SIST EN ISO 11690-2:1997
(Main)Acoustics - Recommended practice for the design of low-noise workplaces containing machinery - Part 2: Noise control measures (ISO 11690-2:1996)
Acoustics - Recommended practice for the design of low-noise workplaces containing machinery - Part 2: Noise control measures (ISO 11690-2:1996)
Migrated from Progress Sheet (TC Comment) (2000-07-10): BTS4 by RES BTS4 C1/1992 approved new target dates as requested by CEN/TC 211 ++ for the launching of the parallel voting procedure.
Akustik - Richtlinien für die Gestaltung lärmarmer maschinenbestückter Arbeitsstätten - Teil 2: Lärmminderungsmaßnahmen (ISO 11690-2:1996)
Dieser Teil von ISO 11690 befasst sich mit technischen Gesichtspunkten der Lärmminderung in Arbeitsstätten. Es werden die verschiedenen technischen Massnahmen angegeben, die entsprechenden akustischen Grössen beschrieben, das Ausmass der Lärmminderung diskutiert und die Nachprüfverfahren grob beschrieben. Dieser Teil von ISO 11960 befasst sich ausschliesslich mit Hörschall. Anmerkung 1: Anhang K enthält eine Auflistung von internationalen Normen und anderer Literatur zur Lärmminderung.
Acoustique - Pratique recommandée pour la conception de lieux de travail a bruit réduit contenant des machines - Partie 2: Moyens de réduction du bruit (ISO 11690-2:1996)
La présente partie de l'ISO 11690 traite des aspects techniques de la réduction du bruit sur les lieux de travail. Les différents moyens techniques sont donnés, les grandeurs acoustiques liées décrites, la valeur de la réduction du bruit discutée et les méthodes de vérification esquissées. La présente partie de l'ISO 11690 ne traite que des sons audibles.
NOTE 1 L'annexe K donne la liste des Normes internationales et autres publications relatives aux moyens de réduction du bruit.
Akustika - Priporočena praksa za oblikovanje tihih delovnih mest - 2. del: Ukrepi za obvladovanje hrupa (ISO 11690-2:1996)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 11690-2:1997
01-april-1997
$NXVWLND3ULSRURþHQDSUDNVD]DREOLNRYDQMHWLKLKGHORYQLKPHVWGHO 8NUHSL]D
REYODGRYDQMHKUXSD ,62
Acoustics - Recommended practice for the design of low-noise workplaces containing
machinery - Part 2: Noise control measures (ISO 11690-2:1996)
Akustik - Richtlinien für die Gestaltung lärmarmer maschinenbestückter Arbeitsstätten -
Teil 2: Lärmminderungsmaßnahmen (ISO 11690-2:1996)
Acoustique - Pratique recommandée pour la conception de lieux de travail a bruit réduit
contenant des machines - Partie 2: Moyens de réduction du bruit (ISO 11690-2:1996)
Ta slovenski standard je istoveten z: EN ISO 11690-2:1996
ICS:
13.140 Vpliv hrupa na ljudi Noise with respect to human
beings
17.140.20 Emisija hrupa naprav in Noise emitted by machines
opreme and equipment
SIST EN ISO 11690-2:1997 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 11690-2:1997
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SIST EN ISO 11690-2:1997
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SIST EN ISO 11690-2:1997
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SIST EN ISO 11690-2:1997
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SIST EN ISO 11690-2:1997
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SIST EN ISO 11690-2:1997
INTERNATIONAL IS0
STANDARD 11690-2
First edition
1996-l I-01
Acoustics - Recommended practice for
the design of low-noise workplaces
containing machinery -
Part 2:
Noise control measures
Acoustique - Pratique recommandke pour la conception de lieux de travail
2 bruit rkduit contenant des machines -
Partie 2: Moyens de kduction du bruit
Reference number
IS0 11690-2: 1996(E)
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SIST EN ISO 11690-2:1997
IS0 11690=2:1996(E)
Page
Contents
1
1 Scope .
................................................................... 1
2 Normative reference
1
3 Definitions .
............................................. 1
4 Technical aspects of noise control
............................................................... 2
5 Noise control at source
...................................... 6
6 Noise control on the transmission path
8
7 Noise control at the work station .
8
8 Verification methods .
9 New technologies . 10
Annexes
................ 11
A Modification or replacement of machine components
.................................................. 12
B Arrangement of sound sources
.................................................................................. 13
C Enclosures
15
D Silencers .
.......................................... 16
E Noise barriers and screens in rooms
................................................ 17
F Acoustical treatment of surfaces
................................................ 19
G Structure-borne sound insulation
20
H Airborne sound insulation of partitions .
21
I Noise control at the work station .
..................................................... 22
J Example of a new technology
................................................................................ 24
K Bibliography
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
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SIST EN ISO 11690-2:1997
IS0 11690=2:1996(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 liaison 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 11690-2 was prepared by Technical Committee
ISOmC 43, Acoustics, Subcommittee SC 1, Noise.
IS0 11690 consists of the following parts, under the general title Acous-
tics - Recommended practice for the design of low-noise workplaces
containing machinery:
Par? I: Noise control strategies
Part 2: Noise control measures
- Part 3: Sound propagation and noise prediction in workrooms
Part 1 is the central document in the series. Parts 2 and 3 give additional
technical and explanatory information. It is therefore recommended to start
with part 1.
Annexes A to K of this part of IS0 11690 are for information only.
. . .
III
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E) @ IS0
Introduction
Most of the existing International Standards prepared in lSO/TC 43/SC 1
specify methods for measurement and/or evaluation of noise. The final
objective of IS0 11690, however, is noise reduction.
A number of noise control measures are offered. However, in order to be
effective, the most appropriate noise control measure(s) should be chosen
for a given situation.
It is important when non-acoustic engineers are involved in noise control
practice for these engineers to have a basic knowledge of noise emission
and propagation characteristics and to understand the basic principles of
noise control.
To assist in the development of noise control in the workplace, it is essen-
tial that the information contained in these recommended practices is dis-
seminated through International Standards.
In order to reduce noise as a hazard in the workplace, individual countries
have produced national legislation. Generally, such national legislation
requires noise control measures to be carried out in order to achieve the
lowest reasonable levels of noise emission, noise immission and noise ex-
posure, taking into account:
known available measures;
the state of the art regarding technical progress;
- the treatment of noise at source;
- appropriate planning, procurement and installation of machines and
equipment.
This part of IS0 11690, together with the two other parts in the series, out-
lines procedures to be considered when dealing with noise control at
workplaces, within workrooms and in the open. These recommended prac-
tices give in relatively simple terms the basic information necessary for all
parties involved in noise control in workplaces and in the design of low-
noise workplaces to promote the understanding of the desired noise control
requirements.
The purpose of the IS0 11690 series is to bridge the gap between existing
literature on noise control and the practical implementation of noise control
measures. In principle, the series applies to all workplaces and its main
function is:
- to provide sim ple, brief info rmation on some aspects of noise control
in
workplaces;
- to act as a guide to help in the understanding of requirements in stan-
dards, directives, text books, manuals, reports and other specialized
technical documents;
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SIST EN ISO 11690-2:1997
@ IS0 IS0 11690=2:1996(E)
to provide assistance in decision making when assessing the various
-
measures available.
The IS0 11690 series should be useful to persons such as plant person-
nel, health and safety officers, engineers, managers, staff in planning and
purchasing departments, architects and suppliers of plants, machines and
equipment. However, the above-mentioned parties should keep in mind
that adherence to the recommendations of the IS0 11690 series is not all
that is necessary to create a safe workplace.
The effects of noise on health, well-being and human activity are many. By
giving guidelines for noise control strategies and measures, the IS0 11690
series aims at a reduction of the impact of noise on human beings at
workplaces. Assessment of the impact of noise on human beings is dealt
with in other documents.
V
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SIST EN ISO 11690-2:1997
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E)
INTERNATIONAL STANDARD 0 IS0
Acoustics - Recommended practice for the design of low-noise
workplaces containing machinery -
Part 2:
Noise control measures
1 Scope 3 Definitions
For the purposes of this part of IS0 11690, the defini-
This part of IS0 11690 deals with the technical
tions given in IS0 11690-I apply.
aspects of noise control in workplaces. The various
technical measures are stated, the related acoustical
quantities described, the magnitude of noise reduction
discussed and the verification methods outlined.
4 Technical aspects of noise control
This part of IS0 11690 deals only with audible sound.
Noise reduction measures can be applied at source
(emission), between the source and the receiver
NOTE 1 Annex K lists relevant International Standards
(transmission path), and at the work station (receiver).
and other literature on noise control measures.
(See figure 1.)
When dealing with the noise emission of a machine, an
installation or a production process, etc., all possible
noise reduction measures should be considered (see
clause 5 and IS0 11690-l). To determine whether
noise emission is as low as reasonably practicable, it
2 Normative reference
is necessary to consider noise emission quantities;
these are given in the noise emission declaration (see
The following standard contains provisions which,
IS0 11690-I :1996, clause 8) or determined by meas-
through reference in this text, constitute provisions of
urements (carried out in compliance with the relevant
this part of IS0 11690. At the time of publication, the
standard).
edition indicated was valid. All standards are subject to
revision, and parties to agreements based on this part
An assessment of noise control devices such as en-
of IS0 11690 are encouraged to investigate the
closures, partial enclosures, barriers and screens, si-
possibility of applying the most recent editions of the
lencers, etc. can be carried out by using, for example,
standards indicated below. Members of IEC and IS0
the insertion loss data (see 6.2).
maintain registers of currently valid International Stan-
dards.
The acoustic quality of workrooms and buildings is as-
sessed with reference to the sound insulation regard-
ing airborne and structure-borne sound (see 6.4), and
IS0 11690-l :I 996, Acoustics - Recommended prac-
that of workrooms with reference to sound propagation
tice for the design of low-noise workplaces containing
parameters (see 6.3).
machinery - Part I: Noise control strategies.
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E) @ IS0
Receiving point
c
Noise source Transmission path
(work station)
. , 0.
(Secondary noise controt)
(Primary noise control)
Figure 1 - Basic aspects of noise control
The overall effectiveness of noise control measures is and machines. They should be implemented at the
design stage because retrospective measures can
determined from the noise immission values at the
work stations. affect operational requirements and are generally
more expensive. However, they are also recom-
Generally, people located at a work station or in the
mended for existing noise sources, when practicable.
vicinity of a machine are affected by the direct noise
emitted by the machine. Therefore, to reduce noise in
Noise control at source in workplaces deals in particu-
the workplace, the most effective solution is to reduce
lar with the noise reduction of existing machines, the
noise at source (primary measures). Additional meas-
development and selection of low-noise working proc-
ures on the transmission paths (secondary measures)
esses and production technologies, the replacement
may be impractical because they hinder the work task
of machine parts and the assessment of the results
and the production process. When assessing the state
obtained.
of noise reduction technology, low noise emission of
sound sources is therefore given high priority with re-
The effectiveness of noise control at source is based
gard to occupational safety.
on measurements and is assessed by comparison
with the noise emission data, for example, provided by
The basic aspects of noise control (see also
the supplier/manufacturer (see IS0 11690-I :I 996,
IS0 11690-I) are illustrated in figure 1. These are
clause 8).
reviewed in clauses 5 to 7.
In order to minimize noise at the workplace, all noise
control measures should be considered a priori (see
5.2 Noise control at source by design
figure 2).
When machine noise (or noise from technical produc-
Noise control is most effective if it is carried out when
tion equipment) is considered, two types of noise gen-
planning, modifying, changing existing machinery or
eration should be distinguished: fluid dynamic noise
equipment, or when acquiring new machinery or
generation (gas and/or liquid) and mechanical genera-
equipment in plants, workrooms and buildings. From
tion.
the outset, all parties involved (see IS0 11690-I :I 996,
clause 6) and, in particular, the noise experts, should
Fluid dynamic noise arises from temporary fluctuations
take part in the process. Noise control measures are
in pressure and velocity of fluids. Examples are com-
most effective if they are integrated at the design
bustion processes, fans, blow-out openings and
stage of machines, production processes, workrooms
hydraulic systems.
and tasks (see IS0 11690-I :I 996, clause 7). Machine
operation, material transport, safety technology, ergo-
Mechanically generated noise is caused by vibrations
nomics and environmental protection should also be
of machine components that are excited by dynamic
considered at that stage.
forces which are generated, for example, by impacts
or out-of-balance masses. The vibrations are transmit-
ted to noise-radiating surfaces, such as machine cas-
5 Noise control at source
ing, workpieces, etc. Examples are tooth-wheel gears,
electric motors, hammers, shakers and mechanical
presses (see figure 3).
5.1 General
The meas ure 1s described in this clause deal with the In order to control noise at source, the noise-
generation mechanism should be taken into account.
redu ction of noise generated by working processes
2
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E)
@ IS0
Noise control
A
/ \ f
Use of noise control measures on the Use of noise control at the
Use and development of low-
transmission path work station
noise emission technology
Airborne noise - cabins
- seLection and use of low-noise
- location of source - screens
working process
- enclosures - breaks in quiet environment
- mufflers
- selection and use of low-noise
- absorptive treatment
machinery
- screens
- partitions, etc.
Structure-borne noise
- vibration isolation
- floating floors
- construction joints of buiCding elements, etc.
- Steps for the implementation of noise control measures
Figure 2
Radiation
Excitation Transmission
b) reduction of the vibrational velocity of the machine
structure at the excitation point for a given dy-
namic force [e.g. by means of stiffeners or addi-
tional masses (inertia blocks)];
c) reduction of the vibration (structure-borne sound)
transmission from the excitation point to the
sound-radiating surfaces [e.g. by using elastic
elements and materials with high internal damping
(cast iron)];
d) reduction of the sound radiated by a vibrating
structure, for example by use of
- thin walls with ribs instead of thick stiff walls,
- damping layers on thin metal sheets,
- perforated metal sheets (provided noise insu-
lation is not required);
e) sound-insulating wrappings or thick-walled struc-
Figure 3 - Generation process of mechanical
tures (thin damped metal sheets near the radi-
noise
ating surface).
Further information on noise reduction at source can
Examples of reduction of fluid dynamic noise are the
be found in ISO/TR 11688-l and ISOTTR 11688-2.
following:
reduction of periodical pressure fluctuations at the
a)
excitation source;
5.3 Information on noise emission
b) reduction of flow velocities;
In addition to the information on noise emission given
avoidance of sudden changes in pressure;
C)
by suppliers/manufacturers in technical documentation
d) effective design of through-flow components.
(see IS0 11690-I 3996, clause 8), there may be
measures specific to industrial sectors. Information on
Examples of reduction of mechanically generated
such measures can be found in databases, profes-
noise are the following:
sional magazines, trade association journals, etc.
a) reduction of exciting dynamic forces (e.g. by
For some machine families, there are lists of noise
means of elastic layers to extend the impulse
emission data obtained under specified operating
duration of impacts);
3
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SIST EN ISO 11690-2:1997
@ IS0
IS0 11690-2: 1996(E)
machine and noise radiation by the machine surface,
conditions. These lists can help purchasers select low-
without affecting performance. Annex A gives exam-
noise machines/equipment (see IS0 11690-l :1996,
ples of such noise reduction measures.
annex A).
5.4 Use of low-noise machines
5.6 Low-noise working and production
In some circumstances, rather than implementing technologies
costly retrospective noise control measures, it is feas-
ible to replace a noisy unit in a plant with a low-noise
It is always beneficial, if feasible, to replace a particu-
one (see table 1).
larly noisy machine or unit in a plant with a quieter
one, for example by using a machine that works to a
There are also noisy operations which are not con-
different principle (e.g. replacing an impact screw-
nected with fixed machines, for example from the use
driver by a continuous direct-driven screwdriver).
of hand-held tools. These can often be the dominating
noise sources in a workroom. If care is taken in select-
With regard to existing processes, particular attention
ing the tools or the working arrangement (e.g. sound-
should be paid to the possibility of substituting the
deadened hammers, cushioned work tables, low-noise
process with an equally effective but quieter method.
grinding discs, magnetic damping mats, etc.), consid-
erable noise reductions can be achieved as shown in
When substituting a production process, low-noise
figures 4 to 7.
alternatives should be systematically searched for.
5.5 Modification or replacement of machine
The successive replacement of machines, plant items
and processes by less noisy ones will in the long term
components
lead to quieter working environments even though low-
noise machines have to be positioned alongside exist-
It is possible, by replacing or modifying machine
ing noisy ones.
components, to reduce noise transmission inside the
Table 1 - Examples of alternative processes with lower noise
Low-noise processes
High-noise processes
Compression and roll riveting
Percussion riveting
Electrical drive
Drive by compressed air or internal combustion engine
Use of machines that can be fitted with drills or circular saw
Cutting or making holes in, for example, stone or concrete
by the use of pneumatic or internal combustion percussive blades equipped with diamond teeth
machines
Tapering/full-forward extrusion
Heading in the die
Pull cutting
Push cutting
Radiation drying
Flow drying
Plasma cutting under water
Plasma oxygen cutting
Laser-beam cutting
Cutting shock, punching
Conventional TIG/TAG welding TIGTTAG shielded arc welding
Laser-beam hardening
Flame-hardening
Pressure fixing
Fastening with rivets
Stroke forming , Hydraulic pressing
Seam welding
Spot welding
NOTES
1 A change of the material and/or form of the component under manufacture may allow the use of low-noise production processes.
2 This list is by no means exhaustive.
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E)
a) Conventional steel hammer
L p,?, = 115 dB
b) Sound-deadenedhammer (with litle recoil)
L /,A = 10TdB
4 000
125 250 500 1000
2 000 8 000
Octave-bandfrequency,Hz
Figure 4 - Example of sound pressure level during hammering
110
M
D
w
5
.-
G 100
t
v)
Y
k
3
E 90
c
ru
Tii
z
A
CIJ
125 250 500 1000 4 000
a 000
2 000
Octave-band frequency,Hz
Figure 5 - Example of sound pressure level when grinding
during the cleaning of a cast iron electromotor housing
5.7 Maintenance of machines and noise maintained at all times. Any maintenance defect nor-
mally increases the noise levels.
control devices
Noise emission levels from machines or processes
can be unnecessarily high due to lack of maintenance,
Maintenance of noise control devices is also of prime
poor lubrication, misalignment, unbalanced and loose
importance. Therefore the function of enclosures,
parts, etc. Optimum operating conditions should be
screens and silencers should be carefully monitored.
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E)
a) Steel working plate, 25 mm thick
b) Steel working pLate, damped by viscous
material, 40 mm thick
c) Steel working plate, 200 mm thick
<
80
a) b) cl
Figure 6 - Example of sound pressure level when hammering
a) Without magnetic mat
L pA = 111 dB
b) With magnetic mat
L p/j =102 dB
125 250 500 1000 4000
2000 8 000
Octave-band frequency, Hz
Example of sound pressure level when grinding a steel plate
Figure 7 -
6.2 Use of noise control devices
6 Noise control on the transmission path
Enclosures (see annex C), silencers (see annex D)
6.1 Noise control by means of a proper
and screens (see annex E) can be effective measures
spatial arrangement of the noise sources
for the reduction of the noise emitted from machines,
installations, piping systems and openings.
An optimized spatial arrangement of machines can
provide a substantial noise level reduction at work sta-
tions. This is mainly applicable when planning new An enclosure is a structure completely surrounding the
plants and installations but should also be considered machine or installation. It consists mainly of a sound-
for existing plants.
insulating shell (metal, wood, concrete, etc.) with an
internal sound-absorbing lining. The achievable noise
Noise reduction can be obtained by increasing the
reduction depends on the insulation of airborne sound
distance between the noise sources and the work sta- provided by the shell and on the degree of absorption
tions (see annex B).
by the internal surface of the enclosure. In practice, it
6
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E)
@ IS0
The acoustical quality of a room is high if DLf is low
is limited by openings, ineffective seals and by trans-
mission of structure-borne sound. This limitation can and DL2 is high. Typical values for average sound ab-
sorption coefficient and for sound propagation param-
be minimized by using measures such as silenced
openings. eters DL2 and DLf are given in table 2 for different
types of rooms and surface treatments.
The effectiveness of noise control by using enclo-
sures, silencers or screens can be measured and as- Generally, industrial noise lies in the frequency range
500 Hz to 2 000 Hz. In such situations, the following
sessed by the insertion loss, the transmission loss and
the reduction of sound level (see IS0 11690-l :I 996, reductions in sound pressure level relative to rooms
with hard walls and ceiling may be achieved.
clause 3, for definitions).
a) In the near region, the reduction of the A-weighted
sound pressure level is in the range 1 dB to 3 dB
6.3 Noise control by use of sound-absorbing
because surface treatment has very little effect
materials
(see IS0 11690-l for definitions).
The relationship between noise emission and noise
b) In the middle region, this reduction is usually be-
immission is determined by sound propagation (see
tween 3 dB and 8 dB.
IS0 11690-3). Sound propagation and therefore the
c) In the far region, it usually lies between 5 dB and
acoustical quality of a room are influenced by the
treatment of surfaces (ceiling and walls) by using 12 dB, depending on the room dimensions and
sound-absorbing materials, which should be selected the extent of wall treatment and fittings.
in relation to the frequency spectrum of the noise. For
attenuation of noise at low frequencies, the use of ab- In order to assess the effectiveness of a surface
treatment outside the direct field, distinction should be
sorptive materials is less effective.
made between rooms with and without diffuse field
conditions (see IS0 11690-I for definitions and also
Noise in rooms consists of direct noise from sources
and reflected noise from room boundaries (floors, annex F and IS0 11690-3).
walls, ceilings, other equipment, fittings, etc.). Absorp-
tive surface treatment reduces exclusively the re- Typical spatial sound distribution curves in rooms of
flected noise. different shapes and sizes before and after installation
of a variety of surface treatments are given in figures 8
It is possible to assess the acoustical quality of a room and 9.
and therefore the effectiveness of a surface treatment
by using the sound propagation quantities, e.g. the The combination of surface treatment and noise barri-
rate of spatial decay (DL2) and the excess (DLf) of ers is normally quite effective and leads to a noise
level reduction which is substantially higher than that
sound pressure levels. These quantities are derived
from the spatial sound distribution curves (see obtained with only one of these measures (see an-
IS0 11690-I for definitions and also ISO/TR 11690-3). nexes E and F). In addition to the noise reduction
Recommended values of DL2 are given in which can be measured objectively, there will be an
IS0 11690-I :I 996, table 3 (see also table 2 of this important subjective improvement.
part of IS0 11690). The assessment can be made
from quantities measured (see clause 8) or calculated More information on surface treatment is given in an-
nex F.
using noise-prediction methods (see IS0 11690-3).
Table 2 - Typical values for the average sound absorption coefficient (a) and sound propagation
descriptors DLf and DL2 in the middle region
DLf DL2
a
Description of rooms
dB
dB
With small/intermediate volume (V c 10 000 m3 and h < 5 m)
< 0,2
8to13 1 to3
without absorbing ceiling, empty
I With absorbing large ceiling, volume with (V fittings 3 10 000 m3 and h 2 5 m) without < 0,2 6 to 9 2,5 to 4
All rooms with absorbing ceiling, with fittings > 0,3
5 to 8 3,5 to 5
NOTE - DLf is the excess of sound pressure level. DL2 is the rate of spatial decay of sound pressure levels per distance doubling. See
IS0 11690-l for definitions.
I
7
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SIST EN ISO 11690-2:1997
IS0 11690-2: 1996(E)
t
m
u
h
4
-
A
F
aJ
-
aJ
100
10
Distance from source, m -
- Reflecting floor, walls and ceiling
- With absorption at ceiling
- With absorption at ceiling and walls
-mmmwwmmmmmmm.
Without reflections (free field)
NOTE - All three dimensions of the room are of the same order of magnitude.
Figure 8 - Typical spatial sound distribution curve for a room with diffuse field conditions,
without and with several surface treatments
8 Verification methods
6.4 Sound propagation in structures
and noise control measures
8.1 General
Transmission of airborne noise into adjacent rooms
or into the open is reduced by increasing the sound
Sound sources, noise control devices, sound propa-
insulation of walls, ceilings, windows and doors (see
gation, noise levels in workplaces and sound insula-
annex H).
tion of buildings are described by acoustical quantities.
These acoustical quantities and sound level reduc-
Propagation of structure-borne sound should be pre-
tions by means of specific measures are frequently
vented initially as it is very difficult to eliminate once in
determined or agreed upon in plans, programmes and
the structure. Measures to reduce the transmission of
contracts. The value of these acoustical quantities and
airborne and structure-borne sound (see annexes G
the success of
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Questions, Comments and Discussion
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