzed psychological factors influencing on the subjective feelings of persons, through a series of psycho-acoustical experiments to construction noise. As a result of, it was found that the construction noise sources including the six factors. And this study intends to get the basic data for the evaluations about construction noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.04a
• /
• pp.214-216
• /
• 2012

This paper relates to the automotive silencers reduce noise generated from the actual vehicle for the activity is based on was worth. To do this, the noise from cars to distinguish them by category, characteristics of turbo charger was designed to reduce noise. In order for the design of acoustic modeling using line dynamics, was analyzed using In house & the commercial software programs. Silencers have about several basic elements. Expand, collapse, perforated plate, and the combination are the basic reactive or dissipative elements. Finally, DFSS(design for six sigma) method was designed. and it was verified in vehicle test. The new developed silencers showed good performance vehicle test results. also, the net cost also indicated excellent results compared with other company.