SIST EN ISO 11688-1:2009
(Main)Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 1: Planning (ISO/TR 11688-1:1995)
Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 1: Planning (ISO/TR 11688-1:1995)
This International Technical Report is an aid to understanding the basic concepts of noise control in machinery and equipment. The recommended practice presented here is intended to assist the designer at any design stage to control the noise of the final product. Methodical development of products was chosen as a basis for the structure of this document (see Clause 4). The list of design rules given in this International Technical Report is not exhaustive. Other technical measures for reducing noise at the design stage may be used if their efficacy is identical or higher. To solve problems going beyond the scope of this International Technical Report, the designer can refer to
the bibliography in Annex D, which presents the general state of acoustic handbooks at the time of
publication. Furthermore, reference is made to the numerous technical publications dealing with acoustical problems.
Akustik - Richtlinien für die Konstruktion lärmarmer Maschinen und Geräte - Teil 1: Planung (ISO/TR 11688-1:1995)
Der Text von ISO/TR 11688-1:1995 wurde vom CEN als EN ISO 11688-1:2009 ohne irgendeine Abänderung genehmigt.
Acoustique - Pratique recommandée pour la conception de machines et d'équipements à bruit réduit - Partie 1: Planification (ISO/TR 11688-1:1995)
Akustika - Priporočila za konstruiranje tihih strojev in naprav - 1. del: Načrtovanje (ISO/TR 11688-1:1995)
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Akustik - Richtlinien für die Konstruktion lärmarmer Maschinen und Geräte - Teil 1: Planung (ISO/TR 11688-1:1995)Acoustique - Pratique recommandée pour la conception de machines et d'équipements à bruit réduit - Partie 1: Planification (ISO/TR 11688-1:1995)Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 1: Planning (ISO/TR 11688-1:1995)21.020Characteristics and design of machines, apparatus, equipment17.140.20Emisija hrupa naprav in opremeNoise emitted by machines and equipmentICS:Ta slovenski standard je istoveten z:EN ISO 11688-1:2009SIST EN ISO 11688-1:2009en01-november-2009SIST EN ISO 11688-1:2009SLOVENSKI
STANDARDSIST EN ISO 11688-1:1999/AC:2004SIST EN ISO 11688-1:19991DGRPHãþD
SIST EN ISO 11688-1:2009
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN ISO 11688-1August 2009ICS 17.140.20; 21.020Supersedes EN ISO 11688-1:1998
English VersionAcoustics - Recommended practice for the design of low-noisemachinery and equipment - Part 1: Planning (ISO/TR 11688-1:1995)Acoustique - Pratique recommandée pour la conception demachines et d'équipements à bruit réduit - Partie 1:Planification (ISO/TR 11688-1:1995)Akustik - Richtlinien für die Konstruktion lärmarmerMaschinen und Geräte - Teil 1: Planung (ISO/TR 11688-1:1995)This European Standard was approved by CEN on 3 August 2009.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, 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 STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre:
Avenue Marnix 17,
B-1000 Brussels© 2009 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 11688-1:2009: ESIST EN ISO 11688-1:2009
EN ISO 11688-1:2009 (E) 2 Contents Page Foreword .3Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 98/37/EC .4Annex ZB (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 2006/42/EC .5 SIST EN ISO 11688-1:2009
EN ISO 11688-1:2009 (E) 3 Foreword The text of ISO/TR 11688-1:1995 has been prepared by Technical Committee ISO/TC 43 “Acoustics” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 11688-1:2009 by Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by DS. 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 January 2010, and conflicting national standards shall be withdrawn at the latest by January 2010. 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 supersedes EN ISO 11688-1:1995. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EC Directives. For relationship with EC Directives, see informative Annexes ZA and ZB, which are integral parts 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, 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 the United Kingdom. Endorsement notice The text of ISO/TR 11688-1:1995 has been approved by CEN as a EN ISO 11688-1:2009 without any modification. SIST EN ISO 11688-1:2009
EN ISO 11688-1:2009 (E) 4
Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 98/37/EC This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association to provide a means of conforming to Essential Requirements of the New Approach Directive 98/37/EC, amended by 98/79/EC on machinery. Once this standard is cited in the Official Journal of the European Communities under that Directive and has been implemented as a national standard in at least one Member State, compliance with the normative clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity with the relevant Essential Requirements of that Directive and associated EFTA regulations. WARNING - Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard. SIST EN ISO 11688-1:2009
EN ISO 11688-1:2009 (E) 5 Annex ZB (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 2006/42/EC This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association to provide a means of conforming to Essential Requirements of the New Approach Directive 2006/42/EC on machinery. Once this standard is cited in the Official Journal of the European Communities under that Directive and has been implemented as a national standard in at least one Member State, compliance with the normative clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity with the relevant Essential Requirements of that Directive and associated EFTA regulations. WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard.
SIST EN ISO 11688-1:2009
SIST EN ISO 11688-1:2009
TECHNICAL REPORT IS0 TR 11688-l First edition 1995-03-I 5 Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 1: Planning Acoustique - Pratique recommandge pour la conception de machines et d’6quipements 2 bruit r6duit - Partie I: Planifica tion Reference number ISOfTR 17 688-1:1995(E) SIST EN ISO 11688-1:2009
IsO/TR 11688=1:1995(E) Contents Page I Scope . 1 2 References . 1 3 Definitions . 2 4 Methodical design and acoustic aspects . 4 5 Conceptual and detailed design . 5 6 Low-noise prototyping . 23 7 Final testing . 25 Annexes A Summary of design rules . 26 B Noise control requirements for design . 31 C Information to be reported . 34 D Bibliography . 36 0 IS0 1995 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case Postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii SIST EN ISO 11688-1:2009
0 IS0 ISO/TR 11688=1:1995(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the Internation Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The main task of technical committees is to prepare International Standards, but in exceptional circumstances a technical committee may propose the publication of a Technical Report of one of the following types: - type 1, when the required support cannot be obtained for the publication of an International Standard, despite repeated efforts; - type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard; - type 3, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example). Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful. lSO/TR 11688-1, which is a Technical Report of type 3, was prepared by Technical Committee lSO/rC 43, Acoustics, Subcommittee SC 1, Noise. IS0 11688 consists of the following parts, under the general title Acoustics - Recommended practice for the design of low-noise machinery and equipment: - Part “I: Planning [Technical Report] - Par? 2: Introduction into physics of low-noise design ,. III SIST EN ISO 11688-1:2009
ISO/TR 11688=1:1995(E) 0 IS0 Introduction This International Technical Report provides a guideline for the design of low-noise machinery. Most of the existing International Technical Reports prepared in ISO/TC 43/SC I specify methods for the measurement and/or evaluation of noise. The final objective of this International Technical Report, however, will be noise control in existing machinery and noise control at the design stage. It is important that non-acoustic engineers are engaged in noise control practice. It is of great importance for these engineers to have a basic knowledge of noise generation and propagation characteristics and to understand the basic principles of noise control measures. Hence, this International Technical Report also serves as an introduction into acoustical terms, and as a basis to the acquisition of further knowledge in noise control. It is strongly required to support the dissemination of the given here through standardisation. Such considerations have led to the preparation of Technical Reports in the area of noise control. design rules nternational SIST EN ISO 11688-1:2009
‘TECHNICAL REPORT @ IS0 ISO/TR 11688=1:1995(E1) Acoustics - Recommended practice for the design of low-noise machinery and equipment - Part 1: Planning 1 Scope This International Technical Report is an aid to understanding the basic concepts of noise control in machinery and equipment. The recommended practice presented here is intended to assist the designer at any design stage to control the noise of the final product. Methodical development of products was chosen as a basis for the structure of this document (see Clause 4). The list of design rules given in this International Technical Report is not exhaustive. Other technical measures for reducing noise at the design stage may be used if their efficacy is identical or higher. To solve problems going beyond the scope of this International Technical Report, the designer can refer to the bibliography in Annex D, which presents the general state of acoustic handbooks at the time of publication. Furthermore, reference is made to the numerous technical publications dealing with acoustical problems. 2 References IS0 3744:1994, Acoustics - Determination of sound power levels of noise sources using sound pressure - Engineering method in an essentially free field over a reflecting plane. IS0 3746:- ‘1, Acoustics - Determination of sound power levels of noise sources - Survey method employing an enveloping measurement surface over a reflecting plane. IS0 4871:- ‘), Acoustics - Declaration and verification of noise emission values of machinery and equipment. IS0 961 l:- ‘1, Acoustics - Characterization of sources of structure-borne sound with respect to the airborne sound radiation of connected structures - Measurement of velocity at the contact points of machinery when resiliently mounted. IS0 9614-l : 1994, Acoustics - Determination of sound power levels of noise sources using sound intensity - Part I: Measurement at discrete points. IS0 9614-Z:-? Acoustics - Determination of sound power levels of noise sources using sound intensity - Part 2: Measurement by scanning. 1) To be published. SIST EN ISO 11688-1:2009
ISO/TR 11688=1:1995(E) 0 IS0 IS0 11200:-'1, Acoustics - Noise emitted by machinery and equipment - Guidelines for the use of basic standards for the determination of emission sound pressure levels at the work station and at other specified positions. IS0 11689:-l), Acoustics - Systematic collection and comparison of noise-emission data for machinery and equipment. 3 Definitions For the purpose of this International Technical Report the following definitions apply: 3.7 3.2 3.3 3.4 3.5 3.6 3.7 38 . 3.9 3.70 3.77 Airborne, liquid-borne and structure-borne noise: Sound propagating through air, a liquid or a solid structure, respectively. Active noise components: Components of machinery, which generate noise. In many cases these are the power converting devices generating mechanical work from power resources, such as electrical, mechanical or magnetic energy, hydraulic pressure, internal forces, or friction. Other noise “components” may be regions with non-steady flow and contact surfaces between moving parts. Psssive noise components: Components which transmit noise generated by the active components; they do not contain noise sources but can be dominating radiators of noise. Typical passive components are structural parts and covering panels of machinery. Periodic noise: A noise event which is periodically repeated. Typical gear wheels and piston machines. It is characteristic for periodic spectrum. sources of periodic noise are noise that it exhibits a line Tonal noise: Noise which is dominated by one or several clearly distinguishable tone(s). Broad band noise: Noise generated by either single shocks, i.e. short duration pressure pulses or impacts, or by turbulence in an air or fluid flow. The characteristics of broad band noise are that the frequency analysis shows a continuous spectrum over a large frequency range. force excitation: The excitation force is independent of the properties of the excited structure; an example of this is the effect of a light and flexible source on a relatively stiff and heavy structure. velocity excitation: The excitation velocity is independent of the properties of the excited structure; an example of this is a light and flexible structure excited by a relatively massive source. Quasi-static response: Response of the machine at frequencies below the lowest resonant . frequency. Resonant response: Response in a frequency range of distinct resonances. Multi-resonant response: Response in a frequency range with many resonances. SIST EN ISO 11688-1:2009
0 IS0 ISO/TR 11688-1:1995(E) Design process Noise control Y ::: Requirements concerning :c 5 1. Clarification of task noise behaviour from x ::: ::: .:. ::: X .:. ::: :: - clarifying standards, standards, authorities .:. X - :;: :.: requirements, state of 4 :i: the art. . . - regulations of clients, state of the art, j ::: ::: ::: competition, sales argument ::: .:* :a: - list of specifications :> :.: ::: 1 - own experience ::: : j: x :;: :*: .> :*: .:. 3: :2 - search for solution principles - comparison of different concepts - selection of concept 1 1 / t - choice of dimensions, material . . . - comparison (calculation and modelling) / -stk;tion y detailed L 4. Prototyping - measurements on prototype - evaluation of noise behaviour - comparison with references -1 I Clearance for series Acoustical experience and knowledge for comparison of different solutions - acoustical rules - rough formulae - diagnosis information - experience and examples - literature, drawings - acoustical modelling and FEM - acoustic devices - source strengths of partial sources (airborne, structure-borne, liquid-borne) . . . Noise measurement and noise reduction using the prototype - analysis and modification - acoustical diagnosis -final testing - comparison with the requirements Fig. 1: Stages of the design procedure; support of design process by noise control methods SIST EN ISO 11688-1:2009
ISO/TR 11688-1:1995(E) 0 IS0 4 Methodical design and acoustic aspects Methodical design is an operational approach which makes use of information from a variety of disciplines, for example machine acoustics. This way a basis is set for achieving targets and making decisions in design and development. The design procedure can be divided into four phases (listed below) which are increasingly specific (see Fig. I). Increase of information from phase to phase makes it possible to sort alternative solutions with respect to specific design criteria such as low noise level. The phases of systematic design are: 1. Clarification of task: Make a list of requirements which is the controlling document for the whole design task. Include noise specifications in this list with reference to legislation, the state of the art, competitors’ products, client demand or the weighting of machine noise as a company sales argument. (See Annex B.) 2. Conceptional design: This phase of the design process concentrates mainly on achieving the desired objectives. Little information is available about the final product at this stage and the noise behaviour is often assessed by comparison to known designs. 3 . Design and detail: As the design and choice of individual components progress, quantitative estimates of noise behaviour can be made through the selection of design options. 4. Prototyping: Measurements on the prototype allow quantification of major noise sources and sound paths. This may indicate specific measures leading to design changes. Compliance with the requirements can be confirmed by measurements. The following procedure can be applied in each of the four phases described above. It is very important to follow the methodology of eliminating the most dominant noise problems in the earliest possible stage of design: The first step of the process is determining the major sources of noise in the machine and establishing a priority list or scheme (see 5.2). Once the major sources are recognised, a more detailed analysis of the noise mechanisms must be carried out (see 5.3). The next step is analysing and describing the direct radiation of noise from the sources to the receiving position(s), and the transmission through the structure to the radiating surfaces (see 5.4). The final step contributions is to analyse the radi to the sound pressure ation level from those surfaces and to determine the various at the receiving position(s). Evaluate which combination of noise control measures is optimal. In designing low-noise machinery one should try to identify the basic acoustic mechanisms involved by consideration of the causal chain (Fig. 2). All design processes have a recursive element. So at every phase a decision has to be made as to whether the next phase can be entered or whether previous steps shall be repeated. SIST EN ISO 11688-1:2009
0 IS0 ISO/TR 11688=1:1995(E) I Acoustical mechanism I I 1 Part of machinery 1 r- Generation I 1 Source 1 1 Transyission 1 I Radiation I 1 Path I 1 Surface 1 Fig. 2: Causal chain of noise generation An illustration of how the different noise mechanisms are connected is shown in Fig. 3. The first priority in noise control is to identify the source. Different types of sources are shown in the first and second ring with key words corresponding to the headlines of the following clauses. Once the source type is determined, transmission through the particular medium will take place as seen in the third ring. Finally the noise will radiate into free air or excite a structure. The figure can be used to show that every sound source has its own characteristics, its specific transmission path through the structure and excitation of the radiating surfaces. To control the noise from a machine with many different types of sources, it is necessary to analyse each noise source, transmission path and radiating surface on its own to be able to evaluate the relative importance. The next clause shows an example of such a machine. 5 Conceptual and detailed design 51 . General Since a design solution always comprises the choice of a physical operating principle and the choice of a functional system, it is possible to make the following general comments for the choice of design concepts. With a high degree of probability, the mode of operation with the lowest speed and acceleration will provide the best acoustic solution. For a given operational principle the noise from a machine can be reduced by altering the mass, stiffness and damping of the structure. Design parameters such as material, shape, position, number of elements, dimensions, structure and type of connections can have a large effect on the noise emission. If applied in the proper way such alterations may reduce the vibration and/or radiation of the machine. Steady flow of gases and liquids is quieter than unsteady flow. Both in the conceptual phase and in the detailed design, the procedure described in Clause 4 and elaborated further in the following clauses can be used for diagnosis and noise control measures. In the conceptual phase only rough estimates, common design rules or a comparison with existing solutions is possible. In the detailed design phase the results of detailed calculations, modelling and survey experiments can be applied. 5 SIST EN ISO 11688-1:2009
ISO/TR 11688=1:1995(E) 0 IS0 -%$.A -u!!Ak~v /Ii+ Fig 3: Basic model of noise generation in machines SIST EN ISO 11688-1:2009
0 IS0 ISO/TR 116884:1995(E) 52 . Basic steps 5.2.1 Acoustical modelling and ranking The noise behaviour in machinery with different noise sources can be visualised by an acoustic model of the machine (see Fig. 2). To elaborate this model, the designer must first divide the machine into active and passive noise components. The active and passive noise components may have the capability of generating, transmitting and radiating airborne, liquid-borne and structure-borne noise. Therefore it is necessary to analyse the noise components for these three types of noise. The purpose of subdividing the noise components is the identification of the dominating noise sources, transmission paths and radiating surfaces. Then the designer must analyse along which paths noise can be propagated. Structure-borne, liquid-borne and airborne sound paths shall be considered. Furthermore, possible direct radiation of airborne sound from the individual active components must be considered. Finally the sound radiating surfaces of the machine must be identified. When the most important noise sources with their transmission paths are identified, an analysis of the process parameters must be carried out. The dominant noise contributions have to be controlled first. It is recommended to control the sources first before dealing with transmission paths and the radiating surfaces. Severe noise problems can be caused by the coincidence of driving frequencies and resonances in the active and passive components. General design rules: Divide machine into active and passive noise components; Locate airborne, liquid-borne and structure-borne noise sources; Locate the airborne, liquid-borne and structure-borne sound paths; Locate the sound radiating surfaces; Identify the strongest contributions (sources, transmission paths, radiating surfaces). 5.2.2 Example The purpose carried out. of this example is to demonstrate how acoustic modelling and noise source ranking can be Fig. 4 shows a hydrostatic power pack having active noise components such as: electric motor, hydraulic pump and a valve. They are all connected to the reservoir in a closed circuit. 7 SIST EN ISO 11688-1:2009
ISO/TR 11688=1:1995(E) 0 IS0 1) Relief valve 2) Outlet tube (12 mm) 3) Reduction fitting (25 mm - 12 mm) 4) Pump 5) Vibration-isolated flange 6) Mounting flange 7) Cover 8) Vibration-isolated coupling 9) Electric motor 10) Reservoir Fig. 4: Hydrostatic power pack The power pack has active noise sources representing airborne, structure-borne and liquid-borne noise sources. To visualise the transmission of noise from the different noise sources in the machine a block diagram, Fig. 5, is drawn which in graphical form illustrates the noise mechanisms of the power pack. A list of the noise sources, paths and surfaces is shown in Tables 1 to 3 SIST EN ISO 11688-1:2009
0 IS0 ISO/TR 11688-1:1995(E) Active Noise Components Passive Noise Components Reservoir, tubes and machine structure Key . . lo Airborne noise @ ‘/ “& Liquid - borne noise Structure-borne noise 0 Fig. 5: Acoustical model of power pack 9 SIST EN ISO 11688-1:2009
ISO/TR 11688-1:1995(E) 0 IS0 II Component Source Key I I A Airborne noise + Major contributor S Structure-borne noise - Minor contributor L Liquid-borne noise Component Source A S L Electric motor Electric motor Magnetic field Magnetic field Fan Fan -I- -I- Unbalance Unbalance Hydraulic pump Hydraulic pump Pumping Pumping + + + + Unbalance Unbalance Relief valve Relief valve Flow restriction Flow restriction Valve instabilitv Valve instability Table 1: Hydrostatic power pack; noise sources Table 2: Hydrostatic power pack; transmission paths Key I I A Airborne noise + Major contributor S Structure-borne noise - Minor contributor L Liquid-borne noise Component Path A S Electric motor Mounting points + Shaft Hydraulic pump Mounting points + Shaft Fluid connections Relief valve Mounting points Fluid connections . Coupling Coupling elements + Tubes Steel tubes Fluid Reservoir Mounting points + Plates Fluid Table 3: Hydrostatic power pack; radiating surfaces Key I I A Airborne noise + Major contributor S Structure-borne noise - Minor contributor L Liquid-borne noise 1 Component Radiating surface A S Electric motor Housing + Hydraulic pump Housing Tubes Walls Reservoir Walls + L IO SIST EN ISO 11688-1:2009
0 IS0 ISO/TR 11688-1:1995(E) A number of experiments were carried out on the power pack to identify the different sources, paths and radiating surfaces concerning noise emission. The main results are shown in Table 4 as sound power measurements in a reverberant room. All experiments were done under the same operating conditions. Table 4: Hvdrostatic Dower Dack: effect of noise control measures I Power ‘pack noise control 1500 rpm; 180 bar All transmission paths are present as in Fig. 5, A separate frame supporting the motor and the hydraulic pump is suspended by vibration isolators on the reservoir lid, The reduction in structure-borne sound transmission to the reservoir/machine structure results in a small reduction in sound power. The motor and pump frame is decoupled from the reservoir, The connection from the pump to the valve is made with a 2 m long hydraulic hose. This step gives a further reduction of 3 dB due to the reduction of structure-borne transmission to the reservoir, The reservoir is removed from the reverberation room, eliminating the airborne radiation from it, This does not result in a further noise reduction, leadidng to the conclusion that the reservoir was already sufficiently decoupled in step 3. The hydraulic pump is mounted on a conical flange on the electric motor, which included a vibration isolator, The fan is taken off the electric motor, and watercooling is provided, This results in a reduction of 1 dB, Finally the electric motor is encapsulated to reduce the airborne noise radiated from its surface, L WA in dB 90 89 86 86 85 81 The conclusions from the experiments were as follows: The sound pressure level of the airborne noise radiated from the surface of the hydrostatic pump alone was 9 dB less than the sound power from the complete pack; The major noise sources were structure-borne and liquid-borne contributions from the hydrostatic pump; The dominan
...
SLOVENSKI STANDARD
kSIST FprEN ISO 11688-1:2009
01-junij-2009
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Acoustics - Recommended practice for the design of low-noise machinery and
equipment - Part 1: Planning (ISO/TR 11688-1:1995)
Akustik - Richtlinien für die Konstruktion lärmarmer Maschinen und Geräte - Teil 1:
Planung (ISO/TR 11688-1:1995)
Acoustique - Pratique recommandée pour la conception de machines et d'équipements à
bruit réduit - Partie 1: Planification (ISO/TR 11688-1:1995)
Ta slovenski standard je istoveten z: FprEN ISO 11688-1
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
21.020 =QDþLOQRVWLLQQDþUWRYDQMH Characteristics and design of
VWURMHYDSDUDWRYRSUHPH machines, apparatus,
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kSIST FprEN ISO 11688-1:2009 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST FprEN ISO 11688-1:2009
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kSIST FprEN ISO 11688-1:2009
EUROPEAN STANDARD
FINAL DRAFT
FprEN ISO 11688-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2009
ICS 17.140.20; 21.020 Will supersede EN ISO 11688-1:1998
English Version
Acoustics - Recommended practice for the design of low-noise
machinery and equipment - Part 1: Planning (ISO/TR 11688-
1:1995)
Acoustique - Pratique recommandée pour la conception de Akustik - Richtlinien für die Konstruktion lärmarmer
machines et d'équipements à bruit réduit - Partie 1: Maschinen und Geräte - Teil 1: Planung (ISO/TR 11688-
Planification (ISO/TR 11688-1:1995) 1:1995)
This draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the Technical
Committee CEN/TC 211.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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, 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.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprEN ISO 11688-1:2009: E
worldwide for CEN national Members.
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kSIST FprEN ISO 11688-1:2009
FprEN ISO 11688-1:2009 (E)
Contents Page
Foreword .3
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 98/37/EC .4
Annex ZB (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC .5
2
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kSIST FprEN ISO 11688-1:2009
FprEN ISO 11688-1:2009 (E)
Foreword
The text of ISO/TR 11688-1:1995 has been prepared by Technical Committee ISO/TC 43 “Acoustics” of the
International Organization for Standardization (ISO) and has been taken over as FprEN ISO 11688-1:2009 by
Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by DS.
This document is currently submitted to the Unique Acceptance Procedure.
This document will supersede EN ISO 11688-1:1995.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EC Directives.
For relationship with EC Directives, see informative Annexes ZA and ZB, which are integral parts of this
document.
Endorsement notice
The text of ISO/TR 11688-1:1995 has been approved by CEN as a FprEN ISO 11688-1:2009 without any
modification.
3
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kSIST FprEN ISO 11688-1:2009
FprEN ISO 11688-1:2009 (E)
Annex ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 98/37/EC
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association to provide a means of conforming to Essential Requirements of the
New Approach Directive 98/37/EC, amended by 98/79/EC on machinery.
Once this standard is cited in the Official Journal of the European Communities under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the normative
clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity
with the relevant Essential Requirements of that Directive and associated EFTA regulations.
WARNING - Other requirements and other EU Directives may be applicable to the product(s) falling within the
scope of this standard.
4
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kSIST FprEN ISO 11688-1:2009
FprEN ISO 11688-1:2009 (E)
Annex ZB
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association to provide a means of conforming to Essential Requirements of the
New Approach Directive 2006/42/EC on machinery.
Once this standard is cited in the Official Journal of the European Communities under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the normative
clauses of this standard confers, within the limits of the scope of this standard, a presumption of conformity
with the relevant Essential Requirements of that Directive and associated EFTA regulations.
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within
the scope of this standard.
5
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kSIST FprEN ISO 11688-1:2009
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kSIST FprEN ISO 11688-1:2009
IS0
TECHNICAL
TR 11688-l
REPORT
First edition
1995-03-I 5
- Recommended practice for
Acoustics
the design of low-noise machinery and
equipment -
Part 1:
Planning
Acoustique - Pratique recommandge pour la conception de machines et
d’6quipements 2 bruit r6duit -
Partie I: Planifica tion
Reference number
ISOfTR 17 688-1:1995(E)
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kSIST FprEN ISO 11688-1:2009
IsO/TR 11688=1:1995(E)
Page
Contents
1
I Scope .
1
2 References .
2
3 Definitions .
4 Methodical design and acoustic aspects . 4
5 Conceptual and detailed design . 5
6 Low-noise prototyping . 23
7 Final testing . 25
Annexes
A Summary of design rules . 26
B Noise control requirements for design . 31
C Information to be reported . 34
D Bibliography . 36
0 IS0 1995
All rights reserved. Unless otherwise specified, no part of this publication may be
reproduced or utilized in any form or by any means, electronic or mechanical, including
photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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kSIST FprEN ISO 11688-1:2009
ISO/TR 11688=1:1995(E)
0 IS0
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, govern-
mental and non-governmental, in liaison with ISO, also take part in the
work. IS0 collaborates closely with the Internation Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International
Standards, but in exceptional circumstances a technical committee may
propose the publication of a Technical Report of one of the following
types:
- type 1, when the required support cannot be obtained for the
publication of an International Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or
where for any other reason there is the future but not immediate
possibility of an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International
Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three
years of publication, to decide whether they can be transformed into
International Standards. Technical Reports of type 3 do not necessarily
have to be reviewed until the data they provide are considered to be no
longer valid or useful.
lSO/TR 11688-1, which is a Technical Report of type 3, was prepared by
Technical Committee lSO/rC 43, Acoustics, Subcommittee SC 1, Noise.
IS0 11688 consists of the following parts, under the general title
Acoustics - Recommended practice for the design of low-noise
machinery and equipment:
- Part “I: Planning
[Technical Report]
- Par? 2: Introduction into physics of low-noise design
,.
III
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kSIST FprEN ISO 11688-1:2009
0 IS0
ISO/TR 11688=1:1995(E)
Introduction
This International Technical Report provides a guideline for the
design of low-noise machinery. Most of the existing International
Technical Reports prepared in ISO/TC 43/SC I specify methods for the
measurement and/or evaluation of noise. The final objective of this
International Technical Report, however, will be noise control in
existing machinery and noise control at the design stage.
It is important that non-acoustic engineers are engaged in noise
control practice. It is of great importance for these engineers to have a
basic knowledge of noise generation and propagation characteristics
and to understand the basic principles of noise control measures.
Hence, this International Technical Report also serves as an
introduction into acoustical terms, and as a basis to the acquisition of
further knowledge in noise control.
It is strongly required to support the dissemination of the design rules
given here through standardisation.
Such considerations have led to the preparation of nternational
Technical Reports in the area of noise control.
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kSIST FprEN ISO 11688-1:2009
‘TECHNICAL REPORT @ IS0 ISO/TR 11688=1:1995(E1)
Acoustics - Recommended practice for the design of
low-noise machinery and equipment -
Part 1:
Planning
1 Scope
This International Technical Report is an aid to understanding the basic concepts of noise control in
machinery and equipment.
The recommended practice presented here is intended to assist the designer at any design stage to control
the noise of the final product. Methodical development of products was chosen as a basis for the structure
of this document (see Clause 4).
The list of design rules given in this International Technical Report is not exhaustive. Other technical
measures for reducing noise at the design stage may be used if their efficacy is identical or higher.
To solve problems going beyond the scope of this International Technical Report, the designer can refer to
the bibliography in Annex D, which presents the general state of acoustic handbooks at the time of
publication. Furthermore, reference is made to the numerous technical publications dealing with acoustical
problems.
2 References
IS0 3744:1994, Acoustics - Determination of sound power levels of noise sources using sound pressure -
Engineering method in an essentially free field over a reflecting plane.
IS0 3746:- ‘1, Acoustics - Determination of sound power levels of noise sources - Survey method
employing an enveloping measurement surface over a reflecting plane.
IS0 4871:- ‘), Acoustics - Declaration and verification of noise emission values of machinery and
equipment.
IS0 961 l:- ‘1, Acoustics - Characterization of sources of structure-borne sound with respect to the airborne
sound radiation of connected structures - Measurement of velocity at the contact points of machinery
when resiliently mounted.
IS0 9614-l : 1994, Acoustics - Determination of sound power levels of noise sources using sound intensity
- Part I: Measurement at discrete points.
IS0 9614-Z:-? Acoustics - Determination of sound power levels of noise sources using sound intensity -
Part 2: Measurement by scanning.
1) To be published.
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kSIST FprEN ISO 11688-1:2009
ISO/TR 11688=1:1995(E) 0 IS0
IS0 11200:-'1, Acoustics - Noise emitted by machinery and equipment - Guidelines for the use of basic
standards for the determination of emission sound pressure levels at the work station and at other specified
positions.
IS0 11689:-l), Acoustics - Systematic collection and comparison of noise-emission data for machinery
and equipment.
3 Definitions
For the purpose of this International Technical Report the following definitions apply:
3.7 Airborne, liquid-borne and structure-borne noise: Sound propagating through air, a liquid or a solid
structure, respectively.
3.2 Active noise components: Components of machinery, which generate noise. In many cases these
are the power converting devices generating mechanical work from power resources, such as
electrical, mechanical or magnetic energy, hydraulic pressure, internal forces, or friction. Other
noise “components” may be regions with non-steady flow and contact surfaces between moving
parts.
3.3 Psssive noise components: Components which transmit noise generated by the active components;
they do not contain noise sources but can be dominating radiators of noise. Typical passive
components are structural parts and covering panels of machinery.
3.4 Periodic noise: A noise event which is periodically repeated. Typical sources of periodic noise are
gear wheels and piston machines. It is characteristic for periodic noise that it exhibits a line
spectrum.
3.5 Tonal noise: Noise which is dominated by one or several clearly distinguishable tone(s).
3.6 Broad band noise: Noise generated by either single shocks, i.e. short duration pressure pulses or
impacts, or by turbulence in an air or fluid flow. The characteristics of broad band noise are that the
frequency analysis shows a continuous spectrum over a large frequency range.
3.7 force excitation: The excitation force is independent of the properties of the excited structure; an
example of this is the effect of a light and flexible source on a relatively stiff and heavy structure.
38 . velocity excitation: The excitation velocity is independent of the properties of the excited structure;
an example of this is a light and flexible structure excited by a relatively massive source.
Quasi-static response: .
3.9 Response of the machine at frequencies below the lowest resonant
frequency.
3.70 Resonant response: Response in a frequency range of distinct resonances.
3.77 Multi-resonant response: Response in a frequency range with many resonances.
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kSIST FprEN ISO 11688-1:2009
0 IS0
ISO/TR 11688-1:1995(E)
Design process Noise control
Y
:::
:c
Requirements concerning
5
x
:::
:::
1. Clarification of task .:.
noise behaviour from
:::
X
.:.
:::
::
-
standards, authorities .:.
X
:;:
- clarifying standards,
:.:
:i:
requirements, state of
4
- regulations of clients, state of the art,
j
:::
the art. . .
:::
:::
:::
.:*
:a:
competition, sales argument
:>
:.:
- list of specifications
:::
:::
: j:
1 x
- own experience
:;:
:*:
.>
:*:
.:.
3:
:2
- search for solution
principles
Acoustical experience and knowledge
- comparison of
for comparison of different solutions
different concepts
- acoustical rules
- selection of concept
- rough formulae
1
- diagnosis information
1 /
- experience and examples
- choice of dimensions, - literature, drawings
material . . .
- acoustical modelling and FEM
- comparison (calculation
and modelling) - acoustic devices
t
/ -stk;tion y detailed - source strengths of partial sources
(airborne, structure-borne, liquid-borne)
. . .
4. Prototyping
- measurements on
prototype
Noise measurement and
noise reduction using the prototype
- evaluation of noise
- analysis and modification
behaviour
- comparison with - acoustical diagnosis
references
L -final testing
-1
- comparison with the requirements
Clearance for series
I
Fig. 1: Stages of the design procedure; support of design process by noise
control methods
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kSIST FprEN ISO 11688-1:2009
0 IS0
ISO/TR 11688-1:1995(E)
4 Methodical design and acoustic aspects
Methodical design is an operational approach which makes use of information from a variety of disciplines,
for example machine acoustics. This way a basis is set for achieving targets and making decisions in design
and development.
The design procedure can be divided into four phases (listed below) which are increasingly specific (see
Fig. I). Increase of information from phase to phase makes it possible to sort alternative solutions with
respect to specific design criteria such as low noise level. The phases of systematic design are:
1.
Clarification of task: Make a list of requirements which is the controlling document for the whole
design task. Include noise specifications in this list with reference to legislation, the state of the art,
competitors’ products, client demand or the weighting of machine noise as a company sales
argument. (See Annex B.)
2. Conceptional design: This phase of the design process concentrates mainly on achieving the
desired objectives. Little information is available about the final product at this stage and the noise
behaviour is often assessed by comparison to known designs.
3 . Design and detail: As the design and choice of individual components progress, quantitative
estimates of noise behaviour can be made through the selection of design options.
4. Prototyping: Measurements on the prototype allow quantification of major noise sources and sound
paths. This may indicate specific measures leading to design changes. Compliance with the
requirements can be confirmed by measurements.
The following procedure can be applied in each of the four phases described above. It is very important to
follow the methodology of eliminating the most dominant noise problems in the earliest possible stage of
design:
The first step of the process is determining the major sources of noise in the machine and
establishing a priority list or scheme (see 5.2).
Once the major sources are recognised, a more detailed analysis of the noise mechanisms
must be carried out (see 5.3).
The next step is analysing and describing the direct radiation of noise from the sources to
the receiving position(s), and the transmission through the structure to the radiating
surfaces (see 5.4).
The final step
is to analyse the radi ation from those surfaces and to determine the various
contributions
to the sound pressure level at the receiving position(s).
Evaluate which combination of noise control measures is optimal.
In designing low-noise machinery one should try to identify the basic acoustic mechanisms involved by
consideration of the causal chain (Fig. 2).
All design processes have a recursive element. So at every phase a decision has to be made as to whether
the next phase can be entered or whether previous steps shall be repeated.
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kSIST FprEN ISO 11688-1:2009
0 IS0 ISO/TR 11688=1:1995(E)
I
I I
1 Part of machinery 1
Acoustical mechanism
1 Source 1
Generation
r- I
1 Path I
1 Transyission 1
1 Surface 1
Radiation
I I
Fig. 2: Causal chain of noise generation
An illustration of how the different noise mechanisms are connected is shown in Fig. 3. The first priority in
noise control is to identify the source. Different types of sources are shown in the first and second ring with
key words corresponding to the headlines of the following clauses.
Once the source type is determined, transmission through the particular medium will take place as seen in
the third ring. Finally the noise will radiate into free air or excite a structure. The figure can be used to show
that every sound source has its own characteristics, its specific transmission path through the structure and
excitation of the radiating surfaces. To control the noise from a machine with many different types of
sources, it is necessary to analyse each noise source, transmission path and radiating surface on its own to
be able to evaluate the relative importance. The next clause shows an example of such a machine.
5 Conceptual and detailed design
51 . General
Since a design solution always comprises the choice of a physical operating principle and the choice of a
functional system, it is possible to make the following general comments for the choice of design concepts.
With a high degree of probability, the mode of operation with the lowest speed and
acceleration will provide the best acoustic solution.
For a given operational principle the noise from a machine can be reduced by altering the
mass, stiffness and damping of the structure. Design parameters such as material, shape,
position, number of elements, dimensions, structure and type of connections can have a
large effect on the noise emission. If applied in the proper way such alterations may reduce
the vibration and/or radiation of the machine.
Steady flow of gases and liquids is quieter than unsteady flow.
Both in the conceptual phase and in the detailed design, the procedure described in Clause 4 and
elaborated further in the following clauses can be used for diagnosis and noise control measures. In the
conceptual phase only rough estimates, common design rules or a comparison with existing solutions is
possible. In the detailed design phase the results of detailed calculations, modelling and survey
experiments can be applied.
5
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kSIST FprEN ISO 11688-1:2009
ISO/TR 11688=1:1995(E)
0 IS0
-%$.A -u!!Ak~v
/Ii+
Fig 3: Basic model of noise generation in machines
---------------------- Page: 18 ----------------------
kSIST FprEN ISO 11688-1:2009
ISO/TR 116884:1995(E)
0 IS0
52 . Basic steps
5.2.1 Acoustical modelling and ranking
The noise behaviour in machinery with different noise sources can be visualised by an acoustic model of
the machine (see Fig. 2). To elaborate this model, the designer must first divide the machine into active and
passive noise components.
The active and passive noise components may have the capability of generating, transmitting and radiating
airborne, liquid-borne and structure-borne noise. Therefore it is necessary to analyse the noise components
for these three types of noise. The purpose of subdividing the noise components is the identification of the
dominating noise sources, transmission paths and radiating surfaces.
Then the designer must analyse along which paths noise can be propagated. Structure-borne, liquid-borne
and airborne sound paths shall be considered. Furthermore, possible direct radiation of airborne sound
from the individual active components must be considered.
Finally the sound radiating surfaces of the machine must be identified.
When the most important noise sources with their transmission paths are identified, an analysis of the
process parameters must be carried out. The dominant noise contributions have to be controlled first. It is
recommended to control the sources first before dealing with transmission paths and the radiating
surfaces.
Severe noise problems can be caused by the coincidence of driving frequencies and resonances in the
active and passive components.
General design rules:
Divide machine into active and passive noise components;
Locate airborne, liquid-borne and structure-borne noise sources;
Locate the airborne, liquid-borne and structure-borne sound paths;
Locate the sound radiating surfaces;
Identify the strongest contributions (sources, transmission paths, radiating surfaces).
5.2.2 Example
of this example is to demonstrate how acoustic modelling and noise source ranking can be
The purpose
carried out.
Fig. 4 shows a hydrostatic power pack having active noise components such as: electric motor, hydraulic
pump and a valve.
They are all connected to the reservoir in a closed circuit.
7
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kSIST FprEN ISO 11688-1:2009
0 IS0
ISO/TR 11688=1:1995(E)
1) Relief valve
2) Outlet tube (12 mm)
3) Reduction fitting (25 mm - 12 mm)
4) Pump
5) Vibration-isolated flange
6) Mounting flange
7) Cover
8) Vibration-isolated coupling
9) Electric motor
10) Reservoir
Fig. 4: Hydrostatic power pack
The power pack has active noise sources representing airborne, structure-borne and liquid-borne noise
sources.
To visualise the transmission of noise from the different noise sources in the machine a block diagram,
Fig. 5, is drawn which in graphical form illustrates the noise mechanisms of the power pack.
A list of the noise sources, paths and surfaces is shown in Tables 1 to 3
---------------------- Page: 20 ----------------------
kSIST FprEN ISO 11688-1:2009
ISO/TR 11688-1:1995(E)
0 IS0
Passive
Active Noise
Noise
Components
Components
Reservoir,
tubes and
0
machine
structure
.
.
Key
Airborne noise
lo
‘/ “& Liquid - borne noise
@
Structure-borne noise
Fig. 5: Acoustical model of power pack
9
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kSIST FprEN ISO 11688-1:2009
ISO/TR 11688-1:1995(E) 0 IS0
Table 1: Hydrostatic power pack; noise sources
I
I A Airborne noise + Major contributor
Key
S Structure-borne noise - Minor contributor
L Liquid-borne noise
II Component Component Source Source A S L
Electric Electric motor motor Magnetic Magnetic field field
Fan Fan -I- -I-
Unbalance Unbalance
Hydraulic Hydraulic pump pump Pumping Pumping + + + +
Unbalance Unbalance
Relief Relief valve valve
Flow Flow restriction restriction
Valve Valve instabilitv instability
Table 2: Hydrostatic power pack; transmission paths
I
I A Airborne noise + Major contributor
Key
S Structure-borne noise - Minor contributor
L Liquid-borne noise
Path
Component A S
Electric motor
Mounting points +
Shaft
Hydraulic pump Mounting points +
Shaft
Fluid connections
Relief valve
Mounting points
.
Fluid connections
Coupling Coupling elements
+
Tubes Steel tubes
Fluid
Reservoir Mounting points +
Plates
Fluid
Table 3: Hydrostatic power pack; radiating surfaces
I
I A Airborne noise + Major contributor
Key
S
Structure-borne noise - Minor contributor
L Liquid-borne noise
1 Component
Radiating surface A S L
Electric motor
Housing +
Hydraulic pump Housing
Tubes Walls
Reservoir
Walls +
IO
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kSIST FprEN ISO 11688-1:2009
ISO/TR 11688-1:1995(E)
0 IS0
A number of experiments were carried out on the power pack to identify the different sources, paths and
radiating surfaces concerning noise emission. The main results are shown in Table 4 as sound power
measurements in a reverberant room. All experiments were done under the same operating conditions.
Table 4: Hvdrostatic Dower Dack: effect of noise control measures
I
L
Power ‘pack noise control
WA
1500 rpm; 180 bar in dB
90
All transmission paths are present as in Fig
...
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