• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1157-1160
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• 2002

This paper describes an investigative study for Wind Noise of Passenger Cars. Using statistical method of analyzing jury preference data, we extract important sound quality metrics for subjective feeling and also md important frequency band. It will be helpful for development of wind Noise improvement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.353-356
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• 2003

Acoustic holography is adopted in identifying the noise sources of a vehicle's underbody. Wind noise from a vehicle's underbody accounts for a large portion of the overall noise level due to the complex flow structure. Current study presents the development process of acoustic holography in the vehicle underbody, and discusses the results obtained using the method. Difficulties associated with using acoustic holography as well as the implication of the results regarding future noise reduction possibilities are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.34-40
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• 2001

Aeroacoustic technology to improve the acoustic comfort in high-speed became a major topic in vehicle development process. Although most of wind noise reduction and sound quality improvements are possible with full vehicle, the countermeasures should be applied at the early design stage. Acoustic holography technology was used to identify the external wind noise sources of a vehicle in Hyundai Aeroacoustic Wind Tunnel. Microphone self-noise reduction techniques and several reference microphone positions are investigated in order to obtain proper results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.1073-1075
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• 2003

본 글은 가전제품의 안전성, 고급화 및 기능의 차별화를 목적으로 Auto Louver를 설치하는 경우에 있어서 부수적으로 발생하는 2차적 소음에 대해 음질개선 및 소음저감 방법을 소개한다. 실험은 제품의 토출구에 안전망이 설치되고 그 뒤에 Auto Louver를 부착한 자사의 Air Cleaner를 대상으로 실시하였으며, 임의의 공기가 토출되는 조건에서 Auto Louver의 Blade 길이를 줄여 안전망과 Blade 끝단까지의 거리를 이격시킴으로서 1.2KHz-2.5KHz 주파수 대역의 SPL의 저감을 통해 음질을 개선하였고, 이로 인해 토출구로부터 1m 떨어진 위치에서의 소음 측정값을 1.1㏈A의 저감하는 효과를 얻을 수 있었다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2546-2551
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• 2007

Weather Strip(W/S) is a rubber part to proof water, sound and dust for opening and shutting devices including vehicle doors. And it requires high dimension precision and durability to proof water, noise, vibration and etc. But ironically it itself makes some wind noise because of some protuberance with glasses. The air flow analysis of door part of vehicle makes it possible to calculate and find out the cause of wind noise. In previous analysis, we focus on the numerical air flow analysis of the automobile side part. We do 2D-C.F.D first and 3D second. Through simulations, we can calculate the amount of sound pressure level at the glass run and find out the effects of glass run to make wind noise. Finally we can improve shape of glass run to reduce wind noise although it is small amounts of sound pressure reduction compared with total vehicle noise level.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.292-299
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• 2018

The vehicle exterior design is the main parameter of aerodynamic wind noise, but the modification of it is nearly impossible at a proto-type stage. Therefore, it is very important to verify exterior design and estimate the correct wind noise level at the early vehicle design stages. The numerical simulations of aerodynamic wind noises around A-pillar and wiper were developed for specific vehicle exterior designs, but could not be directly used for the discussions with designers because these need complex modeling and simulation process. This study proposes new approach to A-pillar and wiper wind noise estimation at design stage using response surface methodology of modeFRONTIER, of which database is composed of PowerFLOW simulation, PowerCLAY modeling, SEA-Baced (Statistical Energy Analysis-Based) interior noise simulation, and turbulent acoustic power simulation. New design parameters are defined and their contributions are analyzed. A state-of-the-art, easy and reliable CAT (Computer Aided Test) tool for A-pillar and wiper wind noise are acquired from this study, which shows high usefulness in car development.

• Composites Research
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• v.34 no.3
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• pp.192-198
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• 2021

Due to enormous market growing of electric vehicles without combustion engine, reducing unwanted BSR (buzz, squeak, and rattle) noise is highly demanded for vehicle quality and performance. Particularly, innerbelt weatherstrips which not only block wind noise, rain, and dust from outside, but also reduce noise and vibration of door glass and vehicle are required to exhibit high damping properties for improved BSR performance of the vehicle. Thermoplastic elastomers (TPEs), which can be recycled and have lighter weight than thermoset elastomers, are receiving much attention for weatherstrip material, but TPEs exhibit low material damping and compression set causing frictional noise and vibration between the door glass and the weatherstrip. In this study, high damping EPDM (ethylene-propylene-diene monomer)/PP (polypropylene) thermoplastic vulcanizates (TPV) were investigated by varying EPDM/PP ratio and ENB (ethylidene norbornene) fraction in EPDM. Viscoelastic properties of TPV materials were characterized by assuming that the material damping is directly related to the viscoelasticity. The optimum material damping factor (tanδ peak 0.611) was achieved with low PP ratio (14 wt%) and high ENB fraction (8.9 wt%), which was increased by 140% compared to the reference (tanδ 0.254). The improved damping is believed due to high fraction of flexible EPDM chains and higher interfacial slippage area of EPDM particles generated by increasing ENB fraction in EPDM. The stick-slip test was conducted to characterize frictional noise and vibration of the TPV weatherstrip. With improved TPV material damping, the acceleration peak of frictional vibration decreased by about 57.9%. This finding can not only improve BSR performance of electric vehicles by designing material damping of weatherstrips but also contribute to various structural applications such as urban air mobility or aircrafts, which require lightweight and high damping properties.