• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제23권8호
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• pp.752-758
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• 2013

The effect of external leakage on the acoustic performance of Helmholtz resonators is experimentally and numerically investigated. The transmission loss of the Helmholtz resonator with a circular perforated hole is measured by using an impedance tube setup. The experimental results are then compared with one-dimensional analytical and three-dimensional numerical results. As the size of the hole increases, the peak of the transmission loss shifts to higher frequency, especially for the holes on the cavity. While the transmission loss is almost independent of the location of the hole on the cavity, the impact of the hole location on the neck on the transmission loss is not negligible. The results show that one-dimensional analytical method can predict the overall trends, whereas three-dimensional numerical method is necessary for more accurate predictions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.242-242
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• 2013

Recently, importance of working environment is increased in commercial vessel and offshore structure. Marine facility design and ambient environment condition are influenced to enhancing human performance and reducing human errors. Consequently, the quality of accommodation where offshore facility crews sleep, eat and relax will influence their job performance and overall sense of comport and well-being. Therefore, adequate acoustic isolation between adjacent spaces is normally required to achieve satisfactory internal noise levels, acoustic privacy and speech intelligibility. In this study, the reverberation time is investigated in the public areas where there are not provided the information of material's noise reduction coefficient (NRC). The experiment of reverberation time is rarely performed for the various type public areas in a marine structure. Therefore, the reverberation time in a vessel is investigate in order to evaluate the room's noise reduction coefficient (NRC) in a public area.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.338-344
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• 2003

The seismic analysis method of spent fuel storage structures for PHWR plant is introduced in comparison with the method for PWR plant. Investigating the structural characteristics of the storage structures, the former is vertically stacked fuel storage trays, while the latter is welded honeycomb type structure. However, as both structures are submerged and free standing, the analysis methods to anticipate the seismic response of both structures are complicated. For the better estimation of actual seismic response, how to model the dynamic properties and the structural behaviour is the key issue. In this paper, the overall procedures of the seismic modelling and stability check for seismic sliding and overturning of the two different storage structures are discussed in the viewpoint of analysis reliability

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.109-115
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• 2003

This study intends to provide an optimum design of flexible matrix composite driveshafts using a genetic algorithm. An objective function is defined as a combination of shaft flexibility, whirling stability and torsional buckling and the design variables are selected as ply angles and the shaft thickness. Results show that the genetic algorithm can successfully find an optimum solution at which the overall performance of the FMC shafts is significantly enhanced

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제14권10호
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• pp.968-974
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• 2004

Automakers have been forcing their suppliers to guarantee qualities of parts. Then, the suppliers have met the fundamental quality requirements such as dimensions and functions, but they could not sufficiently satisfy the automakers' noise requirements yet because automatic noise inspection systems were little successfully adopted In mass-production lines. This study tried to develop a system for automatically checking noise radiated from a rotating engine part and filtering parts emitting noise higher than criteria: the upper limits of a overall noise level or a noise spectrum. A commercial noise measurement system was used for measuring noise, and then the noise data was transmitted to a governing program through OLE(object, linking and embedding) functions. The governing program, belonging to a total noise inspection system managed the noise measurement and analysis. This system was successfully adapted for distinguishing bad parts according to the noise criteria.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.880-884
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• 2014

RT (reverberation time) of outdoor spaces surrounded by multi-storey buildings depends on many designable factors such as the openness, volume and building layouts, etc. This study therefore aims to clarify the influential factors for RT in outdoor spaces surrounded by buildings with complicated topographical conditions. A series of measurements were carried out for 15 outdoor spaces in 6 apartment complexes with different building layouts. An Empirical method considering the openness, averaged ray length and building high is also suggested, to predict RT approximately in the outdoor spaces. The overall results suggest that RT in outdoor spaces of apartment complexes is significantly influenced by source-receiver distance and building layouts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제12권3호
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• pp.187-194
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• 2002

A seven-port impedance and admittance matrices of multilayered piezoelectric beam are derived for the analysis of piezoelectric AFM ( atomic force microscope) cantilever that is partially covered by the piezoelectric layer. The variational principle is used for deriving the extensional and flexural motional equations and the conjugate parameters. Overall impedance matrix of AFM cantilever can be obtained by combining two impedance matrices of the covered and the non-covered. she resonance and antiresonance frequencies and the effective electromechanical coupling factors are calculated using the derived matrices. The results and the three dimensional finite element solutions are compared with the experimental results in other publication.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.364-369
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• 2012

The vehicle sound classified into driving sound due to power-train, operating sound due to electric motor like sunroof, door lock and electronic sound. These vehicle sound has various features depend on the characteristic of sound that user required. And it based on cultural and regional difference of user. In this study, the user required vehicle sound characteristics for luxury sedan was investigated in overall viewpoint. And virtual target sound was developed through the result of user preference investigation. Next, Jury test was carried out in Germany, USA and Korea for evaluating the target sound. And the regional and individual difference of preference was analyzed through the result of jury test. This result of research will be contributed to design of vehicle sound quality and target sound setting.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.617-621
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• 2003

Existing loudness models are specified only to diotic sounds in spite of the fact that normal human beings hear dichotic sounds. Approximately, the arithmetic mean of loudness values of both ear signals has been suggested for the resultant perceived loudness. In this study, the dependence of overall loudness perception on the interaural level differences was investigated by the subjective tests. It was found that the larger the interaural level difference, the louder the perception than the mean of calculated loudness values at both ears and the lower the critical band rate or the reference level, the louder the perception than the mean value. A modified loudness model was proposed to he applicable to dichotic sounds by using the equivalent diotic levels.