• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.447-453
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• 2009

The interior noise of the High Speed Train(HST) is analyzed by applying the statistical energy analysis (SEA) method. The interior of each vehicle is divided lengthwise into nine cavities. Since the rolling noise and aerodynamics noise are expected to be dominant noise sources, they are treated as the noise sources in the model. To further simplify the model, curtains and seats are excluded. The simulation runs involving one-car, three-car and five-car trains are conducted. The maximum predicted noise level is 98.4dB. The results also show that the predicted noise levels are within 0.23% of each other. The results imply that it is not necessary to estimate the interior noise of the train by constructing multiple-car train models. The noise estimate based on just one-car train can be optimal with respect to the computational effort and modeling time.

• International Journal of Automotive Technology
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• 제8권1호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.591-592
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• 2007

• 산업경영시스템학회지
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• 제24권65호
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• pp.65-73
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• 2001

In this study, psychophysiological stress was quantitatively evaluated at various car interior noise levels by using Electroencephalogram(EEG). An experiment was performed to investigate the most comfortable range of noise level during simulated driving condition. Twelve healthy volunteers participated in the experiment. They were asked to operate the driving simulator while six levels of interior noise were given, such as 45dB(A), 50dB(A), 55dB(A), 60dB(A), 70dB(A), 80dB(A), and maximal subjective noise level. EEG signals were recorded for 60 seconds in each noise level. The power spectral analysis was performed to analyze EEG signal. At the same time, psychological stress was also measured subjectively by using a magnitude estimation method. The results showed that subjective stress and EEG spectrum indicated a statistically significant difference between noise levels. In particular, high level noise produced an increase in beta power at temporal(T3, T4) areas. It was also found that beta activity was highly correlated with subjective perception of discomfort, and subjects responded to car interior noise as arousing or negative stimuli. Moreover, beta power remained stable above 70dB(A), whereas subjective discomfort continued to increase even above 70dB(A) We concluded that brain waves could provide psychophysiological information of drivers emotional reaction to car interior noise. Thus, EEG parameters could be a new measure to determine optimal noise level in ergonomic workplace design after further verification in various experimental conditions.

• 소음진동
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• 제9권4호
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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.

• 소음진동
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• 제10권5호
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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.

• 한국정밀공학회지
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• 제25권12호
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• pp.117-124
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• 2008

In early design stage, the simulation of interior noise is useful for the enhancement of the noise, vibration and harshness (NVH) performance in a vehicle. The traditional transfer path analysis (TPA) technology cannot simulate the interior noise since it uses the experimental method. In order to solve this problem, in this paper, the hybrid TPA is developed as the novel approach. The hybrid TPA uses the simulated excitation force as the input force, which excites the flexible body of a car at the mount point, while the traditional TPA uses the measured force. This simulated force is obtained by numerical analysis for the FE (finite element) model of a powertrain. The interior noise is predicted by multiplying the simulated force by the vibro-acoustic transfer function (VATF) of the vehicle. The VATF is the acoustic response in the compartment of a car to the input force at the mount point of the powertrain in the flexible car body. The trend of the predicted interior noise based on the hybrid TPA very well corresponds to the measured interior noise, although there is some difference due to not only the experimental error and the simulation error but also the effect of the air-borne path.

• 소음진동
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• 제9권5호
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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.

• 한국음향학회지
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• 제32권4호
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• pp.329-334
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• 2013

자동차 엔진을 포함한 구동계 및 흡배기계 소음의 특징은 차수 스펙트럼(order spectrum) 분석으로 파악할 수 있다. 기존의 선행 연구에서는 엔진의 1차 및 2차 점화주파수(firing frequency)와 관련된 차수성분이 차실내부 소음에 주요한 영향을 미치는 것으로 알려져 있다. 본 연구에서는 차수스펙트럼의 변환에 따른 차실내부 소음의 음질(쾌적감) 차이를 파악하고자 한다. 이를 위하여 6실린더 및 4실린더 가솔린 엔진을 가진 승용차의 차실 내부 소음을 측정하고, 이 소음에 적응형 디지털 필터(adaptive digital filter)를 적용하여 차수레벨을 가감하는 방법으로 수정한다. 쌍비교법을 이용한 청음실험을 통하여 원음 및 편집음의 음질 정도를 평가하고, 음질 향상을 위한 차수스펙트럼 변화 방향을 제시한다. 결과적으로 반-차수(half-order) 성분의 차수레벨 감소가 차실내부 소음의 쾌적감 향상에 영향을 주는 반면, 점화차수 레벨의 감소가 항상 음질에 긍정적인 영향을 주는 것은 아님을 파악하였다.