Bsi bs en 15461 2008 + a1 2010 (2011)

BRITISH STANDARD Railway applications — Noise emission — Characterization of the dynamic properties of track selections for pass by noise measurements ICS 17.140.30; 45.080 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 15461:2008 +A1:2010 BS EN 15461:2008+A1:2010 National foreword This British Standard is the UK implementation of EN 15461:2008+A1:2010 It supersedes BS EN 15461:2008, which is withdrawn The start and finish of text introduced or altered by amendment is indicated in the text by tags Tags indicating changes to CEN text carry the number of the CEN amendment For example, text altered by CEN amendment A1 is indicated by !" The UK participation in its preparation was entrusted to Technical Committee EH/1/2, Transport noise ‘Normative’ - A (mandatory) requirement defined as an ‘expression in the content of a document conveying criteria to be fulfilled if compliance with the document is to be claimed and from which no deviation is permitted’ [CEN/CENELEC Internal Regulations, Part 3: Rules for the structure and drafting of European Standards (PNE-Rules)] ‘Informative’ - Information (not mandatory) intended to assist the understanding or use of the document Informative annexes shall not contain requirements, except as optional requirements (For example, a test method that is optional may contain requirements but there is no need to comply with these requirements to claim compliance with teh document.) A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2009 © BSI 2011 ISBN 978 580 70850 Amendments/corrigenda issued since publication Date Comments 31 January 2011 Implementation of CEN Amendment A1:2010 EUROPEAN STANDARD EN 15461:2008+A1 NORME EUROPÉENNE EUROPÄISCHE NORM November 2010 ICS 17.140.30; 93.100 Supersedes EN 15461:2008 English Version Railway applications - Noise emission - Characterisation of the dynamic properties of track sections for pass by noise measurements Applications ferroviaires - Emission sonore Caractérisation des propriétés dynamiques de sections de voie pour le mesurage du bruit au passage Bahnanwendungen - Schallemission - Charakterisierung der dynamischen Eigenschaften von Gleisabschnitten für Vorbeifahrtgeräuschmessungen This European Standard was approved by CEN on 28 December 2007 and includes Amendment approved by CEN on 28 September 2010 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 15461:2008+A1:2010: E BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Contents Page Foreword 3 Introduction 4 1 Scope 4 2 Normative references 4 3 Terms and definitions 5 4 Symbols and abbreviations 6 5 Principles 7 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Data acquisition .7 Selection of the test section 7 Position of the accelerometers 7 Assembly of the accelerometers 8 Excitation force 9 Acquisition system 9 Acquisition of the FRF 9 Set of measuring positions 9 Measurement data to be produced 12 7 Data processing 12 8 Acceptance criteria 13 9 9.1 9.2 Test report 13 General 13 Presentation of the track decay rates 13 Annex A (informative) Calculation of the decay rates 14 A.1 General 14 A.2 Calculation of the decay rates 14 Annex ZA (informative) !Relationship between this European Standard and the Essential Requirements of EU Directive 2008/57/EC of the European Parliament and of the Council of 17 June 2008 on the interoperability of the rail system within the Community (Recast)" " 16 Bibliography 18 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Foreword This document (EN 15461:2008+A1:2010) has been prepared by Technical Committee CEN/TC 256 “Railway applications”, the secretariat of which is held by DIN This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2011, and conflicting national standards shall be withdrawn at the latest by May 2011 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights This document includes Amendment 1, approved by CEN on 2010-09-28 This document supersedes EN 15461:2008 The start and finish of text introduced or altered by amendment is indicated in the text by tags ! " !This document has been prepared under a mandate given to CEN/CENELEC/ETSI by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive 2008/57/EC For relationship with EU Directive 2008/57/EC, see informative Annex ZA, which is an integral part of this document." According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Introduction The interaction between the wheels of a railway vehicle and the track during operation is translated by vibrations which, in movement, generate rolling noise The vibration response of the track structure determines the level of its sound contribution to this noise The method assumes that the vibration waves in the rail can be regarded as the superposition of two bending waves, one vertical and the other transverse, of the rail represented as a simple beam Although the track rail does not behave in this way over all the frequencies covered by the measurement, this simplification permits the "decay rates" to be measured for an estimation of the dynamic behaviour of the track which is one of the basic parameters influencing the generation of rolling noise Scope This European Standard specifies a method for characterizing the dynamic behaviour of the structure of a track relative to its contribution to the sound radiation associated with the rolling noise This European Standard describes a method for: a) acquiring data on mechanical frequency response functions on a track; b) processing measurement data in order to calculate an estimate of the vibration decay rates along the rails in an audible frequency range associated with the rolling noise; c) presenting this estimate for comparison with the lower limits of the decay rates It is applicable for evaluating the performance of sections of reference tracks for measuring railway vehicle noise within the framework of official approval tests The method is not applicable for characterizing the vibration behaviour of tracks on loadbearing structures such as bridges or embankments Normative references The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies EN 61260, Electroacoustics — Octave-band and fractional-octave-band filters (IEC 61260:1995) EN ISO 266, Acoustics — Normal frequencies (ISO 266:1997) EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:2005) ISO 2041, Vibration and shock — Vocabulary ISO 7626-1, Vibration and shock — Experimental determination of mechanical mobility — Part 1: Basic definitions and transducers BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) ISO 7626-5, Vibration and shock — Experimental determination of mechanical mobility – Part 5: Measurements using impact excitation with an exciter which is not attached to the structure Terms and definitions For the purposes of this European Standard, the following terms and definitions apply 3.1 frequency-response function (FRF) frequency-dependent ratio of the motor-response phasor to the phasor of the excitation force (see ISO 7626-1) NOTE In this document, the term also refers to the mean spectral amplitude of the FRF in the form of a one-third octave spectrum NOTE In this standard, the term frequency-response function (FRF) is used to refer generically either to accelerance (accelerometric response/excitation force) or to mobility (speed response/excitation force) The term is not used to refer to receptance (dynamic compliance) NOTE The FRF is generally calculated as the interspectrum ratio between the response and the force with the autospectrum This estimate of the FRF is called estimate H1 NOTE A set of FRF between a single excitation point and multiple response points or even between a single response point and multiple excitation points may be used In this standard, the case of a fixed accelerometer and a mobile instrumented excitation hammer is the easiest to implement 3.2 accelerance complex ratio of the acceleration at one point in a mechanical system to the force at the same point or at a different point during a single harmonic motion (see also ISO 7626-1 and ISO 2041) NOTE Accelerance is an FRF currently expressed as a narrow-band complex spectrum It is also used in this standard to express a one-third octave spectrum 3.3 mobility complex ratio of the speed at one point in a mechanical system to the force at the same point or at a different point during a single harmonic motion (see also ISO 7626-1 and ISO 2041) NOTE Mobility is an FRF currently expressed as a narrow-band complex spectrum It is also used in this standard to express a one-third octave spectrum 3.4 direct FRF, FRF at the point of application FRF for which the response is measured at the same position (as close as possible physically with an impact hammer and an accelerometer) and the same direction (see also ISO 7626-1) NOTE In this standard, the term refers both to force and response FRF in the vertical and transverse directions 3.5 transfer FRF FRF for which the response amplitude is measured at a different position to the force application point NOTE In order to define the FRF, the direction and position of the application force and the response should be mentioned BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) 3.6 decay rate on the track vibration amplitude decay rate of the vertical or transverse bending waves of the rail as a function of the distance along the rail NOTE It is represented by a one-third octave band spectrum of the values of the decay rate, expressed in decibels per metre (dB/m) representing the attenuation as a function of the distance 3.7 test section section of track specifically associated with a particular set of measurement data 3.8 accelerometer position fixed position of the accelerometer(s) for which a complete set of FRF measurements is taken 3.9 structural wave vibration wave that is propagated along the rail resulting in a deformation of the whole rail section NOTE For example, vertical and transverse bending waves of the rail behaving like a beam or waves that involve deformation modes in the cross-section of the rail propagating along the rail The vibration waves with wavelengths that are smaller than the rail cross-section dimensions, such as the Rayleigh ultrasonic waves or the shear or compression waves in the material are not covered in the definition associated with the subject of this standard 3.10 one third-octave band spectrum spectrum of the added squared values or the root mean squares of the FRF in each of the normal frequencies one-third octave band (see EN ISO 266) NOTE In this document, also refers to the speed and acceleration vibration spectrum, to the excitation effort spectrum, to the mobility and accelerance FRF spectrum and to the resulting decay rate 3.11 reference track section portion of track used to characterize the rail system noise emission performances that meet the requirements of the interoperability technical specifications from the railway interoperability directives NOTE These requirements cover the track vibration response via the track decay rate and the acoustic roughness level of the rail They are intended to ensure the reproducibility of the measurements 3.12 instrumented hammer instrument with an integrated force transducer for applying an excitation force to the structure Symbols and abbreviations x position along the track The reference position x0 = is situated at the measuring point of the direct FRF, dx differential operator over x, n number of measuring positions, ∆xn n interval, xmax position of the maximum distance considered along the track, th BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) A(xn) FRF at position xn along the track, β response amplitude decay constant, DR decay rate, FRF frequency-response function, FFT fast Fourier transform Principles The decay rates are determined on the basis of an FRF at the application point and a certain number of frequency-response function measurements relative to the position on the rail of the excitation force application point (transfer function) An instrumented hammer shall be used to excite the rail For the purpose of this standard, an accelerometer shall be fixed to the rail and the measurements shall be taken for various distances from the force application point in relation to it The full set of FRF shall be measured in the vertical and transverse directions The decay rates of the vertical and transverse bending waves as a function of the distance shall be calculated on the basis of this set of FRF measurements The stages of the test method are specified in the following subclauses 6.1 Data acquisition Selection of the test section The test section shall meet the following conditions: a) the constitution of the track shall be constant over the whole test section for all the parameters that could affect the decay rates These parameters include the rail cross-sections, the stiffness of the pad beneath the rail, the cant of the rails and the space between the sleepers; b) the test section shall be fitted with long welded rails Specifically, it shall not have any rail expansion joints 6.2 Position of the accelerometers Within the test section, each position to which the accelerometer is fixed to the rail shall satisfy the following conditions: a) it shall be located inside the test section, at least 20 m from the centre of the test section; b) it shall be located at the median point of a space between the sleepers; c) the accelerometer shall not be located close to rail supports in an unusual condition; in particular: 1) there shall be no pumping sleeper less than metres from the accelerometer position; 2) there shall be no missing or damaged fastening clip (or fastening of any other type, if necessary) on the supports directly adjacent to the measuring accelerometer position; 3) the accelerometer shall not be located less than m from a rail weld; BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) 4) the accelerometer shall not be located less than 40 m from a rail expansion joint Three measurements of the direct FRF shall be carried out at three potential accelerometer positions at least, compatible with the requirement of 6.2 c) If at least two of the FRF are similar, it can be regarded that these accelerometer positions are representative of the whole test section, and subsequently can be used for the rest of the measurements If no accelerometer position is found in the first set of potential positions, others shall be sought, and their direct FRF verified, until a set is identified that does comply NOTE If no accelerometer position is obtained with this procedure, it is probably because the structure of the test section is not sufficiently homogeneous to be characterized by a single decay rate spectrum Therefore, another test section should be sought 6.3 Assembly of the accelerometers The accelerometer(s) shall be fixed: a) in the vertical direction on a longitudinal axis of the rail, preferably on the rail head If this is not possible, it (they) should be fixed on the flange of the rail; b) in the transverse direction, on the outside face of the rail head The accelerometer(s) shall be kept on the rail (either directly with the adhesive, or by a suitable support stuck on) at the positions shown in Figure NOTE system It is preferable to insulate the rail transducer electrically in order to maintain the integrity of the measuring Key vertical force transverse force accelerometers Figure — Position of the accelerometers on the cross-section of the rail BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) 6.4 Excitation force A force pulse is applied to the rail head in the vertical and transverse directions with an instrumented hammer fitted with a tip of adequate rigidity to ensure a good quality measurement of the force and the response in a frequency range of interest NOTE A titanium tip with a light hammer is required in practice to obtain good quality measurements at the upper limits of the frequency band In most cases, it is suitable for the lower frequency band limits also On the other hand, a less stiff tip can produce better quality results for the low frequencies In the frequency band of interest, a good measuring technique only requires light taps with the hammer as it does not then damage the surface of the rail ISO 7626-5 specifies the conditions of use of the coherence functions to ensure good quality of the measured data 6.5 Acquisition system The acquisition system shall comprise: a) a spectrum analyser with two channels or more, or any equivalent numerical equipment for the digital acquisition and processing of the signals; b) an instrumented hammer, and c) an accelerometer with a suitable signal conditioning system Anti-aliasing filters shall be used prior to the numerical sampling of the signal NOTE Alternative equipment may be used for the analogue integration of the acceleration signal so as to acquire a speed signal on the analyser In this case, better quality of the measurement is obtained by recording the mobility (speed/force) rather than the accelerance (acceleration/force) A better signal-to-noise ratio in the low frequencies is obtained when the responses measured are very weak compared to those obtained in the high frequencies as the dynamic of the data prior to recording or numerical sampling is reduced The measuring equipment shall meet the requirements of EN ISO/IEC 17025 6.6 Acquisition of the FRF A set of FRF shall be measured for the response of the rail in the vertical direction based on a vertical force pulse and a second set for the transverse response of the rail with transverse excitation The FRF shall finally be expressed in the form of a one-third octave spectrum covering at least the frequency bands between 100 Hz and 000 Hz inclusively If analogue filters are used, they shall meet the requirements of EN 61260 The FRF shall be measured according to ISO 7626-5 The corresponding FRF measured may be accelerance or mobility; estimation or measurement of these cross terms (vertical force compared to transverse response or vice versa) is not necessary An average FRF of at least validated pulses shall be taken into account for each elementary FRF The quality of each FRF measured (reproducibility, linearity etc.) should be checked using its coherence function It is recommended recording the latter NOTE Most of the acquisition systems produce narrow-band data with constant frequency increments The increment of the frequencies measured, in Hz, is equal to the inverse of the length of the sample, in s, The length of the sample should be limited to the time required for the pulse to be reduced to the level of the background noise of the signal Therefore, the lowest frequency band is determined by the value of the increment of the spectrum frequency measured and the minimum number of lines to be included per one-third octave band (three should be used) 6.7 Set of measuring positions Each set of FRF shall contain response measurements at the accelerometer position corresponding to pulses produced on the rail for the set of excitation positions described in Figure The FRF measured may be accelerances (acceleration/force) or mobilities (velocity/force) BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Figure shows the network of excitation measuring points established as a function of the sleeper spacing (or of the spacing of the rail support points) If the track does not rest on a limited number of supports or periodic rail fastenings, the specified positions shall correspond to the theoretical spaces between sleepers of 0,6 m The measuring positions are distributed in several sets of qualified measurements: spot, near field, far field The position of index is linked to the median point of the first inter-sleeper space, called inter-sleeper space When the pulse is applied at this point (in practice, as close as possible to this point also), the direct FRF is measured Measurements in the near field shall be carried out by applying the pulse starting from the response measuring point situated at inter-sleeper space with an interval equal to a quarter of the inter-sleeper space up to inter-sleeper space 2, then from that with an interval corresponding to half the inter-sleeper space up to the middle of inter-sleeper space and then at each median inter-sleeper position up to inter-sleeper space Measurements in the far field shall be carried out by applying the pulse starting a distance of inter-sleeper space from the response measuring point on the outer inter-sleeper positions 10, 12, 16, 20, 24, 30, 36, 42, 48, 54, and 66, as shown in Figure The measurements shall be carried out at least to the point for which the response at all frequencies of the range becomes negligible relative to the direct FRF at the same frequency The difference between the response levels at the index measuring point and at the excitation point shall be at least 10 dB in each one-third octave band In the event of very low decay rates, measurements over greater distances beyond 66 sleepers may be necessary and shall be carried out 10 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Key a b hammer impact on the rail above the sleeper hammer impact on the rail between the sleepers c position of the accelerometer d Index of the inter-sleeper space Figure — Decay rate on the track: grid of positions of the excitation points relative to the fixed response point 11 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) The complete set of vertical and transverse FRF is required to calculate the decay rates The FRF shall be recorded in the form of one-third octave band spectra If conversion of the FRF spectra into one-third octave band spectra is done by post-processing, this shall be done by calculating the root mean square of the mobilities or accelerances for each one-third octave band between the lower and upper limit frequencies of the spectrum (see EN ISO 266) Given that the decay rates depend on the characteristics of the material comprising the pad beneath the rail, the rail temperature shall be recorded during the measurements The FRF shall be calculated and recorded for calculating the decay rates 6.8 Measurement data to be produced At least two complete sets of measurements shall be produced The following sets shall be measured either on the other rail or on the same rail for response measurement positions at least 10 m from each other Data processing The measured data shall be mobilities or accelerances, supplied in the form of one-third octave band spectra The decay rates in each one-third octave band shall be evaluated using the following formula: DR = 4,343 xmax A ( xn ) x =0 0) ∑ A(x (1) ∆x n DR is expressed in dB/m whereas ∆xn shall be expressed in m A minimum decay rate that can be measured for a specific value of xmax shall be estimated with the following formula: DRmin = 4,343 x max (2) The decay rates estimated with equation (1) shall be compared with the decay rate obtained with equation (2): if the value derived from equation (2) is greater than half the value of any of the one-third octave bands of the spectrum, the estimation of the decay rate shall be regarded as being unsuitable However, it may be used to estimate the upper limit of the actual value of the decay rate NOTE A value of xmax of approximately 40 m is generally suitable for evaluating a decay rate for most tracks On the other hand, some types of track, fitted with flexible attachment systems, have significantly lower decay rates in certain frequency bands These decay rates calculated as a function of the distance for each one-third octave frequency band should be verified by comparison with the theoretical values of the exponential decay curve in Annex A to which they correspond This comparison should be done graphically by tracing the theoretical spatial responses measured as a function of the distance for each one-third octave band NOTE It should be remembered that the decay rate represents a simplified equivalent decay compared to the more complex one associated with actual behaviour 12 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Acceptance criteria The process leads to the production of a maximum of two sets of two one-third octave band decay rate spectra (in each of the vertical and transverse directions) Within the context of approval by comparison with a lower (or upper) limit curve, none of the spectra produced shall be less (or exceed) the limit curve in any of the one-third octave bands for the criterion to be satisfied 9.1 Test report General The following elements shall be included in the test report:  the words "Test according to EN 15461";  the location of the test section by definition of the line and its kilometre reference point;  the precise position of the accelerometers used and the orientation of the network of excitation points relative to it;  the description of the rail section;  a description of the type of track, including if necessary the type of sleeper, the approximate thickness of the ballast, of the type of slab or other characteristic;  the description of the pad under the rail or its type and reference, and its origin;  the type of rail fastening or support ;  the temperature of the rail during the measurements;  the manufacturer, types and serial no or other means of identification of the accelerometers, impact hammers or spectrum analysers used The decay rates shall be supplied in a table of numerical values or be presented in graphical form as specified in 9.2, with the associated limit spectra 9.2 Presentation of the track decay rates The decay rates (vertical and transverse directions) shall be presented in graphical form, for a range of onethird octave band frequencies between 100 Hz and 000 Hz The rate shall be represented on the vertical axis, expressed in dB/m with a logarithmic scale between 0,01 dB/m and 100 dB/m The frequency shall be represented on a horizontal axis with equidistant divisions for each one-third octave frequency band The frequencies considered shall be the normal frequencies corresponding to the one-third octave intervals specified in EN ISO 266 The temperature of the rail at the moment of measurement shall be mentioned with the results 13 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Annex A (informative) Calculation of the decay rates A.1 General This Annex describes in more detail the calculation of the decay rates on the basis of the FRF A.2 Calculation of the decay rates If A(x) corresponds to the amplitude of an FRF in a one-third octave band at a point on the rail head at a distance of x, the power radiated by the rail is proportional to the FRF of the excitation of the wheel/rail contact, integrated along the length of the rail, multiplied by the vibration velocity at the wheel/rail ∞ contact ∫ A( x ) dx Assuming that the vertical and lateral waves in the rail decrease as a function of the A( x ) ≈ A( ) e − βx , where β is the constant decay of the response amplitude A β can be converted into a decay rate expressed in dB/m, DR, such that DR = 20 log10 (e β ) = 8,686 β in distance along the rail, then dB/m ∞ Then, ∫ A( x ) dx is expressed simply as a function of the decay rate of the vertical and lateral wave by the equation: ∞ ∫ A( x) d x = A( x = 0) ∞ ∫e −2 βx d x = A( x = 0) 2β (A.1) This shows the way in which the decay rate characterizes the radiation performances of a track structure by the expression of a value in dB/m in each one-third octave frequency band In principle, the decay rates can be estimated as a slope of the amplitude response curve in dB as a function of the distance x In practice, however, because of the simplifying assumption of a rail response, expressed as the superposition of a vertical bending wave and a transverse bending wave, the actual change in amplitude as a function of the distance differs by a simply exponential decrease In these conditions, it is preferable to evaluate the decay rate based on a direct estimation of the accumulated response: ∞ ∫ A( x) 2 nmax A( xn ) d x = ≈∑ ∆xn 2 β n=0 A( x0 ) A( x0 = 0) (A.2) where xn is one set of points at which the response is sampled and nmax is linked to the point at distance xmax which is the maximum measuring distance, and where the summation is carried out at the response measurement points with ∆xn corresponding to the interval between the points situated at half-distance between the measuring positions on either side of the excitation position The last distance interval ∆xmax, at position 14 xmax , shall be taken as symmetrical to position xmax The interval linked to A(x0=0) shall be BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) regarded from position x = to midway between this point and the adjacent point, as the integral expression implicitly assumes The decay rate in each one-third octave band may then be estimated with the formula: DR ≈ 4,343 nmax A( x n ) n=0 A( x0 ) ∑ (A.3) ∆x n It should be noted that a precise measurement of A(x0) is important as it appears as a constant factor in the summation Indeed, the direct FRF is the easiest to measure accurately This evaluation method is robust for the high decay rates, but may be subject to errors if the value of xmax used in practice cuts off the response in whatever one-third octave frequency band before an adequate decay has been taken into account in the summation up to n max , to ensure good approximation of the integral It should be noted that as the summation of equation (A.3) is determined by the decay of the first 10 dB of the response along the rail, it effectively estimates the initial decay of the waves in this range of decay values, rather than giving an equivalent weighting to the weakest response data, the worst possible of errors It is an advantage of the proposed method over calculations for curve smoothing which give identical weights for all the measured data In this method, only the significant contributions of the rail response on the sound radiation are used in the calculation 15 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Annex ZA (informative) !Relationship between this European Standard and the Essential Requirements of EU Directive 2008/57/EC of the European Parliament and of the Council of 17 June 2008 on the interoperability of the rail system within the Community (Recast) This European Standard has been prepared under a mandate given to CEN/CENELEC/ETSI by the European Commission and the European Free Trade Association to provide a means of conforming to Essential Requirements of the Directive 2008/57/EC1) Once this standard is cited in the Official Journal of the European Union under that Directive and has been implemented as a national standard in at least one Member State, compliance with the clauses of this standard given in Table ZA.1 for High Speed Rolling Stock and Table ZA.2 for Conventional Rail Noise confers, within the limits of the scope of this standard, a presumption of conformity with the corresponding Essential Requirements of that Directive and associated EFTA regulations Table ZA.1 — Correspondence between this European Standard, the HS TSI RST published in the OJEU dated 26 March 2008 and Directive 2008/57/EC Clause/ sub-clauses of this European Standard The whole standard is applicable Chapter/§/annexes of the TSI Characteristics of the subsystem 4.2 Functional and technical specification of the subsystem 4.2.6 Environmental conditions 4.2.6.5 Exterior noise 4.2.6.5.1 Introduction 4.2.6.5.4 Limits for pass-by noise Corresponding text, articles/§/annexes of the Directive 2008/57/EC Comments Annex III Essential requirements General requirements 1.4 Environmental protection 1.4.1, 1.4.4 Annex N Measuring Conditions for Noise N.1 Deviations from EN ISO 3095:2005 N.1.3 Pass by Noise N.1.4 Reference track for pass by noise N.2 Characterisation of the dynamic performance of the reference tracks 1) This Directive 2008/57/EC adopted on 17 June 2008 is a recast of the previous Directives 96/48/EC ‘Interoperability of the trans-European high-speed rail system’ and 2001/16/EC ‘Interoperability of the trans-European conventional rail system’ and revisions thereof by 2004/50/EC ‘Corrigendum to Directive 2004/50/EC of the European Parliament and of the Council of 29 April 2004 amending Council Directive 96/48/EC on the interoperability of the trans-European high-speed rail system and Directive 2001/16/EC of the European Parliament and of the Council on the interoperability of the transEuropean conventional rail system’ 16 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Table ZA.2 — Correspondence between this European Standard, the CR TSI Noise published in OJEU dated 23 December 2005 and Directive 2008/57/EC Clause/ sub-clauses of this European Standard Chapter/§/annexes of the TSI The whole standard is applicable Characteristics of the subsystem 4.2 Functional and technical specifications of the subsystem 4.2.1 Noise emitted by freight wagons 4.2.1.1 Limits for passby noise 4.2.2 Noise emitted by locomotives, multiple units and coaches 4.2.2.4 Limits for passby noise Corresponding text, articles/§/annexes of the Directive 2008/57/EC Comments Annex III Essential requirements General requirements 1.4 Environmental protection 1.4.1, 1.4.4 ANNEX A Measuring conditions A.1 Deviations from EN ISO 3095:2005 A.1.4 Reference track for pass-by noise A.2 Characterisation of the dynamic performances of the reference tracks A.2.1 Measurement procedure WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard." 17 BS EN 15461:2008+A1:2010 EN 15461:2008+A1:2010 (E) Bibliography  ERRI C163/RP 21 report "Modelling railway rolling noise Description of the TWINS model and validation of the model by comparison with experimental data"  D J Thompson, “Wheel-rail noise generation, Part 1”, Journal of sound and vibration 1993 161, pp 387– 400  D J Thompson, B Hemsworth, N Vincent, “Experimental Validation of the TWINS prediction program for rolling noise, Part Description of the model and method”, 1996, Journal of Sound and Vibration 193 pp 123 -135  D J Thompson, B Hemsworth, N Vincent, “Experimental Validation of the TWINS prediction program for rolling noise, Part 2: results”, 1996, Journal of Sound and Vibration 193, pp 137 - 147  P Fodiman, F Létourneaux, C J C Jones, “European standardization related to railway noise emission: new standards to assess the reference track performance”, Forum Acusticum 2005, Budapest, proceedings, pp 1189 - 1194  C J C Jones, D J Thompson, R Diehl, “The use of decay rates to analyze the performance of railway track in rolling noise generation”, Journal of Sound and Vibration 293, pp 485 - 495 18 This page deliberately set blank BS EN 15461:2008 +A1:2010 BSI - British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: +44 (0)20 8996 9000 Fax: +44 (0)20 8996 7400 BSI 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