ISO 13475-1:1999

Acoustics — Stationary audible warning devices used outdoors — Part 1: Field measurements for determination of sound emission quantities

This part of ISO 13475 specifies the test conditions by which the sound emission level of stationary audible warning devices can be obtained. The methods are applicable to sirens for use in public outdoor warning systems and sound signalling devices for use outdoors. The purpose of this test code is to be able to produce reliable sound emission level measurements for stationary sirens used for warning outdoors. This part of ISO 13475 does not cover spoken messages and contains no recommendations for specific warning signals.

Acoustique — Dispositifs d'alarme sonore fixes utilisés à l'extérieur — Partie 1: Mesurages sur le terrain des grandeurs d'émission acoustique

General Information

• Status: Published
• Publication Date: 03-Nov-1999
• ICS: 13.320 - Alarm and warning systems
• ICS: 17.140.20 - Noise emitted by machines and equipment
• Technical Committee: ISO/TC 43/SC 1 - Noise
• Drafting Committee: ISO/TC 43/SC 1 - Noise
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 17-Oct-2022

Relations

• Consolidated By: ISO 21549-5:2008 - Health informatics — Patient healthcard data — Part 5: Identification data
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 13475-1
First edition
1999-11-15
Acoustics — Stationary audible warning
devices used outdoors —
Part 1:
Field measurements for determination
of sound emission quantities
Acoustique — Dispositifs d'alarme sonore fixes utilisés à l'extérieur
Partie 1: Mesurages sur le terrain des grandeurs d'émission acoustique
A
Reference number
ISO 13475-1:1999(E)

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ISO 13475-1:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Test conditions .3
4.1 Test site .3
4.2 Mounting of apparatus .3
4.3 Instrumentation.3
4.4 Microphone positions .4
4.5 Measurement methods.4
4.6 Ambient conditions .8
4.7 Test procedure.8
5 Acoustic characteristics .8
5.1 Test signals .8
5.2 Duration of the measurement.9
5.3 Determination of the sound emission quantities .9
5.4 Measurement uncertainty .10
6 Information to be reported.10
Annex A (normative) Supply conditions.14
Annex B (normative) Calculation of combined expanded uncertainty.15
Bibliography.19
©  ISO 1999
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 • CH-1211 Genève 20 • Switzerland
Internet [e-mail]
Printed in Switzerland
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© ISO
ISO 13475-1:1999(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.
International Standard ISO 13475-1 was prepared by ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
ISO 13475 consists of the following parts, under the general title Acoustics — Stationary audible warning devices
used outdoors:
 Part 1: Field measurements for determination of sound emission quantities
 Part 2: Test room measurements
 Part 3: Outdoor propagation of warning signals over built-up areas
Annexes A and B form a normative part of this part of ISO 13475.
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© ISO
ISO 13475-1:1999(E)
Introduction
ISO 13475-1 describes field measurements. The test methods are intended to produce field test values of the sound
emission level of a siren as it is installed in an outdoor situation. These field test values may, together with the
stated measurement uncertainties, be used to check the specifications of delivered sirens or to compare the
performance of different sirens under the same conditions, emitting the same signals.
ISO 13475-2 describes precision measurements. This method is intended to produce a generally valid specification
of sirens for type tests, acceptance tests, or for use in the design of outdoor warning systems, etc.
In part 1 of ISO 13475, two types of field measurements are discussed. They are:
a) Flat-plate measurements: this method uses a microphone placed on a flat plate which is located on the
ground. During the measurement, the intended main sound radiation pattern of the warning devices is tilted
toward the microphone and plate assembly.
b) Horizontal measurements: this method is performed with the microphone placed at the same elevation as the
centre of the audible warning device (at a preferred height of 10 m).
Measurements made under optimal conditions in conformity with this part of ISO 13475 should result in standard
uncertainties equal to or less than the values given in Table 1. The standard uncertainty for actual measurement
conditions taking into account the cumulative effect of all causes of measurement uncertainty are treated in parts 1
and 2 of ISO 13475.
Table 1 — Uncertainty in determining immission-relevant C-weighted sound power levels
for stationary audible warning devices
Expected expanded
Reference Measurement method
uncertainty
Part 1: Field measurements Flat plate 2 dB
Horizontal 4 dB
Part 2: Precision measurements — 1 dB
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INTERNATIONAL STANDARD  © ISO ISO 13475-1:1999(E)
Acoustics — Stationary audible warning devices used outdoors —
Part 1:
Field measurements for determination of sound emission quantities
1 Scope
This part of ISO 13475 specifies the test conditions by which the sound emission level of stationary audible warning
devices can be obtained. The methods are applicable to sirens for use in public outdoor warning systems and
sound signalling devices for use outdoors.
The purpose of this test code is to be able to produce reliable sound emission level measurements for stationary
sirens used for warning outdoors.
This part of ISO 13475 does not cover spoken messages and contains no recommendations for specific warning
signals.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 13475. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 13475 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.
1)
IEC 60651 , Sound level meters.
1)
IEC 60804 , Integrating-averaging sound level meters.
IEC 60942, Sound calibrators.
IEC 61260, Octave-band and fractional-octave-band filters.
3 Terms and definitions
For the purposes of this part of ISO 13475, the following terms and definitions apply.
3.1
siren
audible warning device for use outdoors

1)
 These will be revised and combined as IEC 61672.
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ISO 13475-1:1999(E)
3.2
electronic siren
siren that produces tonal sounds by amplifying the output of an electronic signal generator and broadcasting the
amplified signal from one or more electrodynamic loudspeakers
NOTE Such sirens may also be used for giving voice messages.
3.3
electromechanical siren
siren that produces tonal sounds by flow interruptions generated in a rotating wheel
NOTE Electromechanical sirens are mechanical sirens driven by an electric motor.
3.4
pneumatic siren
siren that produces sound by periodically interrupting or modulating a flow of compressed air
NOTE The air compressor may be integral with or separate from the flow interrupter.
3.5
horizontally omnidirectional siren
siren that radiates sound approximately uniformly (within a specified tolerance) in all horizontal directions from the
siren at the specified frequency of the sound
3.6
directional siren
siren that radiates most of its sound in one or more specific directions
3.7
rotating or oscillating siren
directional siren that contains a mechanism which slowly rotates its beam of sound about a vertical axis
3.8
immission-relevant sound power level
L
W,imm
sound power level from a monopole source that would give the same sound pressure level in the far field as the
actual source
NOTE It is expressed in decibels (dB).
Table 2 — Symbols
Symbol Definition Unit
L Sound pressure level, ref. 20 mPa dB
p
L C-Weighted sound pressure level, ref. 20 mPa dB
pC
L Maximum C-weighted sound pressure level, measured with time weighting F dB
pCmax,F
according to 4.5.3
L Equivalent C-weighted sound pressure level over a time period T dB
pCeq,T
L Immission-relevant sound power level, ref. 1 pW dB
W,imm
L C-Weighted immission-relevant sound power level, ref. 1 pW dB
WC,imm
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4 Test conditions
4.1 Test site
The ground surface between the siren and the microphone shall be flat to within –1,0 m.
The surface between the warning device and the microphone may be covered with grass and/or pavement. There
shall be no sound-reflecting object (e.g. building walls or roofs) within the horizontal plane containing the base of the
sound source that are closer than twice the measurement distance from the source.
All structures within three times the measurement distance from both the source and the microphone shall be
described.
NOTE All surfaces near the sound source will reflect sound and, depending on their material, location, and orientation may
bias the results of the measurements. The intent of above specifications is to minimize the effects of all reflections except those
from the ground surface. The accuracy of the field measurements depend on distance, reflecting objects, reflections off the
ground, vertical directivity, near-field effects, and instrumentation. The contributions of uncertainty due to reflecting surface can
be calculated according to the procedure in annex B.
4.2 Mounting of apparatus
The warning sound source to be tested shall be located at or above the manufacturer's recommended installation
height above the ground; see Figures 1 and 5 and corresponding text.
The recommended height to the centre of the warning device (acoustic centre) according to this part of ISO 13475
is 10 m above the ground. The mounting should be carried out in accordance with this part of ISO 13475 or the
manufacturer's recommendations.
When the flat-plate measurement method is used (see 4.5), a tilt is recommended for sirens that are directional in
the vertical plane. The tilt shall be at such an angle that the normally vertical siren axis is perpendicular to the
direction to the microphone. If not tilted, the measured values shall be corrected using the vertical directional
characteristics (see annex B).
Power supply conditions shall be in accordance with annex A.
4.3 Instrumentation
4.3.1 Acoustical instruments
4.3.1.1 Equipment for determination of the sound pressure level
The sound level meter or the equivalent measuring system, including the windshield as recommended by the
manufacturer, shall fulfil the requirements of a class 1 or class 2 sound level meter according to IEC 60651 and
IEC 60804. The diameter of the microphone shall be less than or equal to 13 mm, when using the flat-plate method
(see 4.5.2).
4.3.1.2 Equipment for the optional determination of octave and one-third-octave-band spectra
The filters shall meet the requirements of IEC 61260, class 1 or class 2; parallel filters are preferred.
The equivalent continuous sound pressure levels shall be determined simultaneously in octave or one-third-octave
bands with centre frequencies from 50 Hz to 4 000 Hz.
4.3.1.3 Calibration of the measurement set-up
The calibration of the complete sound measuring system, including any recording, data logging, or r.m.s. computing
systems, shall be checked immediately before and after the measurement session at one or more frequencies using
a sound calibrator. The calibrator shall fulfil the requirements of IEC 60942, class 1 or class 2, and shall be used
within its specified environmental conditions.
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If a difference of 1,0 dB or more appears between subsequent calibration sessions, the instruments shall be
checked and the measurements shall be rejected.
4.3.1.4 Calibration of the equipment and its traceability
All equipment for sound measurements shall be checked regularly and shall be calibrated with traceability to
national standards. Calibration intervals for sound calibrators should be 12 months and for other equipment
24 months.
4.4 Microphone positions
Microphone positions are chosen in accordance with the measurement method.
Windshields shall be used during all measurements.
The reference distance between the siren centre and the microphone is 30 m. The maximum distance between the
siren and the microphone shall not exceed 50 m.
For optimizing the measurement distance, uncertainties arising from near-field effects and ground effects shall be
taken into consideration; see annex B.
4.5 Measurement methods
4.5.1 General
Two methods are described: the flat-plate method and the horizontal measurement method.
The flat-plate method requires the microphone to be placed on a flat plate on the ground. This method results in a
6 dB increase of the sound pressure level via the controlled reflection of the plate (relative to the free-field value).
However, in order to measure sound pressure levels of directive sirens, the main sound radiation pattern of the
siren shall be directed toward the flat plate.
The horizontal measurement method specifies that the microphone be mounted at the same elevation as the
warning device. This method results in a combined sound pressure measurement of both the direct sound path and
the reflected sound path.
4.5.2 Flat-plate method
The measurement set-up is sketched in Figures 1 to 4. The microphone shall be placed on the plate according to
Figure 1. The flat plate and the microphone position shall be in accordance with Figure 4. The microphone shall be
fixed to the plate according to Figures 2 or 3. The plate shall be painted white to avoid thermal effects.
The angle a between the line SM, see Figure 1, connecting the microphone and the siren and the horizontal plane
shall not be less than 10°.
Since this measurement method doubles the sound pressures relative to free-field measurements because of
reflections from the plate, 6 dB must be subtracted from the sound pressure level measured (L ) on the flat
p,meas
plate, according to 5.3.1.
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ISO 13475-1:1999(E)
Key
SM = 30 m
1  Siren
2  Microphone
3  Flat plate
Figure 1 — Flat-plate measurement set-up
Dimensions in millimetres
Key
1 Microphone
2 Steel wire of 3 mm diameter, e.g. 3 pieces
3 Windshield
4 Metal plate, 2,5 mm thick
Figure 2 — Inverted microphone location — Side view
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© ISO
ISO 13475-1:1999(E)
Key
1 Microphone
2 Windshield
3 Metal plate, 2,5 mm thick
NOTE Windshields are cut to purpose f
...