Acoustics - Measurement of sound insulation in buildings and of building elements - Part 18: Laboratory measurement of sound generated by rainfall on building elements (ISO 140-18:2006)

This part of ISO 140 specifies a laboratory method of measurement of the impact sound insulation of roofs, roof/ceiling systems and skylights excited by artificial rainfall. The results obtained can be used for assessing the noise to be produced by rainfall on a given building element in the room or space below. The results can also be used to compare rainfall sound insulation capabilities of building elements and to design building elements with appropriate rainfall sound insulation properties. This part of ISO 140 is based on measurements with artificial raindrops under controlled conditions using a water tank in a laboratory test facility in which flanking sound transmission is suppressed. Measurements using real rain, although a useful means for validation purposes, are not included because of the variable, unpredictable and intermittent nature of real rain. Other mechanical simulation methods under investigation by researchers are not sufficiently well developed at present to adequately simulate real rain both in terms of sound levels and spectra generated.

Akustik - Messung der Schalldämmung in Gebäuden und von Bauteilen - Teil 18: Messung des durch Regenfall auf Bauteile verursachten Schalls im Prüfstand (ISO 140-18:2006)

Dieser Teil von ISO 140 legt ein Laborverfahren zum Messen der Körperschalldämmung von Dächern, Dach/Decken-Systemen und Oberlichtern bei künstlicher Beregnung fest. Die erhaltenen Ergebnisse können zur Bewertung des durch Niederschlag auf ein gegebenes Bauteil im Raum oder den darunter liegenden Bereich erzeugten Geräuschs verwendet werden. Des Weiteren können die Ergebnisse zum Vergleich des Regenschalldämm-Vermögens von Bauteilen und zur Konstruktion von Bauteilen mit angemessenen Regenschalldämm-Eigenschaften verwendet werden.
Dieser Teil der ISO 140 beruht auf Messungen mit künstlich erzeugten Regentropfen unter geregelten Bedingungen unter Verwendung eines Wassertanks in einer Laborprüfeinrichtung, in der die Flankenübertragung des Schalls unterdrückt ist. Messungen mit natürlichem Regen werden, auch wenn sie für Validierungszwecke nützlich wären, aufgrund der veränderlichen, unvorhersehbaren und diskontinuierlichen Eigenschaften des natürlichen Regens nicht behandelt. Andere mechanische Simulationsverfahren werden von Forschern untersucht, sind jedoch zum derzeitigen Standpunkt nicht ausreichend genug entwickelt, um natürlichen Regen sowohl hinsichtlich des erzeugten Schallpegels als auch des Schallspektrums adäquat zu simulieren.

Acoustique - Mesurage de l'isolation acoustique des immeubles et des éléments de construction - Partie 18: Mesurage en laboratoire du bruit produit par la pluie sur les éléments de construction (ISO 140-18:2006)

L'ISO 140-18:2006 spécifie une méthode de mesurage en laboratoire de l'isolement acoustique aux bruits de choc des toits, toitures/plafonds et fenêtres de toit soumis à une excitation par une pluie artificielle. Les résultats obtenus peuvent servir à évaluer le bruit produit par la pluie sur un élément de construction donné dans la salle ou l'espace inférieur. Ils peuvent également être utilisés pour comparer les performances d'isolement acoustique à la pluie des éléments de construction et pour concevoir des éléments de construction dont les propriétés d'isolement acoustique à la pluie sont appropriées.
L'ISO 140-18:2006 est basée sur les mesurages effectués avec une pluie artificielle dans des conditions maîtrisées, en utilisant un réservoir d'eau monté sur un local d'essai sans transmissions latérales. Bien que les mesurages effectués avec la pluie réelle constituent un moyen utile utilisé à des fins de validation, ils ne sont pas inclus dans l'ISO 140-18:2006 en raison de la nature variable, imprévisible et intermittente de la pluie réelle. Les autres méthodes de simulation mécaniques étudiées par les chercheurs ne sont actuellement pas suffisamment développées pour simuler de manière adéquate la pluie réelle, à la fois en termes de niveaux acoustiques et de spectres générés.

Akustika - Merjenje zvočne izolirnosti v stavbah in zvočne izolirnosti gradbenih elementov - 18. del: Laboratorijsko merjenje zvoka, ki ga padavine povzročajo na gradbenih elementih (ISO 140-18:2006)

General Information

Status
Withdrawn
Publication Date
28-Feb-2007
Withdrawal Date
31-Aug-2020
Technical Committee
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
25-Aug-2020
Due Date
17-Sep-2020
Completion Date
01-Sep-2020

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SLOVENSKI STANDARD
SIST EN ISO 140-18:2007
01-marec-2007
$NXVWLND0HUMHQMH]YRþQHL]ROLUQRVWLYVWDYEDKLQ]YRþQHL]ROLUQRVWLJUDGEHQLK
HOHPHQWRYGHO/DERUDWRULMVNRPHUMHQMH]YRNDNLJDSDGDYLQHSRY]URþDMRQD
JUDGEHQLKHOHPHQWLK ,62
Acoustics - Measurement of sound insulation in buildings and of building elements - Part
18: Laboratory measurement of sound generated by rainfall on building elements (ISO
140-18:2006)
Akustik - Messung der Schalldämmung in Gebäuden und von Bauteilen - Teil 18:
Messung des durch Regenfall auf Bauteile verursachten Schalls im Prüfstand (ISO 140-
18:2006)
Acoustique - Mesurage de l'isolation acoustique des immeubles et des éléments de
construction - Partie 18: Mesurage en laboratoire du bruit produit par la pluie sur les
éléments de construction (ISO 140-18:2006)
Ta slovenski standard je istoveten z: EN ISO 140-18:2006
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
91.120.20 $NXVWLNDYVWDYEDK=YRþQD Acoustics in building. Sound
L]RODFLMD insulation
SIST EN ISO 140-18:2007 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN ISO 140-18:2007

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SIST EN ISO 140-18:2007
EUROPEAN STANDARD
EN ISO 140-18
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2006
ICS 91.120.20

English Version
Acoustics - Measurement of sound insulation in buildings and of
building elements - Part 18: Laboratory measurement of sound
generated by rainfall on building elements (ISO 140-18:2006)
Acoustique - Mesurage de l'isolation acoustique des Akustik - Messung der Schalldämmung in Gebäuden und
immeubles et des éléments de construction - Partie 18: von Bauteilen - Teil 18: Messung des durch Regenfall auf
Mesurage en laboratoire du bruit produit par la pluie sur les Bauteile verursachten Schalls im Prüfstand (ISO 140-
éléments de construction (ISO 140-18:2006) 18:2006)
This European Standard was approved by CEN on 14 November 2006.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
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: rue de Stassart, 36  B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 140-18:2006: E
worldwide for CEN national Members.

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SIST EN ISO 140-18:2007

EN ISO 140-18:2006 (E)





Foreword


This document (EN ISO 140-18:2006) has been prepared by Technical Committee ISO/TC 43
"Acoustics" in collaboration with Technical Committee CEN/TC 126 "Acoustic properties of
building elements and of buildings", the secretariat of which is held by AFNOR.

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 May 2007, and conflicting national standards
shall be withdrawn at the latest by May 2007.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.


Endorsement notice

The text of ISO 140-18:2006 has been approved by CEN as EN ISO 140-18:2006 without any
modifications.

2

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SIST EN ISO 140-18:2007


INTERNATIONAL ISO
STANDARD 140-18
First edition
2006-11-15

Acoustics — Measurement of sound
insulation in buildings and of building
elements —
Part 18:
Laboratory measurement of sound
generated by rainfall on building
elements
Acoustique — Mesurage de l'isolement acoustique des immeubles et
des éléments de construction —
Partie 18: Mesurage en laboratoire des bruits produit par la pluie sur les
éléments de construction




Reference number
ISO 140-18:2006(E)
©
ISO 2006

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
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ii © ISO 2006 – All rights reserved

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Equipment . 3
5 Test arrangement. 3
6 Classification of rain types . 4
7 Test equipment and procedure . 4
8 Expression of results . 9
9 Measurement uncertainty . 9
10 Test report . 10
Annex A (informative) Example of a tank with perforated base . 11
Annex B (informative) Reference test specimens. 14
Bibliography . 16

© ISO 2006 – All rights reserved iii

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 140-18 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 2, Buildings
acoustics.
ISO 140 consists of the following parts, under the general title Acoustics — Measurement of sound insulation
in buildings and of building elements:
— Part 1: Requirements for laboratory test facilities with suppressed flanking transmission
— Part 2: Determination, verification and application of precision data
— Part 3: Laboratory measurements of airborne sound insulation of building elements
— Part 4: Field measurements of airborne sound insulation between rooms
— Part 5: Field measurements of airborne sound insulation of façade elements and façades
— Part 6: Laboratory measurements of impact sound insulation of floors
— Part 7: Field measurements of impact sound insulation of floors
— Part 8: Laboratory measurements of the reduction of transmitted impact noise by floor coverings on a
heavyweight standard floor
— Part 9: Laboratory measurement of room-to-room airborne sound insulation of a suspended ceiling with a
plenum above it
— Part 10: Laboratory measurement of airborne sound insulation of small building elements
— Part 11: Laboratory measurements of the reduction of transmitted impact sound by floor coverings on
lightweight reference floors
— Part 13: Guidelines (Technical Report)
— Part 14: Guidelines for special situations in the field
— Part 16: Laboratory measurement of the sound reduction index improvement by additional lining
— Part 18: Laboratory measurement of sound generated by rainfall on building elements
iv © ISO 2006 – All rights reserved

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
Introduction
This part of ISO 140 prescribes a laboratory method for the measurement of sound generated by rainfall on
building elements using artificial raindrops produced by a water tank.
Ideally, one should expose the test specimen to real rain for such measurements. But real rain is neither
steady nor continuous with respect to time. Furthermore, raindrops can vary in diameter due to several factors,
including geographic location, which will introduce variability in measured values. One can, however, use real
raindrops as a means of validation of measured results obtained with artificial raindrops by building a test
room in an unobstructed location. For such research, it is important that the rain sensor or rain gauge is
capable of measuring constant short interval rainfall rates. In the absence of drop size information,
repeatability and fluctuations of the measured sound levels with real rain can be investigated by undertaking
measurements separated by a time interval of at least 24 h.
Artificial raindrop generation systems, other than the water tank used in this part of ISO 140, exist, such as
hydraulic spray nozzles; however, so far, nozzles corresponding to the specifications given in this part of
ISO 140 are not commercially available: indeed, their flow rate is too high when the drop diameter is correct or
the drop diameter is too small when the flow rate is correct. As a result, only the water tank solution is
proposed in this part of ISO 140.
An alternative to real rain or artificial raindrops is the dry mechanical excitation of the test specimen.
Researchers have used different methods, such as excitation by an impact hammer and other mechanical
impacting simulators, with an aim to simulate the noise of real rain. Such methods invariably suffer from the
drawback that the noise source does not generate both the sound levels and the sound spectra that compare
well with corresponding values generated by the real rain on various types of test specimens. Further
research work is encouraged to develop mechanical methods of rain noise generation that can match both the
sound levels and spectra of real rain.

© ISO 2006 – All rights reserved v

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SIST EN ISO 140-18:2007

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SIST EN ISO 140-18:2007
INTERNATIONAL STANDARD ISO 140-18:2006(E)

Acoustics — Measurement of sound insulation in buildings and
of building elements —
Part 18:
Laboratory measurement of sound generated by rainfall on
building elements
1 Scope
This part of ISO 140 specifies a laboratory method of measurement of the impact sound insulation of roofs,
roof/ceiling systems and skylights excited by artificial rainfall. The results obtained can be used for assessing
the noise to be produced by rainfall on a given building element in the room or space below. The results can
also be used to compare rainfall sound insulation capabilities of building elements and to design building
elements with appropriate rainfall sound insulation properties.
This part of ISO 140 is based on measurements with artificial raindrops under controlled conditions using a
water tank in a laboratory test facility in which flanking sound transmission is suppressed. Measurements
using real rain, although a useful means for validation purposes, are not included because of the variable,
unpredictable and intermittent nature of real rain. Other mechanical simulation methods under investigation by
researchers are not sufficiently well developed at present to adequately simulate real rain both in terms of
sound levels and spectra generated.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 140-1:1997, Acoustics — Measurement of sound insulation in buildings and of building elements —
Part 1: Requirements for laboratory test facilities with suppressed flanking transmission
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 3382-2, Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in ordinary
rooms
ISO 10848-1:2006, Acoustics — Laboratory measurement of the flanking transmission of airborne and impact
sound between adjoining rooms — Part 1: Frame document
ISO 15186-1:2000, Acoustics — Measurement of sound insulation in buildings and of building elements using
sound intensity — Part 1: Laboratory measurements
IEC 60721-2-2, Classification of environmental conditions — Part 2: Environmental conditions appearing in
nature — Precipitation and wind
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
© ISO 2006 – All rights reserved 1

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
IEC 61672-2:2003, Electroacoustics —Sound level meters — Part 2: Pattern evaluation tests
IEC 60942:2003, Electroacoustics — Sound calibrators
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
average sound pressure level in a room
L
ten times the common logarithm of the ratio of the space and time average of the squared sound pressure to
the square of the reference sound pressure, the space average being taken over the entire room with the
exception of those parts where the direct radiation of a sound source or the near field of the boundaries (walls,
etc.) is of significant influence
NOTE 1 The sound pressure level is given in decibels (dB).
NOTE 2 If a continuously moving microphone is used, L is determined by the following equation:
T
m
2
1/Tp (t) dt
m

0
L= 10 lg dB (1)
2
p
0
where
p(t) is the sound pressure, in pascals;
p is the reference sound pressure and is equal to 20 µPa;
0
T is the integration time, in seconds.
m
NOTE 3 If fixed microphone positions are used, L is determined by
22 2
pp++ .+p
12 n
L= 10 lg dB (2)
2
np
0
where p , p , …, p are r.m.s. sound pressures at n different positions in the room. In practice, usually the sound pressure
1 2 n
levels L are measured. In this case, L is determined by
i
n
1
L /10
i
L= 10 lg 10 dB (3)

n
i=1
where L are the sound pressure levels L to L at n different positions in the room.
i 1 n
3.2
sound intensity level
sound power level per unit area radiated by the test specimen into the test room below referenced to a value
−12 2
of 1 × 10 W/m
NOTE The sound intensity level is given in decibels (dB).
2 © ISO 2006 – All rights reserved

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
3.3
rainfall rate
depth of water layer created by spreading the rainfall on a horizontal surface in a 1 h time interval
NOTE The rainfall rate is given in millimetres per hour (mm/h).
3.4
volume median drop diameter
value when 50 % of the total volume of water sprayed is made up of drops with diameter larger than the
median value and 50 % with smaller diameter
NOTE The volume median drop diameter is expressed in millimetres.
4 Equipment
The accuracy of the sound level measurement equipment shall comply with the requirements of accuracy
classes 0 or 1 specified in IEC 61672-1:2002 and IEC 61672-2:2003. The complete sound measuring system
including the microphone shall be adjusted before each measurement using a sound calibrator which
complies with the requirements of accuracy class 1 specified in IEC 60942:2003.
The one-third-octave band filters shall comply with the requirements specified in IEC 61260.
The reverberation time measurement equipment shall comply with the requirements specified in ISO 3382-2.
5 Test arrangement
5.1 Test room
A test room without a permanent roof or with an opening in the roof for installation of the test specimens is
required for these measurements; however, if the intensity method is used, then the receiving space shall
meet the requirements given in 7.4.
The requirements of the test room are based on ISO 140-1. The volume of the test room shall be at least
3
50 m . The ratios of the room dimensions shall be so chosen that the natural frequencies in the low
frequencies are spaced as uniformly as possible. If necessary, diffusing elements should be installed in the
test room to obtain a diffuse field.
The airborne sound insulation of the walls, door(s) and floor of the test room shall be sufficiently high so that
the sound field measured in the test room is only that generated by the impact excitation of the test specimen
and radiated from the test specimen.
The background noise level in the test room shall be sufficiently low to permit the measurement of sound
generated by excitation of the test specimen with artificial rainfall. The correction associated with background
noise is discussed in 7.3.2.
The reverberation time in the test room should not be excessively long. It is recommended that the
reverberation time in the test room be not more than 2 s at low test frequencies. If the reverberation time in the
test room is too long, proceed according to ISO 140-1.
5.2 Test specimen
5.2.1 Standard specimen and laboratory configuration
2 2
The size of the opening shall be between 10 m and 20 m , with the length of the shorter edge being not less
than 2,3 m. The test specimen shall be well sealed at the perimeter with the test room to prevent leakage
sound transmission. The joints within the test specimen, if any, shall be sealed in a manner as similar as
possible to the actual construction.
© ISO 2006 – All rights reserved 3

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
For skylights, the preferred dimensions are 1 500 mm × 1 250 mm with limit deviations of ±50 mm. Skylights
shall be installed in a filler slab construction of sufficiently high airborne sound insulation and well sealed at
the perimeter so that the sound field measured in the test room is only that generated by the impact excitation
of the test specimen and radiated from the test specimen.
The minimum slope of the test specimen is 5° for roofs and 30° for skylights. The slope used shall be the
lowest that is feasible to assure water drainage. Unrepresentative niches should be limited as far as is
possible in practice for small test specimens like skylights, for example by installing the test specimen in a test
opening in a construction having the same slope as the slope of the test specimen.
The position of a small test opening in the surrounding roof construction shall fulfil the same specifications as
for a window opening in a test wall in accordance with ISO 140-3.
5.2.2 Other configurations
2
Specimens of surface area less than 1 m are not recommended. The slope of the test specimen may be the
actual slope for specific situations/systems, if known.
6 Classification of rain types
The real rain can be classified in terms of rainfall rate, typical drop diameters and fall velocities in accordance
with IEC 60721-2-2. These values are given in Table 1.
Table 1 — Classification of rain type according to IEC 60721-2-2
Rainfall rate Typical drop diameter Fall velocity
Rainfall type
mm/h mm m/s
Moderate up to 4 0,5 to 1,0 1 to 2
Intense up to 15 1 to 2 2 to 4
Heavy up to 40 2 to 5 5 to 7
Cloudburst greater than 100
> 3 > 6

7 Test equipment and procedure
This clause describes the artificial rainfall types for the measurements and generation systems for artificial
raindrops.
7.1 Rainfall type
7.1.1 Standard type
The standard rainfall type used for comparison between products shall be the heavy type; it should be noted
that the corresponding rainfall rate might be too high when applied to a real case with lighter rain. The
characteristic parameters of the artificial raindrops for this type of rainfall shall be chosen in accordance with
Table 2, line 2. These values are based on Table 1 and upper limits have been chosen since larger drops
produce most of the noise generated.
7.1.2 Other types
Other types of rainfall are permitted as long as their characteristics are indicated; however, if a rainfall rate
lower than the heavy rain is needed, then the intense type described in Table 2, line 1 is recommended.
4 © ISO 2006 – All rights reserved

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
Table 2 — Characteristic parameters for artificial raindrops generation
Rainfall rate Volume median drop diameter Fall velocity
Rainfall type
mm/h mm m/s
Intense 15 2,0 4,0
Heavy 40 5,0 7,0

Tolerances on the three characteristic parameters for artificial raindrops generation given in Table 2 are as
follows:
a) the rainfall rate shall be within ±2 mm/h of the rainfall rate given in Table 2;
b) 50 % of the drops should be within ±0,5 mm of the volume median drop diameter given in Table 2;
c) 50 % of the drops should be within ±1 m/s of the fall velocity given in Table 2.
7.2 Generation of artificial raindrops
7.2.1 General
The artificial raindrop generation system, when connected to a water supply, is capable of generating water
drops of uniform diameter in a full water spray pattern. The water supply to generate artificial raindrops may
be either a closed loop type or a continuous type that enables continuous generation of constant diameter
water drops over a long period of time.
After impacting on the test specimen, the water shall be drained to eliminate extraneous noise generation. The
water supply pump shall either be located well away from the test room, or shall be housed in an acoustic
enclosure so that its contribution to the background noise does not make rainfall measurements invalid. For
smaller test specimens such as skylights, a single position for the artificial raindrop generation system is
2 2
sufficient. For larger test specimens (10 m to 20 m , see 5.2.1), three positions for the artificial raindrop
generation system shall be chosen. The location of the impact of artificial raindrops on the test specimen
should be slightly off-centre to avoid symmetry. For non-uniform smaller test specimens (size close to
1,25 m × 1,5 m, see 5.2.1) the whole surface shall be excited.
7.2.2 Artificial raindrop generation system
The artificial raindrop system shall be a tank with a perforated base capable of generating water drops with
the specification given in Table 2 in a full spray pattern. The perforations on the tank base should be
2
distributed over a minimum area of 1,6 m , thus totally covering smaller test specimens in the standard
configuration with a 30° slope; a random distribution is preferred rather than a uniform distribution (see
Figure A.1).
The water supply pressure and the number of perforations shall be chosen so that the water height in the tank
is constant and allows the rainfall rate given in Table 2 to be generated by the perforated tank. The perforation
characteristics (diameter) of the tank base shall be chosen so that water drops with the volume median drop
diameter given in Table 2 are produced by the perforated tank. The fall height of the artificial raindrops shall
be adjusted such that either the measured or the theoretically calculated fall velocities based on perforation
dimensions, water pressure and fall height are as given in Table 2. For the determination of the fall height for
inclined surfaces, see Figure A.2. The specifications, dimensions and other design parameters of tanks with a
perforated base that meet the above requirements are given in Annex A, as well as a sketch showing a typical
test arrangement (see Figure A.2).
7.2.3 Calibration of the raindrop generation system
The artificial raindrop generation system shall be calibrated.
© ISO 2006 – All rights reserved 5

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SIST EN ISO 140-18:2007
ISO 140-18:2006(E)
If a water tank system is used and therefore follows the geometrical characteristics given in Annex A, then
only the rainfall rate shall be checked by collecting the water over a given area over a precisely measured
time period; the measurement of the rainfall rate allows a quick and simple method for periodic verification of
the artificial raindrop generation system.
If another system is selected in order to generate other types of rain fall, the rainfall type characteristics, i.e.
the drop size, drop velocity and rainfall rate, shall be given by the manufacturer; if they are not available, they
should be measured. Here again, the measurement of the rainfall rate allows a quick and simple method for
periodic verification of the artificial raindrop generation system.
NOTE There are several non-intrusive methods to measure drop size and drop velocity as, for example, imaging
analysers consisting of a light source (typically a strobe light), a video camera and a computer, or phase Doppler particle
analysers consisting of a transmitter, a receiver, a signal processor and a computer.
7.3 Determination of the sound intensity level (indirect method)
7.3.1 Sound pressure level measurements
Prior to the commencement of sound pressure level measurements, a steady artificial rainfall rate shall be
maintained over the test speci
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