Seungho Jang

Study on the Rolling Noise Model Using an Analysis of Wheel and Rail Vibration Characteristics

Rolling noise is an important source of noise from railways; it is caused by wheel and rail vibrations induced by acoustic roughness at the wheel/rail contact. To reduce rolling noise, it is necessary to have a reliable prediction model that can be used to investigate the effects of various parameters related to the rolling noise. This paper deals with modeling rolling noise from wheel and rail vibrations. In this study, the track is modeled as a discretely supported beam by regarding concrete slab tracks, and the wheel vibration is simulated by using the finite element method. The vertical and lateral wheel/rail contact forces are modeled using the linearized Hertzian contact theory, and then the vibration responses of the wheel and rail are calculated to predict the radiated noise. To validate the proposed model, a field measurement was carried out for a test vehicle. It was found that the predicted result agrees well with the measured one, showing similar behavior in the frequency range between 200 and 4000 Hz where the rolling noise is prominent.

Investigation of Noise Spectrum Characteristics for an Evaluation of Railway Noise Barriers

Most of the test methods used for determining the acoustic performance of the noise barriers in Korean standards address the sound-proof panels but refer to noise barriers as a whole system or their in-situ performances less. Many new types of trains with different operating speeds have been developed and produced, and civil appeals against railway noise are becoming quite extensive. Considering these latest changes of circumstances, it is necessary to investigate the current standards and specifications pertaining to railway noise barriers. In this paper, criteria for the measurements and evaluations of noise barriers and sound-proof panels are examined and experimental studies are introduced. In order to suggest more efficient methods for reasonable evaluations of the noise barriers, frequency spectrums of the noise source, the power of the actual railway vehicles, are investigated and introduced.

Characteristics of Vibration and Sound Radiated from Rails of Concrete Slab Tracks for Domestic High Speed Trains

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In the present paper, characteristics of rail vibration and radiated sound power from concrete slab tracks for domestic high speed train(KTX) is investigated by means of a numerical method. The waveguide finite element and boundary element are combined and applied for this analysis. The concrete slab track is modelled simply with a rail and rail pad regarding the concrete slab as a rigid ground. The wave types which contribute significantly to the rail vibration and radiated noise are identified in terms of the mobility and decay rates. In addition, the effect of the rail pad stiffness on the radiated power is examined for two different rail pad stiffnesses.

Comparison of Track Vibration Characteristics for Domestic Railway Tracks in the Aspect of Rolling Noise

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. The main contributors to rolling noise are the sleepers, rail, and wheels. In order to analyze and predict rolling noise, it is necessary to understand the vibrating behaviors of railway tracks, as well as of the wheels. In the present paper, theoretical modeling methods for railway track are reviewed in terms of rolling noise; these methods are applied for the three representative types of domestic railway tracks operated: the conventional ballasted track, KTX ballasted track and KTX concrete track. The characteristics of waves propagating along rails are investigated and compared among the types of tracks. The tracks are modeled as discretely supported Timoshenko beams and are compared in terms of the averaged squared amplitude of velocity, which is directly related to the sound radiation from the rails.

Study on the Noise Source Modeling and the Source Strength Estimation of Mugungwha Trains Running on the Conventional Railway

An accurate railway environmental noise prediction model is required to make the proper solution of the railway noise problems. In this paper, an engineering model for predicting the noise of conventional passenger cars is presented considering the acoustic source strength in octave-band frequencies and the propagation over grounds with varying surface properties. Since the formation of a train can be variable, the source strength of each locomotive and passenger car was estimated by measuring the pass-by noise and analysing the wheel-rail rolling noise. Some validation cases show on the average small differences between the predictions of the present model and the measurement results.

Radiation of rail noise regarding surface impedance of ground by using wavenumber domain finite and boundary element

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In conventional approaches to predicting rail noise, the rail is regarded as placed in a free space so that the reflection from the ground is not included. However, in order to predict rail noise close to the rail, the effect of the ground should be contained in the analysis. In this study the rail noise reflected from the ground is investigated using the wavenumber domain finite element and boundary element methods. First, two rail models, one using rail attached to the rigid ground and one using rail located above rigid ground, are considered and examined to determine the rigid ground effect in terms of the radiation efficiency. From this analysis, it was found that the two models give considerably different results, so that the distance between the rail and the ground is an important factor. Second, an impedance condition was set for the ground and the...

Numerical Analysis of Rail Noise Regarding Surface Impedance of Ground by Using Wavenumber Domain Finite and Boundary Elements

철도 차량이 궤도를 따라 주행할 때 발생하는 소음은 크게 전동 소음(rolling noise), 공력 소음(flow noise), 동력 소음(engine noise)으로 나눌 수 있다. 이 중 공력 소음은 차량이 250~300km/h 이상의 고속으로 주행할 때 주요 소음원으로 작용하며, 약 250km/h 이하의 주행 속도 구간에서는 전동 소음이 주요하게 발생한다[1]. 전동 소음에 기여하는 주요 소음원으로는 일반적인 자갈 도상 궤도(ballasted track)의 경우, 침목(sleeper), 레일, 그리고 차륜을 들 수 있다. 주파수 대역 별로는 대략 300~400Hz 이하의 저주파수 대역에서는 침목, 약 400~2000Hz 까지는 레일, 그리고 약 2000Hz 이상의 주파수 대역에서는 차륜에서 발생하는 소음이 지배적이다[1]. 특히 전동 소음에 대한 기여도 측면에서 볼 때, 레일 방사 소음이 가장 크게 기여하고 있으므로 전동 소음을 해석 및 저감하기 위해서는 레일 소음의 방사 특성에 대한 파악이 필요하다. Abstract An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In conventional approaches to predicting rail noise, the rail is regarded as placed in a free space so that the reflection from the ground is not included. However, in order to predict rail noise close to the rail, the effect of the ground should be contained in the analysis. In this study the rail noise reflected from the ground is investigated using the wavenumber domain finite element and boundary element methods. First, two rail models, one using rail attached to the rigid ground and one using rail located above rigid ground, are considered and examined to determine the rigid ground effect in terms of the radiation efficiency. From this analysis, it was found that the two models give considerably different results, so that the distance between the rail and the ground is an important factor. Second, an impedance condition was set for the ground and the effect of the ground impedance on the rail noise was evaluated for the two rail models.

Instantaneous Environmental Noise Simulation of High-speed Train by Quasi-stationary Analysis

An instantaneous environmental noise simulation method emitted by a moving high-speed train by quasi-stationary analysis is proposed in this study. In the method, the propagation attenuations from stationary point sources on segmented railways to a receiver are calculated using a general purpose environmental noise prediction program ENPro based on the ISO 9613-2 method. Then, the instantaneous environmental noise at a receiver due to a moving high-speed train considering convection effect is evaluated with the information on the propagation attenuations from the instantaneous train location to the receiver and the sound power levels and directivity of stationary point sources evaluated by German Schall 03 (2006). To demonstrate the validity of proposed method, simulated and measured time history of instantaneous noise for KTX-I and KTX-II on running are compared and the results show that the method can be utilized for the train noise source identification as well as the simulation of instantaneous environmental noise emitted by a high-speed train.