• Journal of KSNVE
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• v.9 no.1
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• pp.33-41
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• 1999

This paper presents a method of actively controlling the interior noise by a trim panel with hybrid feedforward-feedback control loop. The control technique is designed to minimize the vibration of panel whose motion is limited to that of a piston (out-of-plane motion). The hybrid controller consists of an adaptive feedforward controller in conjunction with a linear quadratic Gaussian (LQG) feedback controller. In order to maintain control performance of both persistent and transient disturbances, the feedback loop speeds up the adaptation rate of feedforward controller by improving damping capacity of secondary plant related with the adaptation rule. Numerical simulation and experimental result indicate that the hybrid controller is a more effective method for reducing the vibration of the panel (and therefore the interior noise) compared to using feedforward controller.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1473-1478
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• 2000

Severe fork-lift truck noise is annoying to an operator as well as one of the noise pollution elements. This paper presents the noise contribution analysis of a cabin type fork-lift truck to identify the major sources and its usage to reduce the interior noise level. The methodologies for this work are sound field analysis, sound intensity test, insertion loss test of duct system and etc. An effective method to suppress interior noise level of fork-lift truck and design guides are suggested.

• Journal of KSNVE
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• v.10 no.5
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• pp.806-810
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• 2000

This paper presents a practical method for reduction of interior noise and improvement of sound quality in compartment of passenger car. The tested vehicle has a booming noise problem at rear passenger seats. In order to identify the transfer path of interior noise, the running modal analysis, the vibro-acoustic frequency transfer response and the noise path analysis are systematically employed. Using these various methods, it has been founded that the rear part of the roof of the test car was a noise source for the booming noise. Through the modification of the roof, the booming noise has been reduced and sound quality inside car also has been improved.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.196-202
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• 2003

The object of this article is to study the plausibility of applying human voice warning system to automobiles. Human voice is considered the best tool for warning system in automobiles. For the purpose of comprehending the specific characteristics of relation between noises and properties of the automobiles indoors and voice warning system researcher performed FRF test in order to examine the characteristics of voice output, and FEM simulation to learn the specific properties of the car indoors. And furthermore, surveyed the quality of voice output, using the written inquiry to examine members. The result of the study shows that it is much possible to apply voice warning system to automobiles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.786-790
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• 2003

The purpose of this research is to observe that the acoustic characters of classroom have some difference by several conditions. TSP has used to measure impulse response and such physical indexes as RT(Reverberation Time), D$\sub$50/, and STI(Speech-Transmission-Index) are computed by it. we investigate difference under some conditions such as when students were present at each classroom and when was not so, and when professor used a microphone and unused it. In this study, we found that reverberation time when people take a seat is lower than was not so. we wish to help one who work for construction industry, as they build a kind of classroom

• KIEAE Journal
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• v.2 no.1
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• pp.41-48
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• 2002

This study aims to investigate and evaluate the room acoustic designs of a multi purpose gymnasiums which do not use adjustable treatments in order to change the acoustical characteristics. Considering the main uses of gymnasium and auditorium, experiments were carried out using both nondirectional speakers on the stage and loudspeaker installed on the ceiling. The result from the study are as follows; Measured RT under unoccupied condition was a little longer than the expected value, therefore, in the case of occupied condition RT would be close to the optimum value. However, parameters that evaluate intelligibility and speech transmission property appeared to be low and have large differences depending on the measuring points, therefore, more effective sound reflecting surfaces and sound reinforcement systems should be considered.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.363-365
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• 2014

기존의 알람 어플리케이션은 음향 효과를 통한 자극이라는 단순한 방식으로 과거와 같거나 알람 해제 방식이 유사한 알람 어플리케이션들이다. 이러한 기존의 방식을 벗어나, 알람을 해제하려는 사용자에게 질문을 하고 그에 대한 답변을 Google TTS로 입력받아 알람을 끌 수 있도록 하였다. 또한 알람 종료 시 블루투스 통신을 이용하여 사용자가 입력한 값에 따라 아두이노를 통하여 실내의 조명과 커튼을 제어하여 더 효과적인 알람 효과를 낼 수 있도록 구현하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.462-467
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• 2000

The aim of this study is to provide fundamental data for acoustic design by analyzing the room acoustic characteristics according to the PA system used in the school gymnasium. The measurements were carried out accordance with the ISO 3382. The sources used in this study were four types; omni-directional, centralized, distribution, the combination of centralized and distribution sound source system. Omni-directional system is recommended by ISO for the acoustic test and the others are installed on the wall, column and ceiling in the school gymnasium for sound reinforcement.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1656-1660
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• 2008

Internal noise level of a train running in tunnel is influenced by sound transmission coefficients of floor, side door, window and gangway as well as by the sound power levels of major noise sources. The structure of a gangway should be strong enough for the safety of passengers while it should be flexible enough for the movement of a train in curves. Due to this the sound transmission coefficients of gangways are relatively low compared to those of carbody structure. The effect of the sound transmission coefficient of the gangway is studied in this paper in regards to the existence of end doors.

• Journal of Korean Association for Spatial Structures
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• v.7 no.5
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• pp.75-82
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• 2007

The present work measured and analyzed changes in the acoustics of a sound field which has a retractable ceiling. An 1/20 scale model of an openable space was built and measurement was carried out by varying the opened area of a ceiling. The most widely used room acoustic and design parameters, RT, EDT, and D50 were investigated. The results suggest that the use of RT as an acoustic design parameter may not be proper in an openable space and further it is likely to mislead the initial acoustic design of such spaces. It is mainly due to the characteristics of RT in which non-exponential decay processes are linearly fitted. Early decay times were found to be decreased in proportion to increaing the ratio of opened area. D50, an index of speech intelligibility, was effectively shows the influence of openings on the acoustics. It is also found that EDT and D50 at the seats, not directly exposed to the opened part of a ceiling, were almost linearly decreased in proportion to the ratio of opened area, while little influence was found for the opening ratio larger than 40% at the directly exposed seats to the opened part of a ceiling.