EN ISO 2151:2004

SLOVENSKI STANDARD
01-september-2004
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Acoustics - Noise test code for compressors and vacuum pumps Engineering method
(grade 2) (ISO 2151:2004)
Kompressoren und Vakuumpumpen - Bestimmung der Geräuschemission - Verfahren
der Genauigkeitsklasse 2 (ISO 2151:2004)
Acoustique - Code d'essai acoustique pour les compresseurs et les pompes a vide -
Méthode d'expertise (classe de précision 2) (ISO 2151:2004)
Ta slovenski standard je istoveten z: EN ISO 2151:2004
ICS:
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
23.140 .RPSUHVRUMLLQSQHYPDWLþQL Compressors and pneumatic
VWURML machines
23.160 Vakumska tehnologija Vacuum technology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 2151
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2004
ICS 17.140.20; 23.140
English version
Acoustics - Noise test code for compressors and vacuum pumps
Engineering method (grade 2) (ISO 2151:2004)
Acoustique - Code d'essai acoustique pour les Akustik - Geräuschmessnorm für Kompressoren und
compresseurs et les pompes à vide - Méthode d'expertise Vakuumpumpen - Verfahren der Genauigkeitsklasse 2
(classe de précision 2) (ISO 2151:2004) (ISO 2151:2004)
This European Standard was approved by CEN on 16 January 2004.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
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Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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EUROPÄISCHES KOMITEE FÜR NORMUNG
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© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 2151:2004: E
worldwide for CEN national Members.

CORRECTED 2004-03-17
Foreword
This document (EN ISO 2151:2004) has been prepared by Technical Committee ISO/TC 118
"Compressors, pneumatic tools and pneumatic machines" in collaboration with Technical
Committee CEN/TC 232 "Compressors - Safety", the secretariat of which is held by SIS.
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 August 2004, and conflicting national
standards shall be withdrawn at the latest by August 2004.
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 EU
Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 2151:2004 has been approved by CEN as EN ISO 2151:2004 without any
modifications.
ANNEX ZA
(informative)
Relationship between this European Standard and the Essential
Requirements of EU Directive 98/37 EEC
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 EEC.
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 given in Table ZA.1 confers, within the
limits of the scope of this standard, a presumption of conformity with the corresponding Essential
Requirements of that Directive and associated EFTA regulations.
WARNING: Other requirements and other EU Directives may be applicable to the product(s)
falling within the scope of this standard.
INTERNATIONAL ISO
STANDARD 2151
Second edition
2004-02-01
Acoustics — Noise test code for
compressors and vacuum pumps —
Engineering method (Grade 2)
Acoustique — Code d'essai acoustique pour les compresseurs et les
pompes à vide — Méthode d'expertise (classe de précision 2)

Reference number
ISO 2151:2004(E)
©
ISO 2004
ISO 2151:2004(E)
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ii © ISO 2004 – All rights reserved

ISO 2151:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 2
3 Terms and definitions. 2
4 Sound power level determination . 5
4.1 General. 5
4.2 Uncertainty. 6
4.3 Test arrangement. 6
5 Emission sound pressure level determination at the work station . 7
5.1 Work station. 7
5.2 Determination of L from L . 8
pWSA WA
5.3 Method for determination of L when L is not to be determined . 9
pWSA WA
6 Mounting, loading and operating conditions of compressor or vacuum pump during
noise tests. 9
6.1 General. 9
6.2 Mounting. 9
6.3 Loading and operating conditions . 9
7 Test report. 10
8 Declaration and verification of noise emission values . 10
Annex A (informative) Example test reports. 11
Annex B (informative) Model form for declared noise emission values. 17
Annex C (normative) Parallelepiped measurement surface . 18
Annex D (normative) Hemispherical measurement surface . 20
Annex E (informative) Examples of reference box for different machines. 22
Bibliography . 25

ISO 2151:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 2151 was prepared by Technical Committee ISO/TC 118, Compressors, pneumatic tools and pneumatic
machines, Subcommittee SC 6, Air compressors.
This second edition cancels and replaces the first edition (ISO 2151:1972), which has been technically revised.
iv © ISO 2004 – All rights reserved

ISO 2151:2004(E)
Introduction
The noise test code presented by this International Standard describes methods for determining and
presenting the acoustical characteristics of compressors and vacuum pumps, i.e. the total noise level from the
compressor or vacuum pump expressed as sound power level, or the emission sound pressure level at the
work station or other specified positions.
Based on current industry practice, this noise test code requires the compressor or vacuum pump under test
to be run under conditions representing the noisiest operation in typical usage — full-load for compressors
and off-load for vacuum pumps.
It needs to be noted that operators' exposure to noise depends upon the characteristics of individual
applications and environmental factors beyond the control of the manufacturers of compressors and vacuum
pumps.
This International Standard does not give requirements for octave band analysis, however, where there is an
interest this can be undertaken.

INTERNATIONAL STANDARD ISO 2151:2004(E)

Acoustics — Noise test code for compressors and vacuum
pumps — Engineering method (Grade 2)
1 Scope
This International Standard specifies methods for the measurement, determination and declaration of the
noise emission from portable and stationary compressors and vacuum pumps. It prescribes the mounting,
loading and working conditions under which measurements are to be made, and includes measurement or
determination of the noise emission expressed as
 the sound power level under specified load conditions,
 the emission sound pressure level at the work station under specified load conditions.
It is applicable to
 compressors for various types of gases,
 oil-lubricated air compressors,
 oil-flooded air compressors,
 water injected air compressors,
 oil-free air compressors,
 compressors for handling hazardous gases (gas compressors),
 compressors for handling oxygen,
 compressors for handling acetylene,
 high-pressure compressors [over 4 Mpa (40 bar)],
 compressors for application at low inlet temperatures, i.e. below 0 °C,
 large compressors (over 1 000 kW input power),
 portable and skid-mounted air compressors, and
 rotary positive displacement blowers and centrifugal blowers and exhausters in applications u 0,2 MPa
(u 2 bar).
It is not applicable to
 compressors for gases other than acetylene having a maximum allowable working pressure of less than
0,5 bar/0,05 MPa,
 refrigerant compressors used in refrigerating systems or heat pumps,
 hand-held portable compressors.
ISO 2151:2004(E)
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 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
ISO 4871:1996, Acoustics — Declaration and verification of noise emission values of machinery and
equipment
ISO 9614-1:1993, Acoustics — Determination of sound power levels of noise sources using sound intensity —
Part 1: Measurement at discrete points
ISO 9614-2:1996, Acoustics — Determination of sound power levels of noise sources using sound intensity —
Part 2: Measurement by scanning
ISO 11201:1995, Acoustics — Noise emitted by machinery and equipment — Measurement of emission
sound pressure levels at a work station and at other specified positions — Engineering method in an
essentially free field over a reflecting plane
ISO 11202:1995, Acoustics — Noise emitted by machinery and equipment — Measurement of emission
sound pressure levels at a work station and at other specified positions — Survey method in situ
ISO 11203:1995, Acoustics — Noise emitted by machinery and equipment — Determination of emission
sound pressure levels at a work station and at other specified positions from the sound power level
IEC 61672-1:2002, Electroacoustics — Sound level meters — Specifications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
compressor
machine which compresses air, gases or vapours to a pressure higher than the inlet pressure
NOTE A compressor comprises the bare compressor itself, the prime mover and any component or device supplied
with the compressor.
3.2
vacuum pump
device for creating, improving and/or maintaining vacuum
NOTE A vacuum pump comprises the bare pump, the prime mover and any component or device supplied with the
vacuum pump.
3.3
emission
airborne sound radiated by a well-defined noise source (e.g. the machine under test) under specified
operating and mounting conditions
NOTE 1 Adapted from ISO 11203:1995.
NOTE 2 Noise emission values can be incorporated in a product label and/or published in a product specification. The
basic noise emission descriptors are the sound power level of the product itself and the emission sound pressure levels at
the work station and at other specified positions in the vicinity of the product (if any).
2 © ISO 2004 – All rights reserved

ISO 2151:2004(E)
3.4
emission sound pressure
p
sound pressure, expressed in pascals, at a specified position near a noise source, when the source is in
operation under specified operating and mounting conditions on a reflecting plane surface, corrected for
background noise and reflections from room surfaces other than the plane over which the machine under test
is placed
NOTE Adapted from ISO 11203:1995.
3.5
emission sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the emission sound pressure to the square
of the reference sound pressure, expressed in decibels, and measured with a particular time weighting and a
particular frequency weighting selected from those defined in IEC 61672-1:2002
EXAMPLE A-weighted emission sound pressure level, L .
pA
NOTE 1 The reference sound pressure is 20 µPa.
NOTE 2 L levels are established as L time-averaged sound pressure levels measured with an integrating-
pA pAeqT
averaging sound level meter meeting the requirements of IEC 61672-1:2002. L is usually abbreviated to L . For
pAeqT pA
further details of L see ISO 3744:1994, 3.2.1.
pAeqT
NOTE 3 Adapted from ISO 11203:1995.
3.6
sound power
W
rate per unit time, expressed in watts, at which airborne sound energy is radiated by a source
[ISO 3744:1994]
3.7
sound power level
L
W
ten times the logarithm to the base 10 of the ratio of the sound power radiated by the source under test to the
reference sound power, expressed in decibels
NOTE 1 The frequency weighting or the width of the frequency band must be indicated. For example, A-weighted
sound power level L .
WA
−12
NOTE 2 The reference sound power is 1 pW (1 pW = 10 W).
NOTE 3 Adapted from ISO 3744:1994.
3.8
sound intensity
product of the sound pressure at a point and the associated particle velocity
NOTE 1 It is a vectorial quantity.
NOTE 2 See ISO 9614-1 and ISO 9614-2 for further guidance on sound intensity.
ISO 2151:2004(E)
3.9
partial sound power
P
i
time-averaged rate of flow of sound energy through an element (segment) of a measurement surface, given
by
G G
P=×IS=I ×S
ii i ni i
where
I is the signed magnitude of the normal sound intensity component measured at position i on the
ni
measurement surface;
S is the area of the segment of surface associated with point i.
i
3.10
background noise correction
K
correction term to account for the influence of background noise on the surface sound pressure level,
expressed in decibels
NOTE 1 K is frequency dependent.
NOTE 2 The correction in the case of A-weighting is denoted K .
1A
NOTE 3 Adapted from ISO 3744:1994.
3.11
environmental correction
K
correction term to account for the influence of reflected or absorbed sound on the surface sound pressure
level, expressed in decibels
NOTE 1 K is frequency dependent.
NOTE 2 The correction in the case of A-weighting is denoted K .
2A
NOTE 3 Adapted from ISO 3744:1994.
3.12
reference box
hypothetical surface which is the smallest rectangular parallelepiped that just encloses the source and
terminates on the reflecting plane
[ISO 3744:1994]
3.13
measurement surface
hypothetical surface of area S, enveloping the source, on which the measurements are made
NOTE The measurement surface terminates on the reflecting plane.
3.14
measurement distance
distance, d, from the reference box to the parallelepiped measurement surface, or radius, r, of the
hemispherical measurement surface
NOTE Adapted from ISO 3744:1994.
4 © ISO 2004 – All rights reserved

ISO 2151:2004(E)
3.15
noise emission declaration
information on the noise emitted by the machine given by the manufacturer or supplier in technical documents
or other literature concerning noise emission values
3.16
uncertainty
K
value of the total uncertainty associated with a measured noise emission value and the production, expressed
in decibels
[ISO 4871:1996]
NOTE See also 4.2.
3.17
declared dual-number noise emission value
L, K
noise emission value, L, and its associated uncertainty, K, given in the noise emission declaration
NOTE 1 The symbols used are
 A-weighted sound power level, L , with uncertainty, K , and
WAd WAd
 A-weighted emission sound pressure level, L , with uncertainty, K .
pAd pAd
NOTE 2 Adapted from ISO 4871:1996.
3.18
work station
position in the vicinity of the compressor or vacuum pump under test, intended for the operator
NOTE 1 For the purposes of this International Standard, this is the surface enveloping the machine on test at a
distance of 1 m from the reference box (see 3.12).
NOTE 2 Adapted from ISO 11203:1995.
3.19
A-weighted emission sound pressure level at the work station
L
pWSA
energy average of the A-weighted emission sound pressure levels at the work station
4 Sound power level determination
4.1 General
The sound power level shall be determined according to either of the basic standards ISO 3744 or ISO 9614-1
or ISO 9614-2, yielding Grade 2 level of accuracy.
The sound power level shall be given as A-weighted sound power level in decibels referenced to 1 pW (dB re
1 pW).
NOTE 1 Octave band information may also be obtained.
Consider the following when choosing which International Standard to use.
ISO 3744 assumes a non-reverberant environment and low background noise. It specifies a method to
calculate sound power level from sound pressure levels measured on a surface enveloping the compressor or
vacuum pump.
ISO 2151:2004(E)
ISO 9614-1 or ISO 9614-2 can be used in most environments including semi-reverberant and/or when
extraneous noise sources exist. It specifies methods for determining the sound power level from sound
intensity levels measured on a surface enveloping the compressor or vacuum pump. Depending on the level
of reverberation and extraneous noise, it can provide A-weighted sound power level data with Grade 2 or 3
accuracy.
NOTE 2 Further information on sound power is given in ISO 3740.
4.2 Uncertainty
The uncertainty of the determination of the sound power level comprises the measurement uncertainty of
r
...