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07.01 Railroad & Ground-Borne Noise, Part 1

Development of a dynamic model of the axisymmetric railway wheel for sound radiation prediction
Time: 7:40 am

Author: Víctor Andrés

Abstract ID: 2385

In this work, a vibroacoustic model is developed to predict the dynamic response and sound radiation of an axisymmetric railway wheel under a non-axisymmetric excitation. To do this, first, the energy equation of the wheel is analytically integrated along the circumferential direction after an expansion of its response as Fourier series. Then, the vibrational dynamics of the three-dimensional wheel is solved through a set of two-dimensional problems which come from that integration. Subsequently, the three-dimensional sound radiation of the railway wheel is calculated from the solution of the aforementioned two-dimensional problems by means of analytical relations based on the harmonic distribution of the dynamics in the circumferential coordinate. Additionally, the wheel rotation is introduced in the model using an eulerian approach, in order to consider the associated gyroscopic and inertial effects. The proposed model presents a greater computational efficiency compared to full three-dimensional methodologies, without compromising the precision of the results. This allows the implementation of the sound radiation calculation in optimization algorithms with the aim of achieving quieter designs of railway wheels.

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TMD Tunable for Railway Groundborne Noise Control
Time: 6:00 am

Author: Wilson Ho

Abstract ID: 3136

Tuned mass rail dampers are cost effective for the mitigation of the airborne noise and vibration with the ability to be tuned for individual site. TMDs have been developed and installed at a single rail in a curve tunnel and achieve more than 4dB(A) noise reduction in many cases. According to the on-site noise reduction performance during damper installation, half, one, two or three dampers can be installed at each spacing between two baseplates. TMDs with only half-installation provides more than 10dB reduction at vertical pin-pin resonance (~1kHz). With the standard installation, they provide the strong damping to half the corrugation growth rate. The stick-slip phenomena which causes the corrugation will be affected by the damping effect from TMDs. On the other hand, they can also be tuned to the low-frequency (p2 resonance) for grandborne noise control. The high reduction of the grand borne noise proved our claim for effectiveness of the TMDs besides many other studies on the other parameters like the type of the baseplates or the soil types. According to the test results TMDs achieve strong performance in different range of the frequencies.

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Realizing a Self-powered Real-time Monitoring System on High-speed Trains
Time: 8:40 pm

Author: S.K. Lai

Abstract ID: 1476

The development of the worldwide high-speed rail network is expanding at a rapid pace, imposing great challenges on the operation safety. Recent advances in wireless communications and information technology can integrate the Internet of Things and cloud computing to form a real-time monitoring platform of high-speed trains. To realize this system, a sustainable power source is indispensable. In this case, an ideal solution is to deploy a vibration-based energy harvester instead of batteries for the electrical supply of wireless sensors/devices, as vibrations induced by rail/wheel contact forces and vehicle dynamics are an abundant energy source. To address this challenge, a multi-stable, broadband and tri-hybrid energy harvesting technique was recently proposed, which can work well under low-frequency, low-amplitude, and time-varying ambient sources. In this work, we will introduce our idea, following the recently proposed energy harvester and the dynamic responses of a train vehicle, to design a self-sustained sensing system on trains. Supported by this self-powered system, accelerometers and microphones deployed on an in-service train (in axle boxes/bogie frames) can measure vibration and noise data directly. The correlation of the vibration and noise data can then be analyzed simultaneously to identify the dynamic behavior (e.g., wheel defects) of a moving train.

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Use of a transient SEA for calculation of structure-borne interior noise in trains from an induction motor controlled by multi-mode PWM
Time: 8:20 pm

Author: Yosuke Tanabe

Abstract ID: 1582

This paper presents a transient SEA (Statistical Energy Analysis) approach to predict the structure-borne interior noise in trains from an induction motor controlled by multi-mode PWM (Pulse Width Modulation). Most of the induction motors installed in trains are controlled by multi-mode PWM, which switches between asynchronous and synchronous modes according to the speed to reduce switching losses. This control causes the electromagnetic forces of PWM harmonics to change, resulting in a transient interior noise depending on the vehicle's speed. In this paper, we model the bogie using FEM to calculate the transmission of the electromagnetic forces to the vehicle body through traction bars and dampers. Next, we model the vehicle body using a transient SEA to calculate transient energy in a 1/3 octave band excited by the transmitted electromagnetic forces. Finally, we restore the waveform of interior noise by applying the appropriate phase to the transient energy to auralize the analysis result. We obtained reasonable agreement by comparing the analysis results of the interior noise with the actual measurements.

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Rail noise grade separation alternative analysis case study
Time: 7:00 pm

Author: Paul Burge

Abstract ID: 2242

The San Francisco Bay Area has an existing commuter rail system that brings commuters from southern regional communities into the downtown city center.  One of the communities served by commuter rail service is the City of Palo Alto, CA, which includes four active grade crossings, each requiring train horn sounding for each train event.  The City wished to evaluate various options to eliminate the noise generated from horn soundings by creating road/rail grade separations at each existing grade crossing and other possible noise and vibration control elements.  The alternatives included crossing closures, rail bed trenching, viaducts, roadway underpasses, and tunnels.  A noise and vibration study was undertaken to provide an analysis of which alternatives would provide better reductions in noise and vibration in the surrounding community.  The study included an assessment of existing noise levels and predicted future noise and vibration levels for construction and operation of each proposed alternative using current established noise and vibration methodology.  The results of this study included comparisons of the noise and vibration associated with each of the of the proposed alternatives that could be used in conjunction with other studies considering cost, traffic, safety, aesthetics and other factors to select an overall preferred alternative.

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A case study on the noise effects of elevating existing train tracks
Time: 7:20 pm

Author: Joelle Suits

Abstract ID: 2381

When modeling rail noise on an elevated track, there are several adjustments that need to be considered relative to modeling at-grade operations. These adjustments include the effects of re-radiated noise from the track and support structure, reduced ground attenuation due to an elevated noise source and a reduction in the potential for shielding from adjacent rows of buildings.  These adjustments are built into the model as a part of the design of a project.  This case study examines a unique situation where a project involved elevating existing at-grade tracks to eliminate a bottleneck related to an at-grade crossing of two perpendicular train tracks.  The project elevated one main track over the other and shifted the track closer to noise sensitive receivers. The US Federal Transit Administration and Federal Railroad Administration guidance, which were used to assess noise impacts, produced unexpected results during the initial assessment due mainly to the assumptions regarding the changes in shielding and ground attenuation with the elevated structure.  This presentation will discuss the initial assumptions used in the project, the limitations of the model relative to changes in shielding and ground attenuation, and the solutions that were implemented to obtain reasonable results for the impact assessment.

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Effect of sound source movement at low Mach number on radiated noise level
Time: 8:00 pm


Abstract ID: 2503

Change in A-weighted sound pressure level or Noise level of radiated sound due to sound sources moving at low Mach number at the same speed along a straight track is discussed in this paper.  When a sound source move, frequency and amplitude modulation is observed in the radiated sound field.   Without their modulation, the noise level at a receiving point is determined only by distance and A-weighted sound power level of each sources.  Solution of modulated frequency and amplitude of radiated sound  can be obtained by using the Duhamel’s efficient calculation.  The modulated frequency and amplitude increase for approaching sources and decrease for receding sources.  The difference of maximum noise level,?and the equivalent sound level during the sources passing-by, with or without considering the modulation, increases monotonically with respect to source velocity, and independent of distance from the track.  This difference increases as dominant frequency band of the sources decreases due to A-weighting below 1 kHz.

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Cancer research lab, a challenging micro-vibration design
Time: 7:40 pm

Author: Siddharth Mahajan

Abstract ID: 3031

A donated land to three universities near a river bank, in an urban setting prompted the universities to commission a state-of-the-art cancer research lab for a prominent scientist. The site ambient vibration was measured around 2000 micro-inches/sec due to nearby highways, light-rail system, and long-term construction staging area, among others. The research lab requirements were dictated by high-end Scanning Electron Microscopes, Transmission Electron Microscopes, etc. The vibration specification for these tools demanded the environment to perform at or below 50 micro-inches/sec, a factor of 40 reduction. Typically, we desire the site ambient to lie below the vibration criterion with some margin to allow for contribution from building MEP sources. This unusual site condition presented on the surface, an impossible design challenge. We developed a multi-pronged design approach that took advantage of the soil condition at the site and designed a specialized foundation for the lab floor, and supplemented it with improvement on the tool-based isolation system by implementing an active isolation system. The final result was that the 40x site vibration was reduced to below lab vibration criterion curve of 50 micro-inches/sec. To our knowledge, the structural and foundation system of this lab is one-of-a-kind in the world.

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