SIST EN ISO 15667:2001
(Main)Acoustics - Guidelines for noise control by enclosures and cabins (ISO 15667:2000)
Acoustics - Guidelines for noise control by enclosures and cabins (ISO 15667:2000)
Akustik - Leitfaden für den Schallschutz durch Kapseln und Kabinen (ISO 15667:2000)
Diese Internationale Norm befaßt sich mit der Wirksamheit von Schallschutzkapseln. Sie legt die schall- und betriebstechnischen Anforderungen fest, die zwischen dem Lieferanten oder Hersteller und dem Anwender solcher Kapseln zu vereinbaren sind. Diese Internationale Norm ist auf die beiden folgenden Arten von Schallschutzkapseln anwendbar: a) Kabinen zum Schutz von Bedienungspersonal vor der Einwirkung von Geräuschen. Für freistehende Kabinen und an Maschinen angebrachte Kabinen (z.B. Fahrzeuge, Krane) sind unterschiedliche Anforderungen zu erfüllen, etc.
Acoustique - Lignes directrices pour la réduction du bruit au moyen d'encoffrements et de cabines (ISO 15667:2000)
La présente Norme internationale traite des performances des encoffrements et des cabines destinés à la réduction du bruit. Elle précise les exigences acoustiques et d'utilisation qui doivent être convenues entre le fournisseur ou le constructeur, et l'utilisateur de ces encoffrements et cabines. La présente Norme internationale s'applique à deux types d'encoffrements; et de cabines acoustiques, comme suit.a) Les cabines pour la protection des opérateurs contre le bruit: les cabines autoporteuses et les cabines fixées à des machines (par exemple, véhicules, grues).b) Les encoffrements autoporteurs couvrant ou enveloppant des machines. Ces encoffrements dont une fraction inférieure à 10 % de leur surface totale est ouverte et non traitée du point de vue acoustique sont le principal objet de la présente Norme internationale.Dans la présente Norme internationale, l'accent est mis sur les constructions légères. Toutefois, les structures épaisses, massives, par exemple des murs en briques, ne sont pas exclues.Les encoffrements et cabines dont plus de 10 % de la surface est ouverte et non traitée appartiennent à la catégorie des encoffrements partiels. Ils ne font pas l'objet de la présente Norme internationale.Un troisième type d'encoffrement, les encoffrements; intégrés qui font partie de la machine et qui y sont solidement fixés, ne fait pas l'objet de la présente Norme internationale.
Akustika - Smernice za varovanje pred hrupom z okrovi in kabinami (ISO 15667:2000)
General Information
Related Packages
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2001
Akustika - Smernice za varovanje pred hrupom z okrovi in kabinami (ISO
15667:2000)
Acoustics - Guidelines for noise control by enclosures and cabins (ISO 15667:2000)
Akustik - Leitfaden für den Schallschutz durch Kapseln und Kabinen (ISO 15667:2000)
Acoustique - Lignes directrices pour la réduction du bruit au moyen d'encoffrements et
de cabines (ISO 15667:2000)
Ta slovenski standard je istoveten z: EN ISO 15667:2000
ICS:
17.140.99 Drugi standardi v zvezi z Other standards related to
akustiko acoustics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN ISO 15667
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2000
ICS 17.140.10
English version
Acoustics - Guidelines for noise control by enclosures and
cabins (ISO 15667:2000)
Acoustique - Lignes directrices pour la réduction du bruit au Akustik - Leitfaden für den Schallschutz durch Kapseln und
moyen d'encoffrements et de cabines (ISO 15667:2000) Kabinen (ISO 15667:2000)
This European Standard was approved by CEN on 1 May 2000.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2000 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15667:2000 E
worldwide for CEN national Members.
Page 2
Foreword
Corrected 2001-04-11
The text of the International Standard ISO 15667:2000 has been prepared by Technical
Committee ISO/TC 43 "Acoustics" in collaboration with 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 November 2000, and conflicting
national standards shall be withdrawn at the latest by November 2000.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United
Kingdom.
Endorsement notice
The text of the International Standard ISO 15667:2000 was approved by CEN as a European
Standard without any modification.
NOTE: Normative references to International Standards are listed in annex ZA (normative).
Page 3
Annex ZA (normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions
of any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications,
indicated by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 140-3 1995 Acoustics - Measurement of sound EN ISO 140-3 1995
insulation in buildings and of
building elements - Part 3:
Laboratory measurements of
airborne sound insulation of
building elements
ISO 717-1 1996 Acoustics - Rating of sound EN ISO 717-1 1996
insulation in buildings and of
building elements - Part 1: Airborne
sound insulation
ISO 11546-1 1995 Acoustics - Determination of sound EN ISO 11546-1 1995
insulation performances of
enclosures - Part 1: Measurements
under laboratory conditions (for
declaration purposes)
ISO 11546-2 1995 Acoustics - Determination of sound EN ISO 11546-2 1995
insulation performances of
enclosures - Part 2: Measurements
in situ (for acceptance and
verification purposes)
ISO 11957 1996 Acoustics - Determination of sound EN ISO 11957 1996
insulation performance of cabins -
Laboratory and in situ
measurements
ISO 14163 1998 Acoustics - Guidelines for noise EN ISO 14163 1998
control by silencers
INTERNATIONAL ISO
STANDARD 15667
First edition
2000-05-01
Acoustics — Guidelines for noise control
by enclosures and cabins
Acoustique — Lignes directrices pour la réduction du bruit au moyen
d'encoffrements et de cabines
Reference number
ISO 15667:2000(E)
©
ISO 2000
ISO 15667:2000(E)
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ii © ISO 2000 – All rights reserved
ISO 15667:2000(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 General principles and operational considerations.4
4.1 Sound source.4
4.2 Sound propagation paths .4
4.3 Efficient noise control .6
5 Types of enclosures and cabins and particular requirements .8
5.1 Enclosures.8
5.2 Cabins .13
6 Acoustic requirements, planning and verification of noise control.13
6.1 Target data.13
6.2 Planning.14
6.3 Measurements.16
7 Information on enclosures.18
7.1 Information to be provided by the user.18
7.2 Information to be provided by the manufacturer .19
Annex A (informative) Examples of construction.20
Annex B (informative) Case studies.38
Bibliography.49
ISO 15667:2000(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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 15667 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee
SC 1, Noise.
Annexes A and B of this International Standard are for information only.
iv © ISO 2000 – All rights reserved
ISO 15667:2000(E)
Introduction
Acoustic enclosures and cabins provide a reduction of airborne sound on the propagation path from the machine
(or a set of machines) to nearby work stations or to the environment. This International Standard describes criteria
which determine the acoustic performance of enclosures and cabins with consideration of operational aspects.
INTERNATIONAL STANDARD ISO 15667:2000(E)
Acoustics — Guidelines for noise control by enclosures and
cabins
1 Scope
This International Standard deals with the performance of enclosures and cabins designed for noise control. It
outlines the acoustical and operational requirements which are to be agreed upon between the supplier or
manufacturer and the user of such enclosures and cabins. This International Standard is applicable to two types of
acoustic enclosures and cabins, as follows.
a) Cabins for noise protection of operators: free-standing cabins and cabins attached to machines (e.g. vehicles,
cranes).
b) Free-standing enclosures covering or housing machines: enclosures with a fraction of acoustically untreated
open area of less than 10 % of the total surface are the main subject of this International Standard.
In this International Standard, emphasis is put on lightweight constructions. However, thick, massive structures as,
for example, brick walls, are not excluded.
Enclosures and cabins with more than 10 % open and untreated area belong to the category of partial enclosures.
They are not the subject of this International Standard.
A third type of enclosure, integrated enclosures which form a part of the machine and are firmly attached to it, is not
the subject of this International Standard.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 140-3, Acoustics — Measurement of sound insulation in buildings and of building elements — Part 3:
Laboratory measurements of airborne sound insulation of building elements.
ISO 717-1, Acoustics — Rating of sound insulation in buildings and of building elements — Part 1: Airborne sound
insulation.
ISO 3740 series, Acoustics — Determination of sound power levels of noise sources using sound pressure.
ISO 9614 (all parts), Acoustics — Determination of sound power levels of noise sources using sound intensity.
ISO 11200 series, Acoustics — Noise emitted by machinery and equipment.
ISO 11546-1:1995, Acoustics — Determination of sound insulation performance of enclosures — Part 1:
Measurements under laboratory conditions (for declaration purposes).
ISO 15667:2000(E)
ISO 11546-2:1995, Acoustics — Determination of sound insulation performance of enclosures — Part 2:
Measurements in situ (for acceptance and verification purposes).
ISO 11957:1996, Acoustics — Determination of sound insulation performance of sound protecting cabins —
Laboratory and in situ measurements.
ISO 14163, Acoustics — Guidelines for noise control by silencers.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
enclosure
structure covering or housing a sound source (machine) for protection of the environment from this sound source
(machine)
NOTE The shape may be box-like or follow the contour of machine parts. Box-shaped enclosures consist of walls and a
roof. The enclosure may have openings for doors, windows, ventilation, material flow, etc.; see Figure 4.
3.2
cabin
construction specially designed for the protection of human beings (e.g. machine operators) from environmental
noise, consisting of a fully enveloping structure
NOTE 1 Adapted from ISO 11957:1996.
NOTE 2 A floor is not always a component of the cabin.
3.3
sound power insulation of the enclosure
insertion loss of the enclosure
D
W
difference between the levels of the sound powers emitted from the sound source (machine) with and without the
enclosure, in one-third-octave bands or octave bands, measured according to ISO 11546-1 or ISO 11546-2
NOTE 1 The sound power insulation (or insertion loss) is expressed in decibels, dB.
NOTE 2 This spectrum of values is useful for general planning of environmental noise control for locations at some distance
from the source, e.g. in the reverberant field of an industrial hall or in the neighbourhood of a plant.
3.4
weighted sound power insulation of the enclosure
D
W,w
single-number value determined in accordance with the method stated in ISO 717-1, except that the sound
reduction index (or transmission loss) is replaced by the insertion loss, D
W
NOTE 1 The weighted sound power insulation is expressed in decibels, dB.
NOTE 2 The single-number value is useful for a rough comparison of different enclosures and for general acoustical planning
inside buildings without detailed knowledge of the source spectrum.
NOTE 3 Adapted from ISO 11546-2:1995.
2 © ISO 2000 – All rights reserved
ISO 15667:2000(E)
3.5
panel transmission loss
R
sound reduction index (or transmission loss) of individual panels from which the enclosure is made, in accordance
with ISO 140-3
NOTE 1 The panel transmission loss is expressed in decibels, dB.
NOTE 2 In a limited range of medium frequencies (typically 250 Hz to 1 000 Hz), the insertion loss, D ,ofacompletely
W
sealed enclosure is approximately related to the panel transmission loss, R,by
DR�� 10lg(�) dB (1)
W
where � denotes the average absorption coefficient of the internal side of the panels. While spectral information on R and � is
often provided, the relation (1) primarily gives an upper limit and is not a reliable foundation for predicting the actual insertion
loss, D . Leakages, insufficiently acoustically treated openings, and flanking transmission of structure-borne sound result in
W
smaller values of the actual insertion loss.
NOTE 3 For measurements of the airborne sound insulation of small building elements with openings, see ISO 140-10 [11].
3.6 Sound pressure insulation, D
p
3.6.1
sound pressure insulation for enclosures
D
p
difference between the levels of the sound pressures at a specified position with and without an enclosure, in one-
third-octave bands or octave bands
NOTE 1 The sound pressure insulation is expressed in decibels, dB.
NOTE 2 This spectrum of values is useful for the detailed analysis of the acoustic performance of an enclosure in different
directions.
NOTE 3 For measurements of the sound pressure insulation of an enclosure, see ISO 11546-1 and ISO 11546-2.
3.6.2
sound pressure insulation for cabins
D
p
difference between the levels of the sound pressures in an external diffuse sound field and in a cabin located in this
field, in one-third-octave bands or octave bands
NOTE 1 The sound pressure insulation is expressed in decibels, dB.
NOTE 2 For measurements of the sound pressure insulation of a cabin see ISO 11957.
NOTE 3 Adapted from ISO 11957:1996.
3.7
apparent sound pressure insulation of a cabin
D�
p
difference between the levels of the sound pressures in a room with arbitrary sound field distribution and in a cabin
located in the room, in one-third-octave bands or octave bands
NOTE 1 The apparent sound pressure insulation of a cabin is expressed in decibels, dB.
NOTE 2 The sound field in the room may not necessarily be diffuse.
NOTE 3 For measurements of the apparent sound pressure insulation of an enclosure, see ISO 11957.
NOTE 4 Adapted from ISO 11957:1996.
ISO 15667:2000(E)
3.8
A-weighted sound pressure insulation
D
pA
single-number value determined for the actual sound source spectrum, describing the reduction in the A-weighted
sound pressure level at a specified position due to the enclosure or in a cabin located in a diffuse sound field
NOTE 1 The A-weighted sound pressure insulation is expressed in decibels, dB.
NOTE 2 This single-number value is most relevant for describing the actual acoustic performance of an enclosure for a
particular machine, e.g. at a distance of 1 m from a machine enclosure or at any position inside a cabin.
3.9
estimated noise insulation due to the enclosure
D
pA,e
single-number value determined for a specific sound source spectrum, describing the reduction in the A-weighted
sound pressure level at a specified position due to the enclosure
NOTE 1 The estimated noise insulation due to the enclosure is expressed in decibels, dB.
NOTE 2 This single-number value is most relevant for estimating the acoustic performance of an enclosure without detailed
knowledge about the source spectrum.
3.10
leak ratio
�
ratio between the area of all acoustically untreated openings of the enclosure and the total interior surface area of
the enclosure (including openings)
NOTE Adapted from ISO 11546-1:1995 and ISO 11546-2:1995.
4 General principles and operational considerations
4.1 Sound source
The sound source (or sources) to be acoustically treated by an enclosure shall be clearly identified. The radiated
airborne sound shall be measured according to the relevant International Standards of the ISO 3740, ISO 9614 or
ISO 11200 series.
The provision of an enclosure will result in a build-up of internal heat. Air-moving devices and auxiliary equipment
supplied with the enclosure for removing the heat and for air-conditioning shall be considered as additional sound
sources.
4.2 Sound propagation paths
Several paths of sound propagation from a sound source in an enclosure to the environment can be grouped into
four categories as shown in Figure 1.
4 © ISO 2000 – All rights reserved
ISO 15667:2000(E)
Figure 1 — Block diagram of sound propagation paths
a) Path 1 for airborne sound through openings (or leaks) of the enclosure requires most attention. At very low
frequencies, where the dimensions of the enclosure are small when compared to the wavelength and where
there is little or no absorption by the enclosure lining, the volume of the enclosure and the constriction of the
openings form a Helmholtz resonator, which may result in a negative insertion loss of the enclosure. At high
frequencies, where the enclosure provides for substantial dissipation, the leak ratio � and the dissipation of
sound in linings close to the openings determine the transmission of sound along path 1. For acoustically
untreated openings, the high frequency sound reduction index (or transmission loss) R along path 1 is
estimated from:
R ��10lg(�) dB (2)
b) Path 2 for sound propagation through the enclosure walls is typically controlled by laboratory tests on well-
sealed enclosures without flanking transmission of structure-borne sound. At very low frequencies, the ratio of
the compliance of the air inside the enclosure and the volume compliance of the enclosure walls determines
the insertion loss of the enclosure [see equation (3)]. At low frequencies, the compliance of the air between the
machine and a nearby enclosure wall may resonate with the mass of the wall, which results in a minimum of
the insertion loss.
At intermediate and higher frequencies, the panel transmission loss is effective. It is determined by the
impedance of the impervious shell and the attenuation on the propagation path through the inside lining. Single-
wall constructions exhibit a sound reduction index (or transmission loss) which is mass controlled up to a panel
weight of about 15 kg/m and frequencies of about 2 kHz. Double-wall constructions are used to improve the
sound reduction index (or transmission loss) at intermediate frequencies above the double-wall resonance
frequency. Minima of the sound reduction index (or transmission loss) due to coincidence of the incident sound
with free bending waves on the panel are mostly avoided by sound damping by the lining at frequencies above
2 kHz. At all but very low frequencies where the perimeter of the enclosure is smaller than the wavelength of
airborne sound, the radiation efficiency of forced bending response� � 1.
F
NOTE The radiation efficiency is defined in ISO/TR 7849 [14].
c) Path 3 contains the radiation of free bending waves from the enclosure walls. Since mostly thin panels are
used for the enclosure, the radiation efficiency � of limp panels is small and predominantly determined by
ow
ISO 15667:2000(E)
their clamped edges or attachment points. Free bending waves are largely caused by flanking transmission of
structure-borne and airborne sound. Damping of the panels provides for dissipation of such waves. Free
bending waves on the enclosure frame may need to be considered at frequencies above 1 kHz.
d) Path 4 is for the radiation with efficiency � of structure-borne and airborne sound from flanking components
of
which is unaffected by the enclosure. The floor, unenclosed parts of the machine, material supplied to the
machine, and pipework connected to the machine are examples of flanking components. The contribution from
this path finally limits the acoustic performance of an otherwise well-designed enclosure.
In critical cases, the sound transmission via all the different paths needs to be considered. The individual
contributions may be determined from appropriate measurements or calculations. The distinction between
contributions from path 2 and path 3 is the most difficult. In addition, if possible, the background sound pressure
level L should be determined for the case where the sound source to be enclosed is turned off.
pb
4.3 Efficient noise control
NOTE For concerns to be addressed for efficient noise control by enclosures and cabins, see also references [1], [2], [6],
[9].
4.3.1 Select an enclosure or cabin which is matched to the particular task of housing a machine or protecting a
work station under general operating criteria, including availability of space, safety aspects, material flow, etc.
4.3.2 Generally, the acoustic performance of panels mounted on a mechanically stable frame is sufficient in
terms of absorption and sound reduction index (or transmission loss) if common materials are used. Typical
components shown in Figure 2 are
� outer shell: 1,5 mm steel sheet metal; where material other than steel is used for the outer shell, the thickness
2 2
should be selected so as to result in a minimum mass per unit area of 10 kg/m to 15 kg/m ;
� absorbent lining on the inside: 50 mm mineral wool;
� perforated plate covering the absorbent lining:W 30 % open;
� safety glass pane for windows: 6 mm thick.
NOTE For the sake of brevity, the term "mineral wool" has been chosen throughout this International Standard to denote
"mineral wool or fibre glass".
A typical spectrum of the sound pressure level close to a machine with and without such an enclosure is shown in
Figure 3. The maximum A-weighted sound emission around 500 Hz determines the A-weighted sound pressure
insulation.
Special requirements for enhanced low-frequency insertion loss, protective covers on the mineral wool, use of
particular shapes and materials for the impervious surface, and the absorbing material, etc. need detailed
investigations.
4.3.3 Devote full attention to leaks and openings. Avoid leaks between panels by making use of special single or
double sealing constructions, depending on the acoustic requirements. If the panels are frequently removed, make
sure that the sealing constructions can be used repeatedly. Where leaks are unavoidable, as in sliding doors, use
absorbing linings or slot silencers. Minimize all openings for ventilation, cables, pipes, transport of material, etc. and
equip them with silencers or sound-absorbent lined tunnels. Openings for maintenance purposes shall be closed
carefully during operation.
4.3.4 To avoid flanking transmission of structure-borne sound, the sound source should be mounted on resilient
elements. Panels making up the enclosure should not make contact with the sound source. Where this is
unavoidable, the number of mounting points should be kept to a minimum and these should be provided with
resilient elements between the sound source and contact points.
6 © ISO 2000 – All rights reserved
ISO 15667:2000(E)
Key
1 Outer shell
2 Absorbent lining
3 Perforated cover
4 Space for sound source of work station
5 Window
Figure 2 — Acoustic enclosure or cabin (schematic)
Figure 3 — Typical example of A-weighted octave-band spectrum of sound pressure level close to a
machine
4.3.5 To avoid flanking transmission of airborne sound via the floor, use enclosures fully enveloping the machine,
if necessary for a particularly high acoustical performance.
4.3.6 Coat the panels with damping material to increase the weight-dependent sound reduction index (or
transmission loss) and the attenuation of free bending waves, if necessary for special applications.
ISO 15667:2000(E)
5 Types of enclosures and cabins and particular requirements
5.1 Enclosures
5.1.1 Small enclosures (hoods)
Enclosures may be considered as being small for low-frequency sound when the largest dimension is less than
one-quarter of the wavelength of airborne sound. Low-mass walls and transparent walls allow for easy handling,
appropriate use and long life. The supporting structure is often the frame of the machine.
At low frequencies, the insertion loss of an airtight enclosure is
F I
Cv
G J
D��20lg 1 dB (3)
W
n
G J
C
wi
�
H K
i=1
where
CV� /(�P ) is the compliance of the gas volume inside the enclosure, in metres to the fifth power per
v 00
newton, m /N;
V is the volume of the gas inside the enclosure, in cubic metres, m ;
� is the ratio of the specific heats of the gas inside the enclosure; for air� =1,4;
P is the static pressure of the gas inside the enclosure, in pascals, Pa; for air under ambient
conditions P =10 Pa;
CV�� /p is the volume compliance of the ith enclosure panel in response to the sound pressure inside
wpii
the enclosure, in metres to the fifth power per newton, m /N;
�V is the volume displacement of the ith enclosure panel in response to the sound pressure
pi
inside the enclosure, in cubic metres, m ;
p is the uniform sound pressure inside the enclosure, in pascals, Pa;
n is the number of panels forming the enclosure.
For the special case of a cubical enclosure with clamped flat panels, the insertion loss is
L O
h E
F I
D��20lgM1 41 P dB (4)
G J
W
H K
a �P
M P
N Q
where
h is the panel thickness of the enclosure, in metres, m;
a is the edge length of the enclosure, in metres, m;
E is Young's modulus for the panel material in pascals, Pa;
�,P are as in equation (3).
8 © ISO 2000 – All rights reserved
ISO 15667:2000(E)
For simply supported rather than clamped panel edges, the insertion loss is typically 10 dB lower. For small
enclosures of the same mass, equation (4) indicates that aluminium and glass are superior to steel by more than
10 dB in insertion loss, while lead is a very poor choice for low-frequency sound [1].
Except for special constructions, all small enclosures are likely to have leaks and do not provide a positive insertion
loss at frequencies below 1,4 f , where for a cubicle enclosure with a round opening
L
c �
f � (5)
L
n
2� F I
C
� wi
i�1
G J
()hh���a 1
G J
C
v
H K
where
c is the speed of sound in the air volume inside the enclosure, in metres per second, m/s;
� is the leak ratio;
ah, are as in equation (4);
�ha� 16, is the end correction for both ends of the opening in the enclosure, in metres, m;
L
a is the radius of the opening in the enclosure, in metres, m;
L
CC, are as in equation (3).
wiv
At frequencies above f , the insertion loss of the leaky enclosure approaches that of the sealed enclosure. Leaks
L
between the enclosure and the frame should be sealed by resilient strips suitable for frequent use. Since efficient
silencers cannot be installed due to lack of space, openings should be kept as small as possible. Flanking
transmission of structure-borne sound (e.g. via paper from a mechanical printer) shall be controlled, preferably by
vibration damping.
5.1.2 Enclosures for single stationary machines
5.1.2.1 In workshops
The size of an enclosure is often determined by the available space around the machine. In some cases it may be
considered that a partial enclosure, surrounding the dominant sound source, is more suitable.
The size and construction of the enclosure needs to be chosen by taking into consideration many aspects including
the need for access, maintenance, adjustments, or removal/replacement of tools, etc. In some cases the size and
mass of individual panels may require stiffening and the provision of hooks to accommodate lifting and removal.
Additionally, enclosures may need to be treated externally to resist the effects of the environment, e.g. the effects
of oil and water. They should also be capable of being cleaned. The internal surfaces of the enclosure and all
openings should be provided with absorbent linings. These linings can be protected from the ingress of oil and
water by the provision of plastic films or metal foils. Where these coverings are used, it must be appreciated that in
some cases the coverings may affect the acoustical performance of the absorbent linings, especially at high
frequencies.
NOTE 1 For an area-related mass of film or foil of more than 50 g/m , or a thickness of plastic film of more than 50 �m,
reduced absorption occurs at frequencies above 2 kHz.
For protection of the absorptive lining from mechanical damage, sound-transparent covers are necessary.
NOTE 2 Sufficient sound transparency is generally obtained by use of aluminium mesh or perforated steel plate, 30 % open
area, and with holes of 3 mm to 5 mm diameter.
ISO 15667:2000(E)
When films or foils are used together with perforated plate, care is needed to avoid reduced sound absorption due
to sticking of the film or foil to the perforated plate. This can be achieved by having a thin, open mesh between the
perforated plate and the film. Care is needed to ensure that burrs on the inside of the perforated plate do not
puncture the thin film.
For acoustic enclosures designed for a weighted sound power insulation of at least 20 (30) dB, all leaks resulting in
a leak ratio of more than 0,01 (0,001) shall be sealed, for example by elastomeric strips and bushings (see Figures
A.3 to A.6 and A.17 to A.21). Doors require special attention (see Figures A.11 to A.13). Sound leakage due to
resonance in an extended leak may result in reduced sound insulation over a narrow frequency range.
Depending on the required performance of the enclosure, silencers shall be provided for natural and forced draught
ventilation systems and for openings needed for material flow (see Figures A.7 to A.10). For the specification and
selection of silencers, see ISO 14163.
Relatively large openings are cut out in prefabricated panels for cables, mechanical transmissions, etc. After
insertion of these elements, the openings are sealed with mineral wool between sheet metal covers and with
elastomeric strips and bushings, if necessary (see Figures A.14 to A.16).
When the sound emission of the machine is mainly determined by structure-borne sound (e.g. for internal
combustion engines, water-cooled electrical motors, generators, gear boxes, compressors, or transformers) the
performance of the enclosure is often limited by flanking transmission of structure-borne sound via the supporting
structure or connections between the source and the enclosure walls. Resilient mounts on a heavy foundation and
resilient connections or bushings provide for improved noise control [10]. In critical cases, compound elastic
mounts with an additional resilient element between the machine foundation and the building floor are employed
(see Figure A.28). Then it is necessary to separate or isolate the machine foundation from the enclosure walls. In
contrast to extended single elastic mounts (see Figure A.28), compact systems of compound elastic mounts
consisting of a mass between two resilient elements may be used under a machine mounted on a stiff frame.
5.1.2.2 Outdoors
In addition to the requirements for acoustic enclosures in workshops, attention shall be paid to weather protection
of materials (achieved by galvanized and/or painted steel) and openings (achieved by appropriately shaped sheet
metal), to wind loads (achieved by increased thickness of the outer shell and/or stiffeners between the outer shell
and the inner perforate) and to sea water protection (achieved by aluminium), if required.
NOTE Flow noise should be considered for deflector hoods for ventilation systems.
To inhibit flanking transmission via the foundation of machines mounted on elastic structures, the weight of the
foundation may be increased by a concrete bedding, if structurally acceptable. Generally, there is no need for full
absorbent lining or for limitation of windows. Special safety requirements (e.g. explosion hatches) shall be fulfilled.
5.1.3 Walk-in enclosures for large machines and groups of machines
The features of a typical machine enclosure are shown in Figure 4. In addition to the requirements for acoustic
enclosures in workshops, ventilation and light inside should be available and appropriate safety features shall be
provided [e.g. a cut-out switch so that the machine cannot be started by someone outside (see also 6.2.2)].
Applications with toxic gases, moving machine parts, etc. may require special safety devices. Different noise
control may be specified in different directions resulting in different treatment of openings.
10 © ISO 2000 – All rights reserved
ISO 15667:2000(E)
Key
1 Suitably attenuated cooling air supply/discharge
2 Inspection window
3 Workpiece entry/delivery via treated feed ducts
4 Personnel door (if necessary)
5 Routine access (hinged panel)
6 Inner lining of sound absorbent material, outer skin of insulating material
7 Airtight seal
8 Demountable panel to be sealed to form airtight seal for occasional access
Figure 4 — Typical machine enclosure
Frames of windows shall be well sealed and matched in sound insulation to the window panes (see Figures A.25
and A.26).
Particular attention shall be paid to the sound transmission through slits around doors. This depends on the type of
door and the door lock. Three types of door can be distinguished:
a) sliding doors, folding doors and up-and-over doors;
b) hinged doors (with and without threshold);
c) force-activated doors.
A sliding door is used when local conditions do not provide sufficient space for the opening and closing of a hinged
door, for example for safety reasons when a traffic path runs directly in front of a personnel door. The necessary slit
of width h which is necessary to form a circumferential air gap shall be acoustically treated over a length wW 20 h
(see Figure A.13) as a replacement of a seal.
Hinged doors of an enclosure shall open outwards if the door is on an emergency route. For hinged doors without
threshold, elastic (rubber) seals are applied on three sides of the frame. The air gap between the door and the floor
should be kept as small as possible to avoid an impaired sound reduction index (or transmission loss) of the door.
Additional measures (e.g. a brush seal) provide just a marginal improvement of the sound reduction index (or
transmission loss). A slightly better performance is obtained by using sliding rubber seals on bump thresholds. The
latter are mounted on the floor and can be crossed by wheels without providing a high risk of tripping (see
Figure A.20). The main disadvantage of such seal results from wear by friction and the need for frequent
maintenance. Depending on the frequency of use, the floor seal becomes ineffective.
ISO 15667:2000(E)
Better acoustical performance is achieved by hinged doors with a threshold. The seals are effective on all four
edges of the door and avoid acoustical leaks. The disadvantage comes from the high risk that this may cause
someone to trip.
Force-activated doors for very high acoustical requirements are equipped with pneumatically or electrically
operated pressure devices for exactly controlled and equally distributed compression of the door seals which
operate after closing of the door. The process is reversed for opening of the door. First, the pressure is released
from the seals, and then the door can be opened.
Hinged doors are commonly equipped with regular latch locks. The pressure acting on the door seals depends on
the mounting precision of hinges and latch plate. For greater pressure, snail locks are employed which allow for
additional compression of the seals by a mechanical device activated from turning the door handle by another 90°.
5.1.4 High-performance enclosures
High-performance enclosures (see 6.1) are used for example, in engine test cells, transformers, compressors and
corrugating machines.
When used outdoors, enclosures (e.g. for plant equipment or complete plants) require careful weather protection,
also storm protection. For large enclosures, this is generally provided by stiffened panels strongly attached to the
supporting structure.
Flanking transmission of structure-borne sound may determine the upper limit for the insertion loss of the
enclosure. In order to meet high requirements on noise control, the flanking transmission shall be reduced,
preferably at the vibration sources if possible, or alternatively in the propagation path by means of special resilient
elements holding the panels, and finally by means of a damping layer attached to the outer shell. Double walls with
mass per unit area m��' and m�� of the two shells at a distance t and intermediate sound absorbent material (with
1 2
density of not more than 125 kg/m ) increase the sound reduction index (or transmission loss) in the frequency
range above 1,4 f ,where f is the frequency of double-wall resonance:
d d
F I
(6)
fa� �
d G J
mm�� ��t
H K
where
a� 60 Hz kg / m ;
m��and m�� are expressed in kilograms per square metre (kg/m ), and t is expressed in metres (m).
1 2
NOTE For two steel plates of 1 mm and 1,5 mm thickness at a distance of 100 mm, filled with mineral wool, the resonance
frequency is about 80 Hz.
5.1.5 Mobile and vehicle-mounted enclosures
Vehicle-mounted machinery (e.g. generators of electric power and compressed air, pumps and hydraulic systems)
requires enclosures for operation on construction sites and other temporary installations. Whilst the basic acoustic
features of such enclosures remain the same as described in 5.1.2, certain constraints lead to special
considerations.
The panel system will often be fitted to a frame which would itself flex as the vehicle passes over undulating terrain.
However, the fixture of the sheet panel system adds very con
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