CANTOR - EUROPA - TRIMIS | Transport Research...

Green Paper on Strategy of Research in Transport Noise page 1 of 28

Contract Number: TCA5-CT-2006-031331

Laboratoire Vibrations Acoustique

Institut National des Sciences Appliquées

69621 Villeurbanne France

email: [email protected]

CANTOR CoordinAting Noise TranspOrtation Research

and engineering solutions

D2.7 Green Paper on Strategy Plan

Project Coordinator: Marcus Wallenberg Laboratory for Sound and Vibration Research KTH Sweden

Partners: Chalmers (SE) KU Leuven (BE) KTH (SE) INSA (FR) ISVR (UK) TUBerlin (D) UFerrara (I)

Document identity : CANWP2TR1-281208-INSA05 Date : 2008-12-25 Level of confidentiality : Partners + Commission Written by Date (YY-MM-DD) Reviewed by Date (YY-MM-DD) Goran Pavić 08-12-27 Anders Nilsson 08-12-28


FOREWORD This Green Paper presents an outline of the research strategy on transport noise in Europe as perceived by the partners of the EU "CANTOR" Coordinating Action in Sustainable Surface Transport area. The overall aim of CANTOR is to engage experts from vehicle manufacturing industry, government agencies and research groups to focus on improved performance of transport systems with respect to noise. The work done so far on the project has identified a number of areas into which the future research in the transport domain should be focused. The present Paper outlines a strategy aimed at overcoming the current research shortcomings and better steering the future research toward the requirements of transport stakeholders. It is based on a survey of research needs identified by the partners within the project and on some complementary input from institutions not participating in the project. This project involves 7 university groups working in research on transport noise and an Advisory Board composed of 8 non-university institutions. CANTOR university members:

Marcus Wallenberg Laboratory, Royal Institute of Technology, Stockholm (coord.) Institute of Sound and Vibration Research, University of Southampton Department of Mechanical Engineering, Catholic University Leuven Institute of Technical Acoustics, Technical University Berlin Vibrations & Acoustics Laboratory, National Institute of Applied Science, Lyon Department of Applied Acoustics, Chalmers University of Technology, Gothenburg Department of Engineering, University of Ferrara

CANTOR Advisory Board:

German Federal Environment Agency French National Railways Akeryards Shipbuilding FIAT Research Centre Bombardier Trains Scania Trucks LMS International Müller-BBM


SUMMARY The survey of research needs done so far indicates that the whole of research activities covered by CANTOR partners are not of the same importance to the stakeholders. A few research areas should be given increased short-term priority. These areas are: wheel-rail interaction, tyre-road noise, passive noise control and lightweight structural design. The short-term priority areas should be accompanied by long-term priority ones: new passive material technologies, new active multifunctional solutions, globally optimised mechanical design by advanced computation and subjective noise perception criteria. The survey has also shown that large industries and operators working in transport rely on university research. However, the constraints on both sides make the quality and extent of collaboration lower than desired. The proposed EU research strategy on transport noise is divided into four components:

• Short term strategy: concentrate research activities and focus on a few areas which were identified to be of key priority: wheel-rail interaction, tyre-road noise, novel efficient passive solutions and optimised lightweight structural design. Make full use of Expert Groups for implementing the coordination of these research areas.

• Long-term base strategy: getting gradually involved into a multidisciplinary character

of future long-term research: novel passive material technologies and adapted active solutions integrated into multifunctional or hybrid designs. The links with research in adjacent technical areas should be initiated already during the project lifetime.

• Long-term strategy of information exchange: communication with stakeholders should

be brought to an efficient level and maintained on a regular basis. The closer links and regular communications with the EU Technology platforms should be established.

• Strategy of research implementation: future collective research work programmes

should be defined with the stakeholders including the mechanisms of supporting these programmes.


1. INTRODUCTORY COMMENTS ON EU TRANSPORT NOISE Noise is known to be one of the fastest growing pollutants in Europe. In urban and suburban areas, road traffic is one of the major noise sources. In the vicinity of roads the exposure to noise can be so strong that it may cause detrimental effects on health. The EU short-term target for the year 2010 is a noise reduction of 19 dB(A) for road traffic. The need for weight reduction as a mean to increase energy efficiency, both in the aerospace and in the automotive industry, makes it all the more a challenge to improve vibro-acoustic performance. Effective and efficient vibration and acoustic analysis, modelling, measurement and design methods are therefore essential to produce world-leading products and processes with good noise and vibration performance. The global warming problem is forcing the whole transportation industry to rethink the way the vehicles are conceived. The new powertrain concepts (electric, fuel cells, nitrogen, bio-fuels...) are not close enough to massive use in terms of price and performance. The next few decades will inevitably see a dominance of fossil fuel powered road vehicles and an increasing use of electric trains. The needed reduction of fuel/electricity consumption and emissions can be achieved only by reducing the weight of vehicles. This would have a direct impact on vehicle noise, both to the interior and exterior of vehicles. The new design concepts, technologies and materials have to be therefore developed by optimising the global vehicle performance, noise included. Noise and vibration performance is also an increasingly important design criterion, in a variety of industrial sectors, including the surface transportation industry: noise and vibration affect, or even determine, consumer choice as they are often perceived as an unconscious indicator of quality. A noisy vehicle will certainly be perceived as a low quality product, unless the noise is experienced as sporty, exciting, trendy, etc. Together with the ever more restrictive legal regulations regarding noise and vibration emissions and immissions, the increasing customer demand for vibro-acoustic comfort forces design engineers to take into account the vibro-acoustic behaviour of products and processes in their design. As such, noise and vibration engineering is of more and more concern to strengthen the competitiveness of EU industry, especially when compared to Asian industry where global quality, including noise and vibration performance, is much more a leading theme. Improved technologies are essential if the commitments of the Lisbon and Barcelona Summits, for world-leading industrial capabilities by 2010, are to be met. Sharp competition and development of computing technologies strongly affect the performance of transport industry. For example, during the last two decades the development time of cars has been drastically reduced from 100 to 36 months, mainly due to the application of high-performance computing in combination with advanced CAE tools. The current tools are responsible for reductions of 30 to 40% in development time and around 25 to 30% in cost. In order to further reduce the development time to a period of 18 months, innovative CAE tools are essential. When considering that the total development cost of one new vehicle is in the order of 1 billion euro, about 20% of which is spent on Noise, Vibration and Harshness (NVH) optimisation, even minor shifts of the costs to earlier phases and minor reductions of the development cycle will have a major financial implication. For example, eliminating 1 prototype test and refinement loop from the critical path corresponds to 12 to 20 days (out of 450). The direct cost element is also related to the reduction of the number of physical prototypes through more timely optimisations. With costs between 200 and 400 kilo-euro per prototype (depending on the vehicle model), in addition to test rig and manpower


costs, this impact is not insignificant and represents 20 to 30% of the total development costs. Since decisions made within the first 20% of the design cycle allocate up to 80% of the total production costs [1], an extensive and thorough design optimisation based on virtual prototypes is sought, preferably in the very early design stages, when physical prototype testing is prohibited. E.g. the development of a vehicle goes through several stages: the early conceptual design, the detailed design and analysis; the pre-production and finally the production. The cost of fixing a flaw which would affect the product’s competitive position, or even prevent its launch, will roughly rise tenfold by going from one stage to the next one. The need for an early inclusion of noise issue into the design process becomes essential. As stated above, the transport noise in the EU has to be reduced considerably. Further reduction of vehicle noise and further increase in the performance of protecting infrastructure, like noise barriers or soundproof facades, is getting increasingly difficult. The current solutions have already attained a fairly high level of efficiency. Any major improvements have therefore to involve either more radical solutions then the present ones or globally optimised designs. A successful control of transport noise relies on the knowledge and competencies of the personnel in charge, on the related tools in use and on the support supplied by exterior bodies. The university units involved in noise and vibration research can offer assistance in all of the three fields: by providing education in noise and vibration via under- and post-graduate programmes, short courses and workshops; by delivering tools which result from own research and finally by providing expertise in concrete cases. The way universities operate does not match the pattern of the industrial production process. The transfer of university research effort to EU industry suffers from inefficiency. As a rule, the universities have insufficient knowledge of real industrial needs and tend to pursue own research in independent way. In the other hand, industry has not an easy access to the information about this research, neither it has enough time to follow it. The objective of the EU Coordinated Action "CANTOR" is to improve the effectiveness of the EU research in transport noise through better coordination between the research bodies themselves and between the research bodies and the stakeholders.

2. RESEARCH STRATEGY OF CANTOR PROJECT The improvement of the effectiveness of EU research in transport noise is sought via a multitude of coherent future activities:

to coordinate the link between industry, government bodies and research groups to establish industrial and societal requirements in transport noise to provide and disseminate information on ongoing research in transport noise to formulate a research strategy to meet the future demands on transport noise control to improve the exchange of competencies via short-term personnel exchange to coordinate and market education programmes in transport noise to coordinate advanced short courses for employees of stakeholders to publicise and disseminate unclassified research information on transport noise to establish and display a catalogue of research facilities in transport noise.


The motivation for considering a strategy of future research in transport noise is twofold: 1. The evolution of objective factors linked to transport noise (such as increase in

transport flow, need to reduce the effects of global warming, requirements on energy saving, need for the greening of EU space and for improving the health of citizens) affects the priorities and timescales of the research on noise;

2. The un-coordinated and fragmented development of various noise control technologies at different European research centres calls for synchronised actions for improved efficiency, quality and applicability of results.

One of the key objectives of the project is the formulation of the future research strategy in transport noise in Europe. Several activities have been carried out within CANTOR aimed at drafting an outline of the research strategy. In particular:

Two meeting were held with the Advisory Board members at which the industrial and societal needs in the transport noise area were discussed.

A report has been published by the Project Coordinator describing the industry and society requirements in the transport noise area.

Basic steps of the 4-point research strategy plan were defined in a Preliminary strategy report.

Four questionnaires were circulated to get supplementary information by the partners, Advisory Board members and institutions outside the CANTOR consortium.

The research strategy outlined in the Paper takes into consideration several key elements:

need to carry out research in different areas of transport noise, expressed by industry and public authorities;

the state of research advancement in different areas and the formulation of short-term and long-term priorities;

policies of transferring the information and results of EU research in transport noise to the stakeholders;

activities to provide private and public finance for supporting the research in transport noise.

3. HOW IS COMMON RESEARCH ADDRESSED WITHIN CANTOR ? The research areas related to transport noise are divided in 5 application oriented fields: Tyre/Road Noise, Engine Noise, Flow Noise, Interior Noise and Wheel/Track & Ground Vibration) and 7 scientific fields (Numerical Methods, Statistical and Energy Techniques, Advanced Measurement Techniques, Active Control and Smart Materials, Sound Propagation Outdoors, Subjective Acoustics and Passive Control Techniques). The different application-oriented and scientific fields are assessed by the Expert Groups. The chairpersons of each of the Expert Groups serve as a link with the rest of the Consortium members and with transport noise stakeholders. The chairpersons are responsible for the coordination of the research activities within the field and, assisted by the Advisory Board, with the transfer issues from and to the Expert Group concerned. It is intended that the Expert Groups remain in activity after the termination of the project in 2009. The research partners have contacted several industrial groups in the transport area and have discussed the problems and the priorities among these. Based on these contacts and also considering future legislation, short term as well as long term needs have been identified.


4. THE EU RESEARCH NEEDS IN TRANSPORT NOISE At the time of writing of this Paper the Catalogue of Industry and Society Requirements has been already completed [2]. The priority research areas are listed below:

1. Improvement of tools for predicting internal and external noise 2. Determination of acoustic and dynamic properties of materials 3. Characterization of noise and vibration sources 4. Modelling of tyre-road noise 5. Modelling of wheel-track noise 6. Development of noise prediction tools for ships, underwater noise included 7. Founding of data bases for new materials 8. Modelling of aerodynamic noise.

A comparison of these areas with some recent research programmes has been made. Thus the research network "Quiet Traffic" of the German Federal Ministry of Education and Research, 2000-2006, has focused on the following priority subjects [3]:

Road Traffic Noise: • low-noise tyre design • sound absorbing road surfaces • optimised tyre - surface interaction • expansion joints (road-bridge transitions).

Rail Traffic Noise: • acoustic quality management • wheel-track interaction • braking noise: avoiding the high frequency squealing at low speed levels • ventilation system noise: reduction using an empiric model • HSG – high speed grinding

Effect of noise on humans has been stressed out (psychosocial effects / speech intelligibility & cognitive performance / noise-induced sleep disturbances) including an assessment of combined noises from different sources. The recommendation of the Working Group of Railway Noise of the EU Commission states that "noise reduction measures at the source should have priority", [3]. The same priority has been identified in CALM research strategy programme for quieter Europe [4]. Regarding rolling noise, being the most important source of railway noise, the priority should be to reduce the noise excitation [5]. Although the track grinding and maintenance have been identified as the prime measures to keep the existing rolling noise levels down, further studies of wheel-track interaction are needed to respond to one of the future priorities, the design of low noise tracks [6]. In the other hand, the already taken measures regarding the replacement of brakes are considered to have resolved the urgent braking noise problems. The tyre noise is considered as a major issue on the road noise side. The proposed indicative of the EC limit values for 2008 are already achieved by the majority of tyres currently on the market [7]. European Federation for Transport and Environment considers the current limits on tyre noise to be insufficient and has called for an overall reduction of at least 5 decibels [8].


The latest CALM II report on research priorities has identified several key areas to which the future EU research should be oriented, [9]. Regarding the emission-related research priorities, which form one of the two priority areas (the other being the perception related research):

Road noise: • Quiet road surfaces (priority: design, material, production technologies) • Low noise tyres (priority: optimisation of tyre/surface combination; other: new tyre

concepts) • Vehicle (priorities: idle and acceleration noise; exhaust and intake noise; thermal

management for more efficient encapsulation/shielding; other: lightweight structures, low noise engines and gearboxes).

Rail noise: • Rolling noise (priorities: retrofitting of cast iron blocks – under way; implementation

of K blocks – further research needed; special rail grinding technologies; maintenance; quieter vehicle and boogie design – new materials & shapes, damping, boogie shrouds; control of curve squeal).

• Brake noise (priority: brake screech) • Traction equipment noise (priorities: quiet diesel engines, auxiliaries noise – fans,

orifice noise – mufflers, active systems). Finally, the growing demand for energy savings puts pressure on new propulsion technologies for vehicles and on novel lightweight design of vehicle structures. All of this will no doubt have a considerable impact on vehicle noise. This calls for an additional research effort on new material technologies and on improved prediction tools as stated in [2].

5. THE RESEARCH NEEDS DEFINED BY CANTOR ADVISORY BOARD The five manufacturer/operator members of the Advisory Board of CANTOR have identified the priority research topics [10], see below: SNCF (railway noise): The operator like SNCF is responsible for the performance of the whole system rolling stock + infrastructure. Target research areas:

Noise sources: • Source characterisation (array measurements, simulation models, bench tests) • Solutions to develop (wheel dampers, skirts, auxiliaries, quiet disc brakes, ANC) • Applications (stations & depots, curve squeal, crossings & switches, new track

components, new track designs)

Noise propagation: • Phenomenology studies (weather effects, relief effects) • Solutions to develop (noise barriers with diffracting devices, new design of locations)

Annoyance: • Indicators (night, multi-exposure, health aspect, comfort).

Research on a number of these subjects is being carried out in collaboration with universities. Bombardier (railway noise):


Many of existing noise prediction tools are not reliable enough to allow for decision-making. The company needs: more systematic validation of prediction tools and results, knowledge of quality of simulations.

Target research areas: • Low weight & low noise design • Structure-borne noise prediction • Flow noise • Fan noise • Squeal • Brake screech

Akeryards (ship noise): Existing prediction tools developed by the company are found to be satisfactory for dealing with classical noise problems.

Future focus on: • Effects of underwater noise on marine life • Outdoor noise disturbance by cruise vessels in inner city harbours • Novel noise sources of unknown features (surf wave generators, levitation fans) • New solutions for weight and cost reduction (replacing classical materials) • Reduction of structure borne noise propagation from engines.

Scania (road noise):

Short-term noise problems: • Turbo whistling • Wind noise • Gear noise • Cooling fan noise • Oil pump excitation

Long-term noise problems: • New materials (absorptive & lightweight & strong) • Source localisation and characterisation • Computational aeroacoustics (external, in-duct, fans) • Global vehicle model (source ranking) • Integrated encapsulation (aerodynamics, cooling performance) • Combustion noise (identification) • Tyre noise • Low frequency noise – drowsiness (potential use of active control) • Compact low backpressure EAS.

CR Fiat (road noise): The NVH needs result from the future main requirements on vehicles: road noise exceeding powertrain noise, lighter vehicles, performance concern passive safety requirements, aiming at total recyclability.

Needs for internal noise research: • Optimal noise attenuation with passive means – understanding of energy transfer • Improving simulation tools for optimising damping and absorption • Exploit potential of ANC

Needs for internal noise research:


• Study of common solutions of car performance which affect noise • Reducing emissions at the source and shielding/encapsulating sources • Low noise / absorbing road surfaces.

6. IMPLICATIONS OF CANTOR RESEARCH A number of questions have been put to CANTOR partners related to the implications and scope of the research strategy to be formulated. The answers to this questionnaire are compiled below. The asterisks denote the degree of matching of responses. A summary of common views is listed below:

The research strategy should be formulated jointly between the partners, vehicle manufacturers, operators and specialised R&D institutions.

Once defined, the CANTOR research strategy should be presented to the EC, asking for further actions, and proposed to the EU Technology Platforms.

Providing the stakeholders in the transport area define some research priorities which are not within research competences of CANTOR consortium the partner(s) covering the given area is asked to include it in future plans.

EC is likely to further support research in transport noise via FP7 in response to future priorities proposed by CANTOR consortium

CANTOR partners could get industrial support via awareness / publicity of CANTOR activities.

Collaboration can be beneficial with Marie Curie EDSVS project and via joint activities with industry research.

7. IMPLEMENTING UNIVERSITY RESEARCH IN INDUSTRY It is well known that the US research is more efficient than that in the EU due to a higher level of resources and the closeness to industry and markets which are very responsive. In the US, the latter take the initiative of looking for research bodies while in Europe this goes the other way around. The technology of research transfer is very important for the success of research activities. There is no much point of well organising the research at the universities without having a clear perspective regarding the results. A series of questions was therefore put to the industry members of the Advisory Board in order to find out the practices of their companies with respect to the research subcontracting to external institutions. The responses are fairly encouraging, but it should be pointed out that the Advisory Board industry members are large companies which usually have the tradition of giving some parts of non-classified research away. It can be reasonably assumed that smaller companies, like subcontractors, involved in transport are less favourable to research in noise and thus to giving the parts of research to external institutions. Below is the summary of the common positions of the AB members concerned:

Desired research results on noise control lacking because of lack of available time. Research support needed from outside organisations. All companies rely on university research and consider it potentially beneficial.


Main objections to external research support: not applicative/involved enough. External research support mostly supposed to cover both missing competences and

workforce capacity. Hosting external specialist(s) during a length of time highly desired. The aspect of industrial innovation important in noise technology applications. Confidentiality is an issue to be rigorously respected, but it is not a prohibitive factor

concerning external research support. Turnkey solutions in noise control created outside the home organisation acceptable. No restrictions or constraints regarding the origin of the external organisation which

can provide research support (proximity desirable). Positive opinion about the potential of MSc / PhD research regarding typical industry

needs. Professional consultancies and university researchers can be both useful as partners. Research projects funded by the EC are as a rule a good way to obtain the desired

research result.

8. SCIENTIFIC AREAS RELEVANT FOR TRANSPORT INDUSTRY An independent survey has been made within CANTOR about the practices in dealing with transport noise issues. A number of related institutions, mostly German-based, were contacted. Although smaller fraction of the contacted institutions responded, the sample is representative enough to enable drawing some conclusions on the industrial practices. The responses were obtained by industrial companies: Robert Bosch GmbH, Bombardier, Eberspächer GmbH, Rieter Automotive Deutschland GmbH, Ingenieurgesellschaft Auto und Verkehr GmbH, Dr.-Ing. Prof. Starobinsky. Fahrzeug- und Flugzeugschalldämpfer / Pkw-Akustik, VM Motori S.p.A., Volvo Trucks, Rolls-Royce Sweden, Volkswagen AG and Volvo Penta and by two non-industrial institutions: Fraunhofer-Institit für Bauphysik and the University of Erlangen / Fluid Mechanics. The questionnaire concerned the seven scientific fields which define the scope of scientific research activities within CANTOR. The questions related to these fields were about the use of the existing tools (methods, techniques, procedures), about the needed but missing tools and about the relevance of the given scientific field for the activity of the company in the transport noise domain. The needed but missing applications were reported in two fields: numerical modelling and measurement. An inventory of these is given below: Missing numerical models: Missing advanced measurement techniques: Materials, joints, HF-structure borne sound, flow noise, structure borne sound radiation from mufflers, the range between low and mid frequencies, sound radiation index, gear forces with lubrication, cavitation noise.

Structure borne sound energy flow, air borne sound propagation inside exhaust systems with flow in realistic operating conditions, array measurement methods, measurements of forces, noise contribution ranking.

The issue of the relevance of different fields, specified by the industry, has produced quite an unexpected result which, given in terms of scored mean marks obtained from industry, is presented below:


Relevance of scientific fields in transport noise: interest dispersion of responses

The same charts excluding two research institutions, in spite of being similar in nature, show some indicative differences, see below. The similarity is misleading, being a consequence of small proportion of non-industrial institutions interviewed. These institutions taken on their own, where applicable, produced the ranking shown below.

Industry-evaluated relevance of scientific fields

It can be seen that the passive noise control is considered unanimously as a technology of prime importance, scoring 100%. This was found to be the only subject which has show no dispersion in responses of industry. Passive technology is believed to be safe and efficient in use. Furthermore it is backed by a large number of competing manufacturers. It is followed by the advanced measurement techniques, subjective noise assessment and numerical modelling. While the passive control technology provides key solutions to noise reduction, the areas of measurement/subjective/numerical aim at improving and optimising these solutions. The rather high importance attributed to these three fields means that the current solutions need further improvement. The pursuit of improvement goes first via the advances measurements which scores better than the numerical modelling, in spite of the latter being carried out more rapidly and at less expense. This implies that the industry is not entirely happy with the current performance of numerical models. The views on both of these subjects disperse quite significantly, as seen on the right-hand side chart, i.e. the dependence on measurement and on numerical computation in noise domain varies noticeably from one company to another. The rather high importance attributed by industry to the human response issue, which in the noise area corresponds to subjective noise assessment (noise quality), comes as no surprise. It is ranked by industry slightly above the numerical methods in spite of being still in the "discovery" stage. The interest in subjective noise assessment has risen notably during the last decade, being an outcome of the growing awareness that the current metrics in judging noise


annoyance is inadequate. The ranking of the subject has been fairly even across different industry sectors as seen by the associate low dispersion figure. In the other hand, the two praised approaches in the university world, the statistical energy techniques and the active control, are considered to have rather low relevance in current industrial applications. The statistical energy technique is believed to provide unreliable results and to miss depth and detail. This judgement is however not shared evenly by all, the spread in views is quite high. The active noise control, apart from being too costly, still needs to demonstrate its efficiency in ground/water transport applications. The conclusion about its limited applicability is shared fairly consistently, as seen by the low spread value. The subject about which the views diverge the most is the outdoor sound propagation. The outdoor propagation is not a preferred university topic, neither it is the priority topic in vehicle industry. Yet its importance for the field of transport noise is undeniable. The coordination of future research in EU university centres should take the present deficiency into account.

9. RANKING OF INDUSTRY NEEDS BY EXPERT GROUPS

The survey of relevance of different areas for industry, described in §8, has been made on a fairly small sample of companies. A complementary survey about the needs of transport industry has been made by the CANTOR Expert Groups. The objective of this survey was to identify the noise control tools and solutions in transport area already used by industry as well as the potentially applicable tools and solutions developed by academia but not used by industry. The proposals for the future development were created this way. The responses to survey questions have been first provided by the Expert Group members of CANTOR academic partners. These responses were compiled by the Expert Group Chairmen who have then made a synthesis of the survey topics. An abridged version of the synthesis is presented in Appendix. While the information provided by different Expert Group members about the current use of various noise control methods and technologies in industry applications were fairly coherent, the information about the potentially applicable tools actually in research stage show little coherence. As a consequence, the views about "what needs to be done" were often disparate. In a way all these discrepancies show the freedom of university research from commercial dictate. Nevertheless, a better inter-research coordination could be certainly useful, not so much to weaken the "blue-skies" research component, but rather to improve the research quality and thus its efficiency and penetrability. Clearly the transport industry uses and needs: a) methods of noise prediction allowing an easier analysis of response of complex structures during the design stage and an evaluation of noise propagation in urban and rural areas, b) efficient noise and vibration suppression technologies and c) alternative metrics for the assessment of noise impact on population. It targets optimised vehicles, track/road designs and infrastructure solutions which can provide satisfactory noise performance. It is expected that with enhanced next-generation CAE technologies, the solution of the


majority of noise and vibration problems can be shifted from the pre-production and production phases to the detailed design phase at the very least, representing an impact up to tens of millions of euros. In order to control the vibro-acoustic properties of products and processes in an efficient and economic way, either by effective design of the noise and vibration sources (primary control), or by optimal design of secondary control measures such as mufflers, absorbers, acoustic enclosures, etc., vibro-acoustic CAE tools have become indispensable in the product design cycle. In order for the numerical methods to become mature methodologies that provide accurate absolute noise and vibration level predictions over a wide frequency range within acceptable computational efforts, some major issues still need to be resolved through intensive research efforts. The classical numerical techniques, FEM and BEM, are considered satisfactory as a whole. Further development is needed in some areas, like modelling of joints or composite materials. The limitations of classical techniques to lower frequencies are inherent to these techniques and will not be removed by increasing the computation power. The dispersion of mechanical properties of industrial products and the impossibility to model assembly links fabricated by complex technology procedures require numerical approaches alternative to classical ones like fuzzy modelling. Statistical energy methods are presently the sole alternative to classical deterministic methods where higher frequencies are concerned. These methods will require a lot of improvement before attaining a safe level of industrial use. The improvements are needed on both the computation side and the user-friendliness side. The current research trends in the development of statistical energy methods indicate a promising outcome regarding the computation accuracy and robustness. However more effort should be oriented toward the transferability of the new results to the end users. The planned CANTOR training mechanisms could be used to help the transfer. Noise prediction by a unified approach seems not possible. Numerical methods applicable to lower frequencies and statistical methods applicable to high frequencies need to be complemented by methods which span the intermediary frequency range. This subject is common to many industrial fields, thus its further development will be assured in a ‘natural’ way. On-going research efforts to bridge the mid-frequency gap should be further focused to several promising approaches that can be grouped broadly into three types:

Efficient alternative deterministic methods which aim to stretch the low-frequency application range of conventional element-based methods, FEM and BEM, to higher frequencies; these methods include wave based and spectral methods, as well as techniques for enhanced numerical solver efficiency, advanced sub-structuring and domain decomposition techniques, and performance improvements such as fast multipole BE methods;

Energy methods which aim to improve and extend the frequency range of application of high-frequency probabilistic approaches such as SEA to lower frequencies;

Hybrid approaches that combine deterministic and energy methods. The existing tools for the prediction of outdoor noise propagation are believed to respond to the current needs to a globally satisfactory level. Improvements in outdoor noise propagation should be sought at the side of improved infrastructure noise control measures, like barriers, belts and vehicle skirts. The high ranking of advanced measurement techniques shows that measurements represent to industry an indispensable way of getting key information. Measurements can be considered as


a way to obtain information about unknown data, e.g. like sound absorption, but also to circumvent the need of relying on uncertain modelling by computation. The latter aspect much explains the interest for advanced techniques. Moreover, measurements represent the prime resource of a straightforward understanding of phenomena and of validations of results, which certainly is strongly appealing to industry. It is not surprising that even the methods considered as ‘complex’, e.g. acoustical holography, are used in industry. It is no less surprising that the list of methods used in academic research is large and contrasting. The CANTOR catalogue of measurement methods and equipment, already in construction, can become a valuable source of information to industry. The priorities in the development of advanced measurement techniques should include:

Characterisation techniques for sources of noise, vibration and pulsation. Air-borne source characterisation for the purpose of global noise prediction is a still unresolved issue. Surface-impedance and patch-impedance approaches should be adapted to industrial use. In the area of structure-borne characterisation the existing techniques have a pronounced academic character and need strong push towards applicability. The characterisation of pulsation sources has already attained industrial level in many important areas (fans, exhaust and intake systems…) and needs less priority than the other two fields. The exception is the aerodynamic noise characterisation which needs further development.

Measurement methods for specific applications (properties of resilient mounts at audio frequencies, properties of joints, material damping, flow noise, cavity absorption in vehicles…)

Advanced signal processing (non-planar acoustic holography, virtual source analysis, spectral conditioning, blind source separation, advanced beamforming…).

Regarding transport noise and vibration suppression technologies, applied either on vehicles, outdoors or in dwellings, the current emphasis is clearly on the side of passive solutions. The advantage of passive noise control is it safe operation (it never can go in a ‘wrong’ direction), the versatility of technologies available and (usually) moderate cost. For the time being the active control technology is lagging in performance from the operational and cost points of view. It should be recalled however that the active technology offers some potential advantages over the passive one, the most important of which is its superior low-frequency performance. Likely breakthroughs in sensor and actuator technology as well as in control function design could make the active control a viable solution in the area of ground and water transport noise. It can be expected that on the side of transport vehicles the emphasis will shift to acoustically and structurally optimised lightweight structures. In this respect, the development of novel composite and multifunctional materials with superior noise features represents a clear choice. The application of existing and future active control solutions to lightweight structures should be also a clear perspective providing the present feasibility issues are resolved. Both of these aspects, passive and active, require a multidisciplinary organisation of research because the sole competencies of acousticians are not sufficient to bring about the needed solutions. Novel passive designs can be potentially applicable to noise control at the source, such as wheel/rail and tyre/road control, but the opinions about the efficiency of such designs are not unanimous. Alternatively, the outdoor propagation paths could be treated by more efficient noise barriers and dampers of ground vibrations. While the control at the source is a clear recommendation, [3][4], the outdoor suppression measures are often inevitable.


The future developments in the domain of materials and technologies for transport noise and vibration control should be given the following priorities:

Lightweight composite structural elements (sheets, frames…) optimised for increased strength and low noise

Multifunctional materials of moderate-cost, incorporating noise suppression function, either passive (fillings) or active (distributed sensors/actuators)

Transfer to industry of novel material solutions already tested in research laboratories Improvement of vehicle noise control solutions (damped wheels, skirts, advanced

barriers…) More involved research in transport noise suppression away from the source.

The topic of subjective noise assessment is an area where the synergy between academic research, transport industry, noise agencies and public authorities is needed more than on any other topic. It is a paradox that the legislation sets precisely defined noise limits which have to be respected, while the LA/Leq metrics employed to measure the levels does not correspond to the reality of nuisances produced by transport noise. The most important point consists in convincing people in industry that they can move from their old metrics to new ones, which are more closely related to human perception (loudness, sharpness, tonality…). The effects of human vibration with respect to ride comfort and safety seems to be rather well understood and normalised. However, methods of predicting the relative importance of noise, vibration and thermal environments in vehicles and their combined effects need to be further elaborated.

10. THE GUIDELINES OF THE RESEARCH STRATEGY PLAN An initial framework of the research plan is outlined in [11]. A few research activities defined on the basis on presently known information, should represent the main short-term research priority. The applied fields of wheel-rail interaction, tyre-road noise, passive noise control and lightweight structural design seem to represent the principal interest of EU stakeholders involved in transport noise. This in turn puts the short term priorities at the scientific fields of passive control, advanced measurement techniques and numerical modelling. The core research activities should be concentrated, and focused on these few areas. Regarding the long-term strategy, the focus should shift from the dominantly vibroacoustic subjects to multidisciplinary ones, oriented towards the global greening of EU space. While the research units in partner institutions will continue to research on noise issues, one part of this work should be dedicated to gradually incorporating the (narrow) subject of vibroacoustic research into the (wider) subject of clean transport technologies. The research on transport noise, in particular the powertrain noise, should be brought closer to the areas of energy consumption, reduction of emissions, vehicle crashworthiness optimisation etc, all of which have an impact on noise. The development of composite materials with improved noise performance and of multifunctional materials incorporating active noise control becomes vital at this stage. In parallel there will be a need of numerical modelling of the dynamic behaviour of new materials. These new challenges go beyond the competences of dynamics and noise specialists. A novel, multidisciplinary organisation of research will be required, calling for collaboration between different teams. Such an organisation is not in the tradition of noise research specialists. The EC could provide much of the logistic infrastructure to this activity.


The university research is characterised by its upstream nature and the fairly wide freedom of choice of research subjects. The value of the work is expressed in terms of originality rather than final applicability. The major part of research effort never reaches any practical use, one of the reasons being that its potential applicability stays unknown to prospective users. This is why another aspect of long-term strategy should be developed: valorisation of research ideas and approaches including these which were not originally developed for the area of noise transport but which could well be exploited in the transport field. The valorisation should be done jointly with the representatives of stakeholders. The present Advisory Board of CANTOR is a good example of how the stakeholders’ valorisation panel should look like. The coordination aspect of transport noise research, defined in CANTOR, is limited to the exchange of existing research information between the partners themselves on one side and between the partners and the stakeholders on the other. This objective was fulfilled to a large extent already at the time of writing of this report. A new encounter is planned for January 2009 with a larger group of stakeholders. These exchanges during the project lifetime are supposed to clarify the content and the scope of future research activities which are of interest to all concerned. The question of continuing to support the research once the project is over will become a strategic one if the project is to remain credible.

11. THE RESEARCH STRATEGY PLAN OUTLINE Most of the future work is linked to the activities of the Expert Groups. These groups should remain operational after the termination of CANTOR project. The Expert Group chairpersons have assessed the state of research in the corresponding key areas. The collected information can serve as a good starting point, but should be constantly updated and broadened. The planned extension of Expert Group activities to research bodies and stakeholders exterior to the consortium did not take place at the time of writing of this report. This can be remedied in future times provided the partners decide to pursue CANTOR activities beyond the project closure date. A consolidated detailed list of research priority topics has been made, see Appendix. The Expert Group chairpersons should formulate action plans and have these plans approved by the Advisory Board. This report provides a framework of future research plans. The finalised list, to be delivered before the end of project, should contain:

a detailed schedule of urgent actions (short term plan) multidisciplinary research activities (long term plan) new research fields (long term plan).

The project programme addresses the key mechanisms of research sharing and dissemination: short term exchange of personnel, marketing and coordination of educational programmes, coordination of advanced short courses and publication of research results. Once the research priorities have been adopted, the collaboration and support activities need to be further elaborated. Three types of actions are of prime importance:

modalities of research sharing between the partners transfer of research added value to EU stakeholders


post-CANTOR position with respect to EU research programmes. The first action, the research sharing between the partners, is the one which has probably the most certain outcome. The short-term exchange of personnel can be organised either via the multi-partner projects or within the current EU Marie Curie scheme. The research transfer to the stakeholders, primarily to vehicle manufacturers and operators, is somewhat less certain. Already the Advisory Board members have identified the lack of available time and funding as the prime obstacle in fully carrying out the needed research. The dissemination of industry-friendly information via the project website will probably be a vital step toward a successful accomplishment of this action. This step is of strategic importance for the entire Coordination Action and its impact on the post-project continuation of research on transport noise. While the CANTOR partners have expressed the willingness to accept working on presently non-covered but needed research subjects within own competence, it is clear that such an involvement has to be accompanied by an adequate support scheme in order to become realisable. The support which the research on transport noise can obtain from the EC research programmes, either during or after the end of CANTOR project, is uncertain to a great deal. Such a support should not be considered as vital to the success of the project itself. The partners should however carefully explore the means of getting future research support on the identified priority subjects if the CANTOR project is to produce any concrete impact. This action should be well elaborated before the end of the project. The created mechanisms of information sharing using CANTOR website could remain in life after the project closure at a relatively low cost. In order to increase the efficiency of these mechanisms, a CANTOR ‘club’ could be founded. Industrial partners and stakeholders could join at a small fee and get an active access to the partners and other members. The fee would serve to cover the running costs of the club infrastructure. The access to the club would permit asking questions, giving suggestions and using unclassified research information generated by the present and future academic partners. Discussions, meetings and presentations of new research results could be organised using widely available internet contact procedures. The outline of the CANTOR research strategy can be summarised in the following:

Short term strategy: concentrate research activities and focus on a few areas of key interest: wheel-rail interaction, tyre-road noise, novel efficient passive solutions and optimised lightweight structural design. Specific techniques in demand, like noise source characterisation and composite materials modelling, should be improved. The partners working on these areas should build common research plans. Other partners who are not explicitly identifiable with these areas should contribute with specific inputs where such are applicable.

Long-term base strategy: getting gradually involved into a multidisciplinary character of future long-term research. This should include novel passive material technologies (new polymers, composite, micro-perforated…) and adapted active solutions integrated into multifunctional (smart sheets…) or hybrid designs (mounts, barriers...). The partners should establish links with researchers working in adjacent technical areas already during the CANTOR lifetime, starting with the identification of the overlapping technical domains and the ways the engineering data could be exchanged.


Long-term strategy of information exchange: an Advisory Board should be maintained in the post-CANTOR period to provide valorisation of research ideas and approaches which are potentially exploitable. The present Advisory Board could serve the purpose, but it could be enlarged by representatives of companies of different profiles, e.g. sub-contractors. The communication should be simplified, but maintained on a regular basis. The closer communications with the EU Technology platforms should be established.

Strategy of research implementation: the results of research coordination activities of CANTOR have defined the areas which are important for the stakeholders and need further research. The present consortium should pay therefore due attention to the policy of supporting the future research through contracts. The participation of the stakeholders in the current consortium and the individual contacts of the partners with the industry should be used to pave the way for future collective research work programmes and the modes of its finance on behalf of all interested sides.

12. REFERENCES [1] S. Thomke “Enlighted Experimentation: The New Imperative for Innovation”, Harvard

Business Review, 67-75, February 2001. [2] A.C. Nilsson "Preliminary report: requirements, activities and strategies", deliverable

D2.1, EU project TCA5-CT-2006- 031331 "CANTOR", March 2007. [3] P. J. Heinzelmann "Quiet traffic: goals and focus of research in Germany", InterNoise

2004, Prague, August 2004. [4] CALM Strategy Paper "Research for a quieter Europe in 2020". ISBN 3-200-00224-7,

Oct 2004. [5] "Position Paper on european strategies and priorities for railway noise abatement", EC

WG on Railway Noise, April 2003. [6] M. Jaecker-Cueppers "Rail noise and abatement strategies recommendations of the

Commission WG on railway noise", Brussels, May 2007. [7] FEHRL: Study SI2.408210 "Tyre/Road Noise", Volume 1: Final report, 2006. [8] T&E Bulletin: Commission prepares new rules on quieter and more energy-efficient

tyres. October, 2007. [9] CALM II Workshop, Brussels, October, 2007. [10] CANTOR: Presentations of Advisory Board end-user/operator Members at the project

meeting in Turin, May 2007. [11] G. Pavić "Preliminary report on strategy plan" deliverable D2.4, EU project TCA5-CT-

2006- 031331 "CANTOR", December 2007.


APPENDIX: EXPERT GROUP SURVEY – SUMMARY A1 Numerical methods in acoustics and vibration Numerical prediction techniques allow the evaluation of functional performance attributes, such as mechanical strength and stiffness, noise and vibration levels, durability, etc., at almost any stage of the design process. Both in the early design stages, dealing with concept performance optimisation, and in the verification stages which involve optimisation of the product functional performance, Computer Aided Engineering (CAE) tools have become indispensable for the development of high-quality products minimizing time-to-market. Since numerical methods are reducing the need for very expensive and time-consuming physical prototype testing, they stimulate cheaper and faster product launch. It is very clear that, in order to control the vibro-acoustic properties of products and processes in an efficient and economic way, either by effective design of the noise and vibration generating mechanisms themselves (primary control), or by optimal design of secondary control measures such as mufflers, absorbers, acoustic enclosures, etc., vibro- acoustic CAE tools have become indispensable in the product design cycle. Ideally, modelling and analysis tools would be applicable over the whole frequency range of interest, which is typically the audio-frequency range (ranging up to 20 kHz). In practice, specific methods are applicable in a limited frequency region. The main numerical prediction techniques for vibro-acoustic analysis are based on the finite element (FE) and boundary element (BE) methods. Due to the huge computational efforts involved with the element based techniques, their use is limited to the low-frequency range. Increasing computer power and various methods can ameliorate the situation somewhat, but the problem still remains. Full FE models of cars, for example, can be developed for frequencies up to a few hundred Hz, but the frequency range of interest spans some kHz. A related issue is that extremely large FE models produce extremely large quantities of output, so that it can be very difficult to make sensible design decisions. Finally, the presence of even small amounts of uncertainty and variability in the input data (mass, stiffness, dimensions etc) produce uncertainty and variability in response predictions that increase with frequency and must be taken into account. In summary, classical numerical methods encounter severe difficulties as frequency increases. At high frequencies there are very many modes and the vibrations can be described better perhaps in terms of waves which propagate through the structure. Energy methods come to the fore: the structure is regarded as being built up from interconnected component subsystems, each of which has many modes and the probabilistic response is given in terms of subsystem energy and the flow of energy through the structure. Foremost among such methods is statistical energy analysis (SEA). SEA runs into problems at lower frequencies, however, when the theory, assumptions and approximations behind SEA break down. In summary, SEA encounters severe difficulties as frequency decreases. There is therefore a “mid-frequency” gap in the modelling capabilities: too high for FE, too low for SEA. Unfortunately, this is typically the frequency range of highest human sensitivity to noise, and one that typically dominates subjective perception. Absolute prediction accuracy for noise and vibration levels in surface transportation vehicles


is largely dependent on the accurate modelling of the actual dynamic source loading of the considered systems, as well as on a proper representation of the various damping mechanisms. In this respect, some of the developed techniques not yet used in industry should be made available. Research-developed numerical techniques not used by transport industry:

Wave based methods Interface coupling approach Patch impedance technique Sound absorption (porous models, microperforated sheets)

Potentially applicable numerical techniques which need further development:

Detailed and accurate source models for the major vehicle noise sources (engine noise, tyre/road interaction, wheel/track rolling noise and vibration, exhaust noise, aerodynamic noise, powertrain noise) are needed to further reveal the source mechanisms as well as to provide efficient and representative dynamic loadings to system-level vehicle NVH models; to this end, major efforts are needed to couple CFD (Computational Fluid Dynamics) simulation methodologies to numerical approaches for acoustics and vibration in order to allow a proper analysis of flow- induced noise and vibration in, for instance, exhaust and intake components.

Noise and vibration damping in surface transportation vehicles typically arise from localised damping mechanisms in joints and connections, from multilayer trim components including novel lightweight structures, from microperforated and visco-elastic materials, ... Major research efforts are needed in order to include the (non-linear) effects of those damping treatments into vibro-acoustic vehicle system models in an accurate and efficient manner.

Probabilistic and possibilistic methods should be further developed in order to account for the aforementioned uncertainty and variability effects on the dynamic response variance. Both parametric as well as non-parametric approaches should be further investigated for their use in large vehicle NVH models.

Till now, numerical models disregard the human perception of noise and vibration levels. This calls for further research into sound quality evaluation and metric development as well as into auralisation techniques to allow to include objective as well as subjective noise and vibration evaluation in virtual numerical models.

A2 Statistical and energy techniques Out of several prediction approaches based on statistically averaged properties of vibration and noise, the Statistical Energy Analysis (SEA) has been considered as the most industrially-oriented one. Multiple constraints limit the use of the SEA. The method is used in industry as a basic prediction tool at high frequencies, but the results are often found to be unreliable. As a matter of fact, the quality of results produced by SEA largely depends on the fulfilment of its multiple constraining assumptions. As a result, the method is considered to be user-difficult and not reliable enough for decision making. Industry uses as a rule either one of the available commercial SEA packages, such as Auto-SEA, or some home developed software. All of these rely on classical SEA formulations. The university research has produced in last years some novel SEA formulations, more advanced and accurate than the classical one. The recent "hybrid" methods, which combine SEA and FEM approaches, have already demonstrated promising applicability.


SEA is mainly used in transport industry to predict noise inside vehicles: car, trains and ships. Some applications concern prediction of noise induced by turbulent boundary layers. SEA is unsuitable for outdoor noise applications. An energy-related approach, the intensity potential method, can be used in such applications. A derivative of SEA, the smooth energy method, has been used in large ship applications. Measurement of energy flow is a subject little known to industry. The existing methods used in academia require specialist knowledge and skills. Research-developed statistical and energy techniques not used by transport industry:

Hybrid SEA-deterministic approaches Statistical modal energy distribution analysis Wave based energy methods Heat equation analogy (intensity potential) Energy mobility method Measurement of structure-borne energy flow.

Potentially applicable statistical and energy techniques which need further development:

Definition of SEA sub-structuring rules SEA applications to systems of low modal density and strong coupling Improvement in the SEA calculation of coupling loss factors Improvement of SEA error estimates Development of energy-based source descriptors Energy approaches applied to composite structures Energy modelling of trim materials and fuzzy structures.

A3 Advanced measurement techniques and signals There exist a substantial amount of tools which are used. Measurement techniques using classical transducers are a lot in use. Beamforming techniques, laser vibrometry and acoustic near field holography are used for detailed investigations. In the field of road-tyre interaction the reciprocal pass-by noise measurement technique is gradually introduced in industrial use. Order analysis and modal analysis as well as transfer path analysis are standard techniques which use measurements. The 3-D roughness of road surface is investigated by optical methods. Measurements of sound absorption index of the road surface are also well known and used. With respect to engine noise the transfer path analysis is the most used method. Standard tools are sound intensity measurements, order analysis and modal analysis including contact free measurements with laser vibrometers. For the interior noise, classical transfer path/power flow analysis as well as scanning laser vibrometry has been applied with varying degree of success. Moreover experimental SEA is used with respect to interior noise. Also artificial head measurements as well as listening tests have been applied. Input power mapping using PU probes is used to weight different parts of the cabins housing in terms of sound sources. Standard tools comprise sound intensity measurements.


Regarding flow noise measurements have been reported employing 3d-high speed PIV (particle image velocimetry). Beamforming techniques, use of microphone arrays and acoustic cameras are also reported. Regarding wheel/track rolling noise and ground vibrations laser scans of track roughness are performed. Microphone arrays are used quite widely for identifying sources on moving trains. They are most effective for aerodynamic noise sources on high speed trains, but can also be used to identify noise from power units and auxiliaries. Wheel/rail contact forces are measured using load-measuring wheels. Also reported are measurement methods for dynamic stiffness of resilient elements including track fastening components. Research-developed advanced measurement techniques not used by transport industry:

Acoustic source quantification Tyre-on-tyre test; measurements of dynamic stiffness under load Spherical near field holography Virtual source analysis Spectral conditioning Blind source separation Measurement of dynamic properties of engine mounts Measurement of bending moments induced at coupling points Phase analysis for interior noise Measurement of energy flow across junctions Measurement of sea coupling loss factors PIV for flow measurements Excitation identification technique (RIFF).

Potentially applicable advanced measurement techniques which need further development:

Measurement characterization of joints and junctions between subsystems Measurement of the acoustical properties of interior surfaces Cylindrical near field holography. Dedicated acoustic source quantification for sound synthesis purposes Active two-port measurement techniques for flow noise. Improvement of transfer path analysis and methods for source characterization Structure-borne intensity Accurate loss factor measurements Scaling laws for sound transmission Comparison of laboratory and field measurements Measurements in hostile environments (inside combustion engines, in hot flows) Mapping of non-linear behaviour of mechanical systems Improved measurements of wheel/rail rolling noise using microphone arrays Quantification of source strengths from microphone array measurements Improved microphone array measurements for use with extended coherent sources.

A4 Active control techniques The most successful applications of active noise control are active headsets and active noise control systems for aircraft.


Active noise systems for the control of air-borne, structure borne, inlet and exhaust engine noise have been developed by many car and truck producers, although, up to now, very few systems have been introduced into the market. This situation is primarily due to the cost of the systems and the reluctance by the manufacturers of audio systems to incorporate active noise control technology in their products for vehicles. In the railway sector active control of diesel exhaust noise has been tested and some fundamental research has been carried out into the use of active control of squeal noise. There is also research work in progress to enhance the sound absorption properties of sound barriers used alongside railways or motorways by active means. In the marine sector prototype active mounting systems have been developed to reduce the noise transmitted by diesel engines to the hull and cabin compartments of small yachts. A number of reasons limit the applications of active noise control, such as effective control performance, weight, reliability, production cost, installation costs and maintenance costs, which are intimately connected between each other. The transducers used in active systems have complex designs which make them costly and prone to durability issues. Also, the control systems often rely on multi-channel controllers, which require expensive fast acting digital controllers and complex wiring systems to connect the sensors and actuators to the control unit. This introduces additional weight issues and more importantly installation and maintenance costs. The control performance of an active control system could be very efficient at low audio frequencies providing a large number of sensor and actuators is used in conjunction with a rather complex control unit. Thus simple prototype control systems developed up to now, which can partially withstand the cost, weight, durability, installation and maintenance issues produce only limited control performance. Moreover, these systems have been tested to vehicles already fully equipped with passive treatments which mask the effective performance of the active system. In order to address the problems mentioned above the research work should be carried out on the concurrent design of passive and active control measures. Reduction of vehicle weight is seen as a short term solution that would reduce both fuel consumption and exhaust pollution. Lightweight vehicles will have inherent noise problems, however, that should be solved with lightweight treatments. Active control may offer a valuable solution to this problem providing low-cost, robust sensor and actuators are developed. Complementary research is needed on the control algorithms and the technology for lightweight wireless communication between actuators in order to implement promising localised control solutions. It is believed that active noise control would be more appealing when combined with sound quality design and also when combined with audio systems. Similarly, combining vibration control with condition monitoring would provide better exploitation of sensors and actuators. Finally an area where it would be important to focus further research is the development of active control technology of tyre vibration and noise which would not conflict with the safety performance of the tyre. Research-developed active control techniques not used by transport industry:

Piezo-ceramic and electromagnetic devices Magneto rheological dampers Smart panels Active wheel suspensions.


Potentially applicable active control techniques which need further development:

Low cost, low weight, small size sensors and actuators Active barriers for traffic noise reduction Advanced control strategies of increased robustness and applicability Control schemes for sound quality engineering Active safety systems.

A5 Sound propagation outdoors The subject of outdoor sound propagation is particularly relevant for public organizations such as city councils, holder of infrastructures, e.g. roads and rails, as well consultancies working with different aspects of environmental noise. Vehicle industries (tyre/vehicle/train) feel little concerned with sound propagation outdoors. The only exception might be train manufacturers where some companies use in-house tools for predicting the effects of multiple sources on a train. There are numerous codes available for modeling sound propagation outdoors, but very difficult to classify. The application of these codes is not research driven but related to legislation and standards. This means they might even differ depending on the country where the activity takes place. Current tools are mostly considered by industry to be sufficient. The following codes where named: NORD 2000, SOUND PLAN, Ray tracing, CADNAX. The codes are used by consultancies and organizations concerned with environmental noise (also from traffic). In addition codes have been developed in the EC projects Harmonoise and Imagine, but it is not clear whether and how far these methods are applied. In the European Noise Directive (END) communities have been asked to create sound maps on which base later measures for noise control might take place. This sound mapping is carried out with the standard tools described above. However several deficiencies in the used methods have been discovered which partly could be covered by the existing competence at universities, partly however, indicate a further need of research. None of the standard tools are able to predict sufficiently accurate sound pressure levels and its variation (in time and space) in zones, which are not directly exposed to traffic noise (e.g. inner yards). Accurate input parameters collected in suitable way are often only available in a limited way. There are some methods available at universities, but there is a lack of transfer to engineering methods. The development of these methods is very unlikely to be industry driven, but is subject to the needs formulated by society. Research-developed methods for outdoor propagation not used by transport industry:

Predicting soundscapes in quiet/ screened zones inside urban areas Simplified methods taking into account the influence of meteorological parameters

(wind, temperature) Models describing the effects of turbulence on sound propagation.

Potentially applicable themes in outdoor propagation which need further development:

Quality of input data and its effect on the prediction accuracy Improved methods for describing ground attenuation


There is a need for developing better engineering tools Efficient time-domain prediction method for sound propagation in inhomogeneous

media applicable for high-speed trains, aero-plane jets and vehicle tyres Complementing existing numerical methods within computational aero acoustics and

general outdoor sound prediction tools Auralisation models to create virtual sounds in order to improve the link to annoyance Stronger link between soundscape properties and annoyance.

A6 Human factors Sound quality is rarely studied by manufacturers of railway vehicles as the ‘customer’ does not require it. On the contrary in the automotive field psychoacoustic tests for intelligibility and comfort inside cabins are currently carried out. Moreover tests by juries for evaluating the effects of some special noises and in general the quality of sound of the vehicle are frequently utilized. In the field of human response to vibration with respect to comfort the evaluation and assessment of vibration in cars and trains is conducted by measurements of motion at the interfaces with the body in translational and rotational axes, application of frequency weightings at 1-100 Hz and evaluation of RMS acceleration, RMQ acceleration, vibration dose value or mean comfort index. Moreover, assessment of dynamic properties of seats is conducted by measurement of the seat transmissibility and determination of SEAT values. The same type of analysis is carried out in ships, trains and cars for determining the effects of motion sickness. In buildings and closed spaces with respect to annoyance and disturbance the evaluation and assessment of vibration is determined by measurements of motion at the interfaces with the body, application of frequency weightings and evaluation of RMS acceleration or vibration dose value. Still some academic methods and procedures are not currently used in industry. A-weighted level is still widely used, instead of all its limitations which make it much less accurate than Zwicker loudness. Within this context several tests can be carried out inside cabins in order to measure impulse response and binaural responses. Results can be used to optimize the quality of the sound field inside the cabin by means of auralization tools. The most important point consists in convincing people in industry that they can move from their old metrics and procedures to new ones, which are more closely related to human perception. To this aim, tutorials and demonstrations could be proposed in order to convince people in industry that they can take advantage from the knowledge acquired from studies in psycho-acoustics. Research-developed human factors subjects not used by transport industry:

In cars and trains with respect to comfort frequency weightings for vibration and the analysis of vibration at the feet, hands and seat have been investigated at frequencies from 3 to 315 Hz. In ships, trains and cars with respect to motion sickness frequency weightings for low frequency motion in horizontal and rotational axes can be evaluated and methods of prediction of motion sickness from combined-axis motion could be utilized in the industry.


Among metrics proposed by psycho-acousticians, roughness still needs to be increased: none of the many existing models proved to be accurate when computed for real sounds (e.g. engine noise).

Methods of predicting the relative importance of noise, vibration and thermal environments in vehicles and their combined effects.

Potentially applicable human factors research which need further development:

Enhanced ASQ techniques dedicated for transport noise sound synthesis purposes Stable, fast and economic, in-situ inverse quantification methods Dedicated metrics for quantification and comparison of transportation noise Need for adequate sound synthesis methods to obtain controllable input-sounds for

jury testing Virtual PBN testing to investigate the impact of noise components on human

perception rather than db(A) and to include more complex acoustic environments (importance of road surface, noise barriers, buildings, vegetation, …)

Binaural synthesis methods Models of the relative importance and combined effects of motion, noise, and the

thermal environment in vehicles and the interactions between these environmental factors.

A7 Passive control techniques Passive noise reducing measures are extensively used by industry. Typical examples of passive means to reduce noise in vehicles are damping, trim panels, sound absorption, resilient mounting and shielding or encapsulation of main sources of sound. The effectiveness of many of these noise reducing measures is estimated based on experience. However, these empirical methods can not be used when a basic structure is changed or a new material is introduced. The supplier of materials used for passive noise control can often not give adequate information of the acoustic and dynamic performance of a product. For example, suppliers of resilient mounts typically give just the static stiffness of the mount. Even if the dynamic stiffness should be known as function of frequency and preload etc the end user does not necessarily have the knowledge to implement the data in any prediction scheme. Another example is the measurement of the loss factor of a beam with a damping layer. This is by many considered to be straight forward. The crucial task is to interpret the result to predict the effect of the same damping material when mounted on the floor of a car. Various ISO standards can make it possible to compare results measured in different laboratories. However the acoustic performance of a window is different when mounted in an ISO laboratory from its performance when mounted in say a train. In addition small samples used for testing perform differently than large samples. All these problems are common for most materials or components used for passive noise control. Testing procedures to simulate real mounting conditions must be developed and data bases for products and materials must be established. Prediction tools for making reliable parameter studies must be developed. In an energy-sensitive world there is a real need for new light-weight materials. The understanding of the acoustic and dynamic behaviour of composite and multi-layered sandwich materials must be improved. Numerical programmes like FEM, BEM and SEA are


extensively used by industry. Today these standard programmes can not be used for vehicles which are built of combination of composite materials and metal sheets. Procedures for incorporation for example frequency dependent material parameters in standard numerical codes should be developed. Some passive solutions developed in areas other than transport could be advantageously used. This includes novel polymers and multifunctional materials, metallic foams, micro-perforated sheets etc. Research-developed passive control techniques not used by transport industry:

Novel material solutions (polymers, metal foam, micro-perforated sheets etc) New wheel and tyre designs Coupling and joining of structures to increase losses Lightweight granular fills in hollow structures.

Potentially applicable passive control techniques which need further development:

Improved composite and other lightweight materials Passive solutions to reduce low frequency ground vibration Incorporating composite materials in standard fem and bem packages. Improved testing procedures and materials data bases.

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