• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1241-1246
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• 2001

In this study, we measured and analyzed the interior noise, the rolling noise and the engine noise at Honam line(Seodaejeon- Jangseong) for passenger and power cars. The noise level is below 69㏈A for Seamaeul PMC(Powered Motor Car) coachs, below 65㏈A for Seamaeul and Mukungwha coachs, over 80㏈A for the driver's room of PMC and DEL (Diesel-Electric Locomotive). We also proposed the criteria of interior noise in free field conditions, below 67㏈A for passenger cars, below 86㏈A for power cars.

• Journal of KSNVE
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• v.9 no.5
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• pp.998-1004
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• 1999

The passenger car manufacturer should meet more and more strict requirements of customers on noise and vibration problems. It is proven that the Taguchi method is a powerful tool for improving the product quality in many areas. This paper employs the Taguchi method to reduce low-frequency booming noise in a passenger car. Selection of object function is very important to minimize interaction effects in the Taguchi method. We select logarithmic-scaled sound pressure level as an object function, which is commonly used to analyze the noise and vibration signals. The optimum noise level predicted with additive-model assumption agrees well with the test results. In addition, the optimum level is lower than the initial one by about 5 dB without any adverse effects. The results show that the Taguchi method can be applied efficiently to solve the noise problem in the passenger cars.

• Journal of KSNVE
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• v.9 no.4
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• pp.785-794
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• 1999

The panel contribution analysis to reduce interior booming noise of a passenger car is carried out using both experimental method and numerical one. The accelerations of panels are measured on the outer surface of car body during operation. The acoustic characteristic of cavity is represented by two different ways. One is the acoustic transfer function obtained by experiment with reciprocal manner. The other is the boundary element model and numerical results of the model are calculated using SYSNOISE. The results from numerical method show more good agreement with measured sound pressure levels than the experimental one. Contributions of panels for interior noise are ranked and structure of the car is reinforced according to the results, which shows that the panel contribution analysis is a powerful tool to lessen structure-borne noise of passenger vehicle.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.67-73
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• 2007

This study analyzes the interior noise that is generated during acceleration of a passenger car in terms of car body structure and panel contribution. According to the transfer method, interior noise is classified into structure-borne noise and air-borne noise. Structure-borne noise is generated when the engine's vibration energy, an excitation source, is transferred to the car body through the engine mount and the driving system and the panel of the car body vibrates. When structure-borne noise resonates in the acoustic cavity of the car interior, acute booming noise is generated. This study describes plans for improving the car body structure and the panel form through a cause analysis of frequency ranges where the sound pressure level of the rear seat relative to the front seat is high. To this end, an analysis of the correlation between body attachment stiffness and acoustic sensitivity as well as a panel sensitive component analysis were conducted through a structural sound field coupled analysis. Through this study, via research on improving the car body structure in terms of reducing rear seat noise, stable performance improvement and light weight design before the proto-car stage can be realized. Reduction of the development period and test car stage is also anticipated.

• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.399-404
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• 2002

Analyzing acoustic-structural systems such as automobiles and aircraft the FRF-based substructuring method is one of the most powerful tools. In this paper, an optimization procedure far the engine mount system of passenger car has been presented using the design sensitivity analysis based on the multi-domain FRF-based substructuring formulation. The proposed method is applied to an optimization problem of the engine mount system, of which objective is to minimize the interior sound over the concerned rpm range. The design variables selected are the stiffnesses of the engine mounts and bushes. Plugging the gradient information calculated by the proposed method into nonlinear optimization software, we can obtain the optimal stiffnesses of the engine mounts and bushings through design iterations. The optimized interior noise in the passenger car shows that the proposed method is very useful in the realistic situation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.445-451
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• 2003

Booming sound is one of the most important interior sound of a passenger car. The conventional booming noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level cannot give the whole story about the booming sound of a passenger car. In this paper, we employed sound metrics, which are the subjective parameters, used in psycoacoustics. According to recent research results. the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network theory has been applied to derivation of sound quality index for booming sound of a passenger car.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.114-119
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• 2003

Passengers are much interested in ineroir noise caused speed-up and mass reduction of railway vehicles. Generally, the major noise source for passenger cars are rolling noise and aerodynamic noise. The purpose of this paper is to evaluate the noise level and to analyze the noise sources for domestic and KTX trains. We also measured the interior noise and the rolling noise for passenger cars. In result, the noise level is below 65dBA for Seamaeul coachs, and below 66dBA for KTX coachs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.332.2-332
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• 2002

Booming sound is one of the most important interior sound of a passenger car. The conventional booming noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level can not give the whole story about the booming sound of a passenger car. In this paper, we employed sound metric which is the subjective parameter used in psychoacoustics. (omitted)

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.178-185
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• 2001

This paper describes the correlation between the interior noise and the trunk wall vibration. Using the vibro-acoustic reciprocity, effect of the trunk wall vibration on the compartment noise is investigated on a medium size car. In the low frequency range, vehicle interior noise is dominated by several acoustic modes of the passenger compartment and the vibration modes of the surrounding shell parts. Especially, vibration of the trunk wall radiates sound and it is transferred through holes on the package tray into the passenger compartment. This paper experimentally reveals that sound can be well produced at some particular vibration modes of the trunk lid and it strongly influences the compartment noise through package tray holes. Contributions of the trunk walls to the interior noise are estimated by measuring the acoustic-structural transfer function, based on the vibro-acoustical reciprocity theorem.