EN ISO 11957:2009

Acoustics - Determination of sound insulation performance of cabins - Laboratory and in situ measurements (ISO 11957:1996)

Describes a laboratory method and in situ methods for the determination of the sound insulation performance of sound-protecting cabins. Applicable to sound-protecting cabins with a leak ratio smaller than 2 %.

Akustik - Messung der Schalldämmung von Schallschutzkabinen - Messungen im Labor und im Einsatzfall (ISO 11957:1996)

Diese Internationale Norm legt Verfahren zur Messung der Schalldämmung von Schallschutzkabinen im Labor (Abschnitt 6) und im Einsatzfall (Abschnitt 7) fest. Die Schalldämmung ist die von der Kabine bewirkte Minderung des Schalldruck- oder Schalleistungspegels. Die Verfahren sind auf Schallschutzkabinen mit geringem Öffnungsanteil (  2 %) anwendbar.
Diese Internationale Norm gilt nur für eine vollständige Schallschutzkabine und nicht für die einzelnen Bauteile, aus denen sie hergestellt wurde.
ANMERKUNG 1   Die Schalldämmungen für Kabinenteile, wie z. B. Wandelemente, Türen, Fenster, Schalldämpfer, sollten nach anderen diesbezüglichen Normen gemessen werden.
Die Anforderungen an die Messumgebung im Labor basieren auf denjenigen, die in ISO 3741 festgelegt sind.

Acoustique - Détermination des performances d'isolation acoustique des cabines - Mesurages en laboratoire et in situ (ISO 11957:1996)

La présente Norme internationale décrit une méthode de laboratoire (article 6) et des méthodes in situ (article 7) pour la détermination des performances d'isolation acoustique des cabines de protection phonique. La performance d'isolation acoustique est la réduction du niveau de pression acoustique ou du niveau de puissance acoustique occasionné par la cabine. Les méthodes sont applicables à des cabines à faible taux de fuite (θ < 2 %). La présente Norme internationale s'applique exclusivement à une cabine complète et non aux composants individuels qui la constituent.  
NOTE 1 L'isolement acoustique des composants de la cabine, tels que les éléments de cloison, les portes, les fenêtres, les silencieux, etc., devrait être mesuré suivant les normes adéquates. Les exigences concernant l'environnement d'essai en laboratoire sont basées sur celles figurant dans l'ISO 3741.

Akustika - Ugotavljanje zvočnoizolacijskih lastnosti kabin - Merjenje v laboratoriju in na terenu (ISO 11957:1996)

General Information

• Status: Published
• Publication Date: 18-Aug-2009
• Withdrawal Date: 27-Feb-2010
• ICS: 17.140 - Acoustics and acoustic measurements
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 17.140.99 - Other standards related to acoustics
• Technical Committee: CEN/TC 211 - Acuostics
• Drafting Committee: CEN/TC 211 - Acuostics
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 19-Aug-2009
• Due Date: 25-Sep-2010
• Completion Date: 19-Aug-2009
• Directive: 2006/42/EC - Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast)
• Directive: 89/392/EEC - Machinery - Safety of machinery: general essential health and safety requirements
• Directive: 98/37/EC - Machinery
• Mandate: M/BC/CEN/88/13 - Standardization request to CEN/CENELEC relating to machinery
• Ref Project: SIST EN ISO 11957:2009 - Acoustics - Determination of sound insulation performance of cabins - Laboratory and in situ measurements (ISO 11957:1996)

Relations

• Replaces: EN ISO 11957:1996 - Acoustics - Determination of sound insulation performance of cabins - Laboratory and in situ measurements (ISO 11957:1996)
• Effective Date: 24-Dec-2008

Overview

EN ISO 11957:2009 (identical to ISO 11957:1996) is a CEN-adopted acoustics standard that specifies methods for the determination of sound insulation performance of sound‑protecting cabins. It defines both laboratory and in situ measurement procedures for complete cabins (not individual components) and applies specifically to cabins with a leak ratio ≤ 2%. The standard produces measurable the results such as sound pressure insulation (Dp), apparent sound pressure insulation (Dpa), A‑weighted values, and weighted single‑number ratings used to characterise cabin acoustic performance.

Key topics and requirements

• Scope and definitions: Terms such as cabin, sound pressure level (Lp), internal noise level (Lp,A), leak ratio and reverberant sound field are defined to ensure consistent measurement and reporting.
• Test environment selection: Laboratory conditions follow guidance related to reverberation rooms; in situ tests address realistic external sound fields.
• Instrumentation and calibration: Use of sound level meters, calibrators and octave/third‑octave filters in accordance with referenced IEC/ISO instrument standards is required.
• Laboratory measurements (Clause 6):
  • Cabin mounting, location and boundary conditions specified.
  • Measurement of sound pressure levels outside (reverberant room) and inside the cabin to compute Dp.
• In situ measurements (Clause 7):
  • Microphone placement inside and outside cabin, handling of non‑diffuse fields and computation of apparent insulation (Dpa).
• Derived metrics:
  • Apparent A‑weighted insulation (Dpa,A) and weighted single‑number insulation (Dpw) for simplified comparison and rating (per ISO 717‑1 method).
  • Estimated cabin noise insulation for a specified noise spectrum (Annex A).
• Uncertainty and reporting:
  • Clause on measurement uncertainty and detailed information to record and report (test object, conditions, instrumentation, acoustical data).
• Regulatory linkage:
  • Informative annexes (ZA, ZB) explain relationships with EU Directives (e.g., machinery directives) for conformity assessment.

Applications and who uses it

• Acoustic engineers and test laboratories performing certified sound insulation tests on operator booths, machine enclosures, control cabins, recording booths and similar sound‑protecting cabins.
• Manufacturers verifying product noise attenuation performance during development or for conformity claims.
• Compliance officers and certification bodies assessing conformity with EU directives and national standards.
• Facility designers specifying cabins for industrial, transportation or broadcast applications where internal noise control is critical.

Related standards

• ISO 11957 (ISO original text, 1996)
• ISO 11546‑1 / ISO 11546‑2 (noise attenuation of enclosures)
• ISO 3741 (reverberation room sound power methods)
• ISO 717‑1 (rating of airborne sound insulation)
• Relevant IEC/ISO instrument standards (sound level meters, filters, calibrators)

Keywords: EN ISO 11957:2009, sound insulation, acoustics, cabins, laboratory measurements, in situ measurements, leak ratio, sound pressure level, A‑weighted insulation.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2009
1DGRPHãþD
SIST EN ISO 11957:1999
$NXVWLND8JRWDYOMDQMH]YRþQRL]RODFLMVNLKODVWQRVWLNDELQ0HUMHQMHYODERUDWRULMX
LQQDWHUHQX,62
Acoustics - Determination of sound insulation performance of cabins - Laboratory and in
situ measurements (ISO 11957:1996)
Akustik - Messung der Schalldämmung von Schallschutzkabinen - Messungen im Labor
und im Einsatzfall (ISO 11957:1996)
Acoustique - Détermination des performances d'isolation acoustique des cabines -
Mesurages en laboratoire et in situ (ISO 11957:1996)
Ta slovenski standard je istoveten z: EN ISO 11957:2009
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 11957
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2009
ICS 17.140.01 Supersedes EN ISO 11957:1996
English Version
Acoustics - Determination of sound insulation performance of
cabins - Laboratory and in situ measurements (ISO 11957:1996)
Acoustique - Détermination des performances d'isolation Akustik - Messung der Schalldämmung von
acoustique des cabines - Mesurages en laboratoire et in Schallschutzkabinen - Messungen im Labor und im
situ (ISO 11957:1996) Einsatzfall (ISO 11957:1996)
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 European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11957:2009: E
worldwide for CEN national Members.

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

Foreword
The text of ISO 11957:1996 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 11957:2009 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 11957:1996.
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 11957:1996 has been approved by CEN as a EN ISO 11957:2009 without any modification.
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.
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.
INTERNATIONAL
IS0
STANDARD
First edition
1996-l 2-01
Acoustics - Determination of sound
insulation performance of cabins -
Laboratory and in situ measurements
Acoustique - Dgtermina tion des performances d ’isola tion acoustique des
cabines - Mesurages en laboratoire et in situ
Reference number
IS0 11957: 1996(E)
IS0 11957: 1996(E)
Contents Paae
1 Scope . 1
2 Normative references . 1
3 Definitions . 1
4 Test environment and choice of suitable quantity . 2
..............................................................................
5 Instrumentation 3
6 Measurement of sound insulation performance in the laboratory . . 3
6.1 General . 3
6.2 Cabin location . 3
6.3 Cabin mounting and conditions . 3
6.4 Measurement of the sound pressure level in the room. . 4
6.5 Measurement of the sound pressure level inside the cabin
6.6 Sound pressure insulation, Dp . 4
6.7 Measurement of noise inside the cabin due to noise
sources forming an integral part of the cabin (internal
noise level, L& .
7 Measurement of sound insulation performance in situ. .
7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2
External sound field ,.
7.3 Cabin mounting and conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
74 . Microphone positions in the room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7s . Microphone positions inside the cabin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.6 Apparent sound pressure insulation, D>
77 .
Measurement of noise inside the cabin due to noise
sources forming an integral part of the cabin (internal
noise level, &A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0 IS0 1996
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
@ IS0 IS0 11957: 1996(E)
8 Weighted sound pressure insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9 Estimated cabin noise insulation for a specific noise spectrum. 7
10 Uncertainty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11 Information to be recorded
11 .I Test object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.2 Test conditions . . . . . . . . . . . . . . .~. 8
11.3 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.4 Acoustical data . . . .*. 8
11.5 Further information . . . . . . . . . . . . . . . . . . . . . . . . .*. 8
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
12 Information to be reported
Annexes
A Estimated cabin noise insulation for a specific noise spectrum.
B Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
. . .
III
IS0 11957: 1996(E) @ IS0
Foreword
IS0 (the International Organization for Standardization) is a worldwide fed-
eration 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, governmental and non-
governmental, in lialison with ISO, also take part in the work. IS0 collabo-
rates closely with the International Electrotechnical Commission (IEC) on
all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are cir-
culated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 11957 was prepared by Technical Committee
ISO/lC 43, Acoustics, Subcommittee SC 1, Noise, on request from
CEN/TC 211, Acoustics.
Related standards concern noise attenuation measurements of enclosures
under laboratory conditions (IS0 11546-l) and in situ (IS0 11546-2).
Annexes A and B of this International Standard are for information only.
iv
INTERNATIONAL STANDARD @ IS0
IS0 11957:1996(E)
Acoustics - Determination of sound insulation performance of
cabins - Laboratory and in situ measurements
IS0 717-I :-
’ ), Acoustics - Rating of sound insu-
1 Scope
lation in buildings and of building elements - Part I:
This International Standard specifies a laboratory Airborne sound insulation.
method (clause 6) and in situ methods (clause 7) for
IS0 3741: -*), Acoustics - Determination of sound
the determination of the sound insulation performance
power levels of noise sources using sound press-
of sound-protecting cabins. The sound insulation per-
ure - Precision methods for reverberation rooms.
formance is the reduction in sound pressure level or
sound power level afforded by the cabin. The methods
IS0 4871 :I 996, Acoustics - Declaration and verifi-
are applicable to cabins with a small leak ratio
cation of noise emission values of machinery and
(e s 2 %).
equipment.
This International Standard is applicable to a complete
IEC 651 :I 979, Sound /eve/ meters.
cabin only and not to the individual components from
which it is made.
I EC 804: 1985, Integrating-averaging sound level
meters.
NOTE 1 Sound insulations for cabin components such as
wall elements, doors, windows, silencers, etc. should be
I EC 942: 1988, Sound calibrators.
measured according to other relevant standards.
I EC 1260: 1995, E lectroacoustics - Octave-band and
Requirements for the test environment in the labora-
fractional-octave-band filters.
tory are based on those given in IS0 3741.
2 Normative references
3 Definitions
The following standards contain provisions which,
For the purposes of this International Standard, the
through reference in this text, constitute provisions of
following definitions apply.
this International Standard. At the time of publication,
the editions indicated were valid. All standards are
subject to revision, and parties to agreements based
3.1 A-weighting: Frequency weighting in accord-
on this International Standard are encouraged to in-
ance with IEC 651.
vestigate the possibility of applying the most recent
editions of the standards indicated below. Members of
IEC and IS0 maintain registers of currently valid lnter- 3.2 cabin: An enclosure specially designed to shield
national Standards. human beings from environmental noise.
1) To be published. (Revision of IS0 717-I : 1982)
2) To be published. (Revision of IS0 3741: 1988 and IS0 3742:1988)
IS0 11957: 1996(E) @ IS0
3.3 sound pressure level, Lp: Ten times the log- sound pressure insulation, D>. (See note 2 and
arithm to the base 10 of the ratio of the mean-square clause 8.)
sound pressure to the square of the reference sound
pressure (= 20 PPa). It is expressed in decibels.
3.10 estimated cabin noise insulation, DpA g
Calculated reduction in A-weighted sound pressu ’re
level for a specific spectrum (the actual noise), ob-
34 . average sound pressure level (on a mean-
tained from Dp measured in accordance with this
square basis), L, :
International Standard. It is expressed in decibels.
(See annex A.)
1 oQ1 LPI+ l()W LP2+ ,. + 1p LPn
3.11 apparent estimated cabin noise insulation,
Lp =lOlg dB
n
Calculated reduction in A-weighted sound
D>A &
pressure level for a specific spectrum (the actual
noise), obtained from D> measured in accordance
with this International Standard. It is expressed in
are the sound pressure levels,
‘--Y Lp
decibels. (See note 2 and annex A.)
in decibels, to be averaged;
n is the number of values to be
3.12 internal noise level, Lp~: A-weighted average
averaged.
sound pressure level inside the cabin caused by
sound sources which are an integrated part of the
It is expressed in decibels.
cabin. It is expressed in decibels.
3.5 sound pressure insulation, Dp: Difference, in
3.13 background noise level: Averaged sound
one-third-octave or octave bands, between the sound
pressure level inside or outside the cabin when the
pressure level of an external reverberant sound field
loudspeakers, the actual environmental noise and
and the sound pressure level inside a cabin located in
the sound sources which are an integrated part of the
this field. It is expressed in decibels.
cabin are switched off. It is expressed in decibels.
3.6 apparent sound pressure insulation, D$ Dif-
3.14 leak ratio, 8: Ratio between the area of all
ference, in one-third-octave or octave bands, between
openings of the cabin and the total interior surface
the sound pressure level in a room and the sound
area (including openings) of the cabin.
pressure level in a cabin located in the room. It is ex-
NOTES
pressed in decibels. The sound field in the room need
not necessarily be diffuse.
3 The reciprocal value of the leak ratio is designated the
seal ratio, w(w= l/e>.
NOTE 2 The word “apparent” indicates that the measure-
ment has been carried out under in situ conditions.
4 Openings provid ed with sufficiently effecti silencers
opening
are not regarded as s in this context.
3.7 apparent A-weighted sound pressure insu-
lation, DlpA: Difference in A-weighted sound pressure
3.15 empty cabin: Normally equipped cabin with no
levels measured in the room and in the cabin, respec-
human beings inside.
tively, when the actual environmental noise is used as
the sound source. It is expressed in decibels. (See
3.16 reverberant sound field: That portion of the
note 2.)
sound field in the test room where the influence of
sound received directly from the source is negligible.
3.8 weighted sound pressure insulation, Dpw:
Single-number value determined in accordance with
3.17 room: Enclosed space, external to the cabin,
the method stated in IS0 717-1. It is expressed in
where sound is generated.
decibels. However, the sound reduction index used in
IS0 717-1 is replaced by the sound pressure insula-
tion, Dp. (See clause 8.)
4 Test environment and choice
of suitable quantity
3.9 apparent weighted sound pressure insula-
tion, D&,: Single-number value determined in ac-
If the test is conducted in a laboratory (clause 6), the
cordance’ with the method stated in IS0 717-1. It is
test environment shall be a reverberation room as
expressed in decibels. However, the sound reduction
specified in IS0 3741. If the test is conducted in situ
index used in IS0 717-1 is replaced by the apparent
@ IS0
IS0 11957:1996(E)
8 For measurements carried out in situ, class 2 instru-
(clause 7), no specific requirements concerning the
ments are acceptable.
room need be fulfilled. An external sound field gener-
ated in the room is used to determine the cabin sound
pressure insulation.
Differences can occur between laboratory and in situ
6 Measurement of sound insulation
test results. Therefore, only data based on the same
performance in the laboratory
measurement method shall be used when comparing
the performance of different cabins.
6.1 General
NOTE 5 The size and volume of the cabin may influence
the sound insulation performance. Consequently, it is rec- The test environment shall be a reverberation room
ommended that only data for cabins of approximately equal complying with the specifications given in IS0 3741.
sizes be used when comparing the performance of different
cabins.
A reverberant sound field is generated in the room and
the sound pressure level difference between the room
In cases where a single-number value is wanted as a
and the inside of an empty cabin is determined. (See
general quantity describing the sound insulation, the
6.4 to 6.6.)
weighted sound pressure insulation, D!, w, is the pre-
ferred quantity. The weighted sound tiressure insu-
lation is a practical single-number value to be used for
6.2 Cabin locations
a rough comparison of different cabins. However, this
quantity shall not be taken as a general measure of
The cabin shall be placed asymmetrically on the floor
the sound insulation performance of the cabin, as the
in such a way that no cabin wall is parallel to any wall
performance in actual situations strongly depends on
of the room.
the spectrum of the actual noise.
For measurements in the frequency range from
It is possible to calculate approximately the reduction
100 Hz to 10 000 Hz, the distance between the cabin
in the A-weighted sound pressure level due to the
and the walls and ceiling of the room shall be at least
cabin, using a known spectrum of the environmental
one-half wavelength corresponding to the centre fre-
noise (the actual noise). (See annex A.)
quency of the lowest frequency band of interest.
Furthermore, the distance between the cabin and any
diffusing elements in the room shall be at least one-
half of this wavelength. For measurements in the fre-
quency range from 50 Hz to 80 Hz, the distance shall
5 Instrumentation
be at least 2 m.
The cabin shall be present during all measurements in
The instrumentation system, including microphone and
cable, shall meet the requirements for a type 1 instru- the room.
ment as specified in IEC 651 or, in the case of integrat-
ing-averaging sound level meters, the requirements
for a type 1 instrument as specified in IEC 804.
6.3 Cabin mounting and conditions
NOTE 6 Generally, an integrating-averaging sound level
The cabin shall be installed as specified by the manu-
meter is preferred.
facturer.
For measurements in octave or one-third-octave
The cabin shall be empty during the measurements.
bands, the instrumentation system shall meet the re-
Unless otherwise specified in the operating instruc-
quirements for a class 1 filter as specified in IEC 1260.
tions for the cabin, the doors and windows shall be
closed, noise sources forming an integral part of the
Before and after each series of measurements, the
cabin such as ventilating fans shall be switched off,
stability and calibration of the entire instrumentation
and valves or dampers in the ventilation system shall
shall be verified at one or more frequencies over the
be open when measuring the sound insulation per-
frequency range of interest using an acoustical calibra-
form
...