• 한국음향학회지
• /
• 제23권4호
• /
• pp.309-315
• /
• 2004

본 연구에서는 가속주행소음 (pass-by noise) 시험을 측정할 때 차량 각 부분에서 발생하는 소음 기여율을 산정하고자, 그 선행연구로 정지 차량의 좌우 측면에서 음향 인텐시티 방법을 이용하여 근접 방사소음 특성을 연구하였다. 가속주행소음 측정구간의 엔진 회전수 대역인 2,800 rpm과 3,200 rpm으로 구분하여 시험차량 중심축 선을 기준으로 7.5m 떨어진 지점에서 음압을 측정하여 주파수별 지향특성을 해석하였다. 이 결과는 차량 소음 저감에 응용할 수 있다.

• 한국도로학회논문집
• /
• 제17권6호
• /
• pp.11-18
• /
• 2015

PURPOSES : The purpose of this thesis is to evaluate the effectiveness of an active noise cancellation (ANC) system in reducing the traffic noise level against frequencies from the predictive model developed by previous research. The predictive model is based on ISO 9613-2 standards using the Noble close proximity (NCPX) method and the pass-by method. This means that the use of these standards is a powerful tool for analyzing the traffic noise level because of the strengths of these methods. Traffic noise analysis was performed based on digital signal processing (DSP) for detecting traffic noise with the pass-by method at the test site. METHODS : There are several analysis methods, which are generally divided into three different types, available to evaluate traffic noise predictive models. The first method uses the classification standard of 12 vehicle types. The second method is based on a standard of four vehicle types. The third method is founded on 5 types of vehicles, which are different from the types used by the second method. This means that the second method not only consolidates 12 vehicle types into only four types, but also that the results of the noise analysis of the total traffic volume are reflected in a comparison analysis of the three types of methods. The constant percent bandwidth (CPB) analysis was used to identify the properties of different frequencies in the frequency analysis. A-weighting was applied to the DSP and to the transformation process from analog to digital signal. The root mean squared error (RMSE) was applied to compare and evaluate the predictive model results of the three analysis methods. RESULTS : The result derived from the third method, based on the classification standard of 5 vehicle types, shows the smallest values of RMSE and max and min error. However, it does not have the reduction properties of a predictive model. To evaluate the predictive model of an ANC system, a reduction analysis of the total sound pressure level (TSPL), dB(A), was conducted. As a result, the analysis based on the third method has the smallest value of RMSE and max error. The effect of traffic noise reduction was the greatest value of the types of analysis in this research. CONCLUSIONS : From the results of the error analysis, the application method for categorizing vehicle types related to the 12-vehicle classification based on previous research is appropriate to the ANC system. However, the performance of a predictive model on an ANC system is up to a value of traffic noise reduction. By the same token, the most appropriate method that influences the maximum reduction effect is found in the third method of traffic analysis. This method has a value of traffic noise reduction of 31.28 dB(A). In conclusion, research for detecting the friction noise between a tire and the road surface for the 12 vehicle types needs to be conducted to authentically demonstrate an ANC system in the Republic of Korea.

• 한국정밀공학회지
• /
• 제28권5호
• /
• pp.572-577
• /
• 2011

Curve squealing of inter-city railway vehicle is a noise with high acoustic pressure and rather narrow frequency spectra. This noise turns out to be very annoying for the people living in the neighborhood of locations and the passenger in railway vehicle where this phenomenon occurs. Squealing is caused by a self-exited stick-slip oscillation in the wheel-rail contact. Curve squeal noise of railway vehicles that passed by a factor of the speed limit, so to overcome in order to improve running performance is one of the largest technology. In the present paper, characteristic of squeal noise behavior at the Hanvit-200 tilting train test-site. Curve squealing of railway wheels/rail contact occurs in R400~ R800 curves with a frequency range of about 4~11 kHz. If the curve is less than the radius of wheel frail contact due to |left-right| noise level difference (dBA) shows a significant effect of squeal noise were more likely.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2005년도 추계학술대회 논문집
• /
• pp.789-792
• /
• 2005

The dominant noise sources of Diesel Multiple Units are powerpack, which is composed of engine, transmission and cooling system, noise and wheel-rail rolling noise. The interior noise of a running vehicle is determined by structure-borne noise and air-borne noise from these noise sources. The contributions of interior noise from each noise source are calculated by air-borne transfer functions and structure-borne transfer functions of noise sources. In this paper, source separation technique is proposed to determine these transfer functions from the results of stationary and running tests of existing vehicle. With this technique, it is possible to get hold of contributions of interior noise from .noise sources of running vehicle. This source separation technique makes it possible to take efficient measures for reduction of interior noise at the early car-development stage.

• Structural Engineering and Mechanics
• /
• 제57권1호
• /
• pp.21-43
• /
• 2016

A conditional probability based approach known as Particle Filter Method (PFM) is a powerful tool for system parameter identification. In this paper, PFM has been applied to identify the vehicle parameters based on response statistics of the bridge. The flexibility of vehicle model has been considered in the formulation of bridge-vehicle interaction dynamics. The random unevenness of bridge has been idealized as non homogeneous random process in space. The simulated response has been contaminated with artificial noise to reflect the field condition. The performance of the identification system has been examined for various measurement location, vehicle velocity, bridge surface roughness factor, noise level and assumption of prior probability density. Identified vehicle parameters are found reasonably accurate and reconstructed interactive force time history with identified parameters closely matches with the simulated results. The study also reveals that crude assumption of prior probability density function does not end up with an incorrect estimate of parameters except requiring longer time for the iterative process to converge.

• 한국소음진동공학회논문집
• /
• 제18권5호
• /
• pp.503-508
• /
• 2008

In this paper, various methods to improve the planetary gear noise in vehicles were introduced. Those cases of improvement have been used as good guidelines and references to prevent planetary noise problems. In this research, different types of planetary gear systems were also analyzed. The consequences of those analysis said in common that the planetary gear set generating noise mainly is the one which takes power directly from the turbine. Furthermore, a frequency versus vibration level map was introduced to judge how to solve the noise problem quickly in a vehicle development process. Besides, it is provided a predicting method which planetary gear set most contributes to noise problem taking in the vehicle and how to design the planetary gear set robustly.

• 한국소음진동공학회논문집
• /
• 제25권6호
• /
• pp.377-383
• /
• 2015

Torsion mode or bending mode of drive-line for rear-wheel drive vehicle exists in low frequency band. If resonance exists there between natural mode of driveline and powertrain excitation force, drive-line will manifest excessive vibration response. Also, the vibration response can be transmitted to vehicle body and can induce booming noise. A vehicle in this study exhibits a booming noise problem under specific transmission gear condition. To draw performance improvement plan, finite element analysis technique was used. Modification was evaluated qualitatively and priorities were derived. Finally, effectiveness of best modification was verified through test and full vehicle FE analysis.

• 전기학회논문지
• /
• 제58권7호
• /
• pp.1336-1341
• /
• 2009

In this paper, an EMI reduction effects using an EMC chamber is described and reduction methods is proposed. In the case of general electronic components a working frequency is low. But in this paper the vehicle cluster works 75MHz in the main clock frequency, becoming weak by noise because of being attached in TFT LCD. As the outer case installed in the vehicle is made up of plastic materials, the noise is radiated if not protecting noise in the PCB itself. Therefore, This paper will explain the theoretical basis and propriety with respect to the discussion and need about the guide for PCB design considering EMC, through the reduction of PCB noise.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.340-343
• /
• 2006

As the needs of consumer on ride comforts increase and the reduction of road traffic noise tightened step by step, the power unit noise emitted by cars has been reduced. It has been found that tire noise dominates noise produced by the power-train when vehicles are driven at high speeds. Therefore, in these days, tire/pavement noise is concerned. Tire/pavement noise is affected by pavement type and vehicle???s transmission loss. Tire noise mechanism is produced by several mechanisms. The sound of tire can propagate either through the air or through the structure of vehicle. Pattern noise is the result of pressure variations through the air to the interior side of vehicle. Especially, on smooth asphalt the periodicity of tread design, pitch sequence is important factor, which have an influence on the reduction of tire noise.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.125-129
• /
• 2003

The identification of location and strength distribution of extended noise sources is important in the practical noise control engineering, especially in the viewpoint of dealing with the inherent nature of noise problem in question. For noise source ranking inside an automotive vehicle, the window method has been mainly used due to its simplicity. However, time and cost drawbacks in the measurement and inaccuracy due to low-frequency tunneling and lack of phase information have been a serious problem in using this method. In this study, the inverse FRF method was employed to carry out the noise source ranking inside an automotive vehicle and it was also used to predict the interior sound pressure with the change of sound insulation materials. As a result, it was found that the source contribution of vehicle panels could be successfully identified in comparison with the window method. The sound pressure at driver's ear position was predicted based on the obtained data and was compared with the measured data. The agreement in spectral trends was acceptable and their difference in level was within 3㏈ above 500㎐.