Noise and vibration engineering for the Railway SectorAILWAYSR
“Far better an approximate answer to the right question,which is often vague, than an exact answer to the wrongquestion, which can always be made precise.”John W. TukeyRight questions lead to right answers“I am not bound to swear allegiance to the dogmas of anymaster.”HoraceThe good thing of a problem without an obviousSolution is the pleasure in finding it“I support that symbiogenesis is the result of a long timecoexistence and that is the main source of evolutionarynovelty in all superior non-bacterian organisms.”Lynn MargulisFluent communication is the key to progress
Analyser FFT 32 channelsA WORK METHODMeasurements in Real TimeHistoryIngeniería para el Control del Ruido (ICR) is acompany located in Barcelona dedicated tosolving noise and vibrations problems. Foun-ded in 1995 by professionals with more than20 year of experience in the field of vibro-acoustics, ICR offers recent analysis methodsfor railways, automotive, wind power, indus-try and civil engineering sectors.The company’s goal has always been to offerthe right and most efficient solution for eachvibro-acoustic problem. To do so, most ofICR efforts have been focused on R+D, withthe objective to develop new predictive andanalysis methods.This company innovativeprofile has allowed ICR to take part in nume-rous highly technological projects, both natio-nal and international. In some cases, theseprojects were focused on a technology trans-fer from ICR to the main European rollingstock manufacturers.The company staff is formed by PhD, physi-cistsand engineers. This combined knowled-ge and experience allows the company toanalyze any vibro-acoustic problem from aglobal and specialized point of view. The re-sult is always a good diagnostic of the noiseand vibration problema and the proposal ofthe best solution.Solutions to noise and vibrationproblemsICR offers solutions to noise and problems ofits customers. This can be done either bysolving the problems once they are detected,or what is better, by trying to prevent andavoid them at the product design stage. Eve-ry problem receives an individual attentionand the best analysis options and proceedingalternatives are chosen for it. This includesthe use of standard engineering methods orthe use of ICR developed methods and analy-sis techniques.ICR includes acoustics studies, noise measu-rements, vibrations analysis, environmentalimpact studies, noise maps, software deve-lopment, acoustic insulation studies, acousticbarrier design, noise and vibration analysispaths, etc.ICR has up to 48 channels to measure noiseand vibrations simultaneously, with therequired accelerometers and microphones.All these elements analyse the signalaccording to the frequency and in real time— they can analyse spectra, transfer func-tions, coherence...The tests required in ICR can be performedeffectively with the goal of finding solutionsfor real problems of noise and vibration. Thisis possible thanks to the simultaneous con-trol of a large amount of measurementpoints.Our commitment is to always guarantee thebest solution for each vibro-acoustic prob-lem. The experience acquired working formore than 20 years has shown us that eachproblem of sound and vibration is unique andrequires a right answer. For this reason,large part of the company’s investments aremade in research and development in orderto always offer an efficient solution for yourproblem of noise and vibration.
Train vibroacoustic testICR success relies on five main points:• Our own prediction methods, based onreal operational conditions measure-ments, reduce the need for many theo-retical assumptions.• The ability to analyse both the airborneand the structure-borne noise contribu-tions. In addition to the noise sourcecontributions (Transmission Path Ana-lysis) we can quantify the noise andvibration transmission paths followedfrom the sources to each subsystem(Advanced Transmission Path Analy-sis).• Very short response time.• Really low prices.• Absolute transparency of the used con-cepts and methodology.The final result: a complete Know-How for thetrain manufacturer. Once introduced in theproduction process, it provides a very usefuland reliable knowledge database for the nexttrain generation.This is the way ICR proceeds. A detailed vi-broacoustic test is performed in a basis trainthat will serve as the starting point for thestudy of the new one. With the obtained re-sults we have all the necessary information topredict the new train’s acoustic behaviour.Numerical and analytical methods are thenused to evaluate any design modification in-volving materials and/or structural changes.How much noise radiates each panel?Once the test has been performed, we obtainthe noise contribution of each panel or sub-system (window, door, floor...) to one or seve-ral control microphones placed at any loca-tion (Passengers and Vestibule Sectors, Dri-ver Cab ...). The information is obtained forany desired train’s real time operational con-dition.This allows us to apply statistical methods tothe results. A statistical approach is impor-tant because many vibroacoustic inputs re-main unknown when making measurements(e.g. rail roughness or topography). Simpleapproaches commonly used for these inputsmay lead to noise prediction errors.Knowing each subsystem noisecontribution not only allows us to sortthe priorities of the modifications, butmay help to reduce themanufacturing cost.TRAIN VIBROACOUSTIC TESTFor any journey, we can also obtain the noisecontribution from the bogie connectionpoints to every control microphone. Informa-tion is given, as usual, for the whole audiblefrequency range.The train manufacturer is then able to decidethe convenience of modifying the bogie con-nection system.Moreover, he will be able to prioritise all ne-cessary changes on the basis of a clear nu-merical criterion, knowing the improvementobtained after each design modification. Thesame results can be given for any auxiliaryequipment connected to the coach.An example of structural excitation.
Evaluation of modificationsOnce all tests have been performed, we cancalculate by means of numerical and analyti-cal methods the noise changes that a designmodification will produce.For instance, as we know all panel contribu-tions for the initial basis train as well as thetransmission loss differences between the oldand new panels, we are able to calculate thepanel contributions in the new train.Once all contributions are added we can ob-tain the overall noise spectrum at any controlmicrophone for the new train.The result: a complete acoustic modelThe final result consists of a computationalacoustic model that includes:• All modifications considered in the newtrain project, as well as those sugges-ted by ICR.• The whole noise contributions of thenew train subsystems.• Active framework: it is possible to acti-vate/deactivate the modifications inorder to see their effect on the overallnoise.• New modifications can be introduced inthe model obtaining the correspondingnew noise values.In case of measurements being made for thetrain running inside a tunnel, and if free-fieldresults are needed for the new train (or vice-versa), a new model can be built to simulatethese circumstances. The new model is ba-sed on the calculus of the parietal noise diffe-rences between both cases.Which are the air-borne and structureborne noise contributions from eachpanel?We are able to distinguish between interiornoise air-borne and structure borne contribu-tions from each panel. i.e we can divide thenoise radiated from a panel into a structuralcomponent arising from the bogie and anaerial component from the parietal noisefield.Further informationThe results obtained from tests give us a lar-ge amount of information, which can be usedto verify the reliability of the used procedure.Among them:• Comparison between the overall dBAreconstructed SPL (Sound PressureLevel) and the measured one.• Comparison between the reconstructedspectra during a whole journey and themeasured one.• Comparison between the overall dBASPL and the structure-borne overallcontribution.As observed, we can perform a com-plete vibroacoustic test of the train.This allows us to quantify all soundsources as well as noise transmissionpaths. A very clear characterisation ofthe train vibroacoustic behaviour isthen obtained.As a final result we obtain: an interac-tive complete acoustic model of thetrain, which allows to see the effectsof any design modification.TRAIN VIBROACOUSTIC TESTExperimental setup.
ICR always use the most appropriate analysistools in order to solve a given problem andapplies the latest theoretical developments.This demands a continuous learning processin several areas, which allows us to constan-tly improve our predictions.At ICR we commonly make use of the latestdevelopments on.• Advanced Transmission Path• Analysis Finite Element Methods• Boundary Element Methods• Ray methods• Vibro-acoustic responses• Rolling noise prediction• Squeal noise prediction• Computational aeroacoustics• Statistical Energy AnalysisRolling and squeal noiseGiven the geometry of the wheels, rails, theirmaterials and some general train data, wecan calculate (for a specified wheel&railroughness spectrum level) the rail and wheelSWL (Sound Watt Level), and the SPL andequivalent SPL at any distance.After some measurements, we can calculatethe wheel dominant mode that controls thelimit cycle arisin from the wheel/rail non-linear interaction in curves. This generatesthe well-known problem of squeal noise.Tools and theory for completeanalysisTOOLS AND THEORY FOR COMPLETE ANALYSISNumerical methodsIn addition to analytical methods, numericalmethods are nowadays essential for vibroa-coustic predictions. Finite Element Methods(FEM), Boundary Element Methods (BEM)and Ray Methods are commonly used at ICRin order to preview vibroacoustic problems inthe design process of the train.The coach dynamic response to the motorand auxiliary equipment inputs can be eva-luated. Structural modifications can then beproposed and their effects computed. Thecorresponding noise radiation to the traininterior can also be calculated.The upper figure shows a coach dynamic res-ponse to a diesel engine supported by thelateral crossbars of the motor frame in nextfigure.Some data and computations for rolling noiseprediction. Noise prediction using a ray method.Motor frame.
ICR has incorporated the latest advances inCFD (Computational Fluid Dynamics) and isextending its abilities in order to performCAA (Computational Aeroacoustics) predic-tions. This is a quickly evolving computatio-nal field and reliable engineering CAA predic-tions were out of the scope of any computer afew years ago.However, the rapid advances in computatio-nal and numerical techniques allow us tostart addressing complex engineering pro-blems.ICR is able to make interior noise predictionsdue to the aerodynamic loading in high-speedtrains. The process is threefold: first, a FEM-CFD computation of the turbulent airflowaround the train surface is performed.The pressure surface distribution due to theaerodynamic loading is then obtained. Se-cond, the previous results are used as inputsof a FEM model of the train roof and/or fai-ring (laterals and floor can also be conside-red) and its dynamic response is evaluated.Finally, in the third step a BEM method, or anequivalent one, is used to predict the noiseradiated by the train roof vibration.The aerodynamic loading noise contributionis included in the train acoustic model andits effect can be compared with the contribu-tions of the train classical noise sources(rolling noise, motor, auxiliary equipment…).Computational fluid dynamics and com-putational aeroacousticsTOOLS AND THEORY COMPLETE ANALYSISOther ServicesICR offers many other services in the RailwaySector. Our aim is to cover all the project as-pects that may affect the vibroacoustic be-haviour of the train. These include (amongothers):• Subsuppliers pursuit for a guaranteethat the auxiliary equipment fulfils theproject’s technical noise and vibrationspecifications.• Main line guidance for material designtests.• Technical and scientific training onacoustics and vibrations.• Technology Transfer.• Acoustic environmental engineering.Pressure distribution over a train surfacePressure and velocity fields
: Noise and vibration path analysis of the different compontents which form the coach proto-type of the new AVE model of CAF, Construcciones y Auxiliar de Ferrocarriles.Consultancy engineering services in Alstom Transport Savigliano, Italy, for a 6 month pe-riod. Alstom Transport.Consultancy engineering services in Alstom Transport Belford, France, for a 18 month pe-riod. Alstom Transport.Consultancy engineering services in Alstom Transport Savigliano, Italy, for a 12 month pe-riod. Alstom Transport.Definition of the acoustic and vibration specifications for the equipments from external sup-pliers. Project: Chennai Metro. Consultancy engineering services in Alstom Transport SaoPaulo, Brazil. Alstom Transport.Aocustic study and protocol measurements of 4.000 (C4k), train units for NIR, North Ire-land Railways. CAF, Construcciones y Auxiliar de Ferrocarriles.Research project “EVS (Equipments Vibrations Specification)” design and development of anew tool for the specification of the maximiun noise and vibration levels of auxiliary equip-ment installed in trains . Alstom Transport.Transmission Path Analysis of the noise and vibrations of a prototype high speed train(AGV). Alstom Transport.Experimental tests of vibration in the power motor system of diesel units carried out in thelaboratory of Voith in Hamburg, Germany. CAF, Construcciones y Auxiliar de Ferrocarriles.Acoustic study and Transmission Path Analysis in a diesel 251 locomotive of Renfe.AtenasaSound pressure level measurements in the AVR 121 train in order to fulfil the noise regula-tion according to technical specifications as defined by Renfe and European regulations(ETI). CAF, Construcciones y Auxiliar de Ferrocarriles.Study of the influence of the flow separation and the pressure fluctuations beneath the tur-bulent boundary layer of the new generation high speed trains AGV (Automotrice à GrandeVitesse), France. Alstom Transport.Experimental Modal Analysis in the power motor system of diesel units ADR. CAF, Construc-ciones y Auxiliar de Ferrocarriles.Noise and vibration transmission path analysis in the Chamartín railway station. Solutionconsultancy. Ineco.Vibro-acoustic numerical model of train. Advice for air conditioning and verification meas-ures in Madrid Subway. CAF, Construcciones y Auxiliar de Ferrocarriles.Study of the influence of the non-stationary aerodynamic load on the noise levels inside thehigh speed train TAV-S104, Lanzaderas project. Spain. AlstomTransport.Transmission Path Analysis in the cabin of two diesel units model 333 and 334 of Vossloh.Atenasa.Stydy of the subsystem contributions at driver’s cab interior noise. Advanced TransmissionPath Analysis (direct transference approach). Barcelona Subway, Spain. CAF, Construc-ciones y Auxiliar de Ferrocarriles.Study of the sound pressure levels produced by the high speed line Vitoria - Bilbao - SanSebastián in Durango, Viscaya, when the train passes over the viaduct. Ineco.Noise and vibration engineering projectsBACKGROUND
BACKGROUND“META X: Advanced vibro-acoustic analysis in railways. The ATPA method” for AlstomTransport. The following tasks were carried out for this project:1. Development of the testing procedures to obtain the vibro-acoustics specifications ofthe different subsystems of any train (for both internal noise contributions and externalones with the train stationary).2. Evaluation of the interior noise contributions of all the different subsystems of the trainunder normal operating conditions3. Evaluation of the external noise contributions of all the different subsystems of thetrain for stationary operating conditions.4. Training: ICR trained Alstom employees in the application of the ATPA procedures.ATPA Technology transfer project for CAF, Construcciones y Auxiliar de Ferrocarriles. Thefollowing tasks were carried out for this project:1. Development of the testing procedures to obtain the vibro-acoustics specificationsof the different subsystems of any train (for internal noise contributions).2. Evaluation of the interior noise contributions of all train different subsystems undernormal operating conditions.3. Training: ICR trained CAF employees in the application of the ATPA procedures.Design of a silencer for the exit of foul air in the Rome Subway. CAF, Construcciones y Auxi-liar de Ferrocarriles.META W research project: advanced vibro-acoustic analysis in the railway industry. Newtechnologies and calculation methods. Alstom Transport.Complete acoustic study in the Xin Min Line train in China including ATPA testing of theVarsaw subway. Alstom Transport. The following tasks were carried out for this project:1. ATPA of a previous model of train (Varsaw subway).2. Implementation of modifications in the acoustic model of the new train.3. Interior and exterior noise forecast of the new train.4. Noise measurements according to client requirements.Complete acoustic study of the Nothern Spirit including ATPA testing of the Heathrow Ex-press, United Kingdom. CAF, Construcciones y Auxiliar de Ferrocarriles. The following taskswere carried out for this project:1. ATPA of a previous model of train (Heathrow Express).2. Implementation of modifications in the acoustic model of the new train.3. Interior and exterior noise forecast of the new train.4. Noise measurements according to client requirements.Cabin and intercommunication doors design. Xin Min Line Train, Rep. of China. Alstom-Transport.Complete acoustic study of the Diesel NIR (North Ireland Railways), UK. CAF, Construc-ciones y Auxiliar de Ferrocarriles.Control and monitoring of the vibrations produced by the works of the AVE in the section ofSagrera to Nus Trinitat in Barcelona. Acciona infraestructuras.