EN ISO 24504:2016

SLOVENSKI STANDARD
01-januar-2017
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Ergonomics - Accessible design - Sound pressure levels of spoken announcements for
products and public address systems (ISO 24504:2014)
Ergonomie - Barrierefreie Gestaltung - Schalldruckpegel gesprochener Ansagen für
Produkte und öffentliche Lautsprecheranlagen (ISO 24504:2014)
Ergonomie - Conception accessible - Niveaux de pression acoustique des annonces
vocales pour les produits et systèmes de sonorisation (ISO 24504:2014)
Ta slovenski standard je istoveten z: EN ISO 24504:2016
ICS:
13.180 Ergonomija Ergonomics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 24504
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2016
EUROPÄISCHE NORM
ICS 13.180
English Version
Ergonomics - Accessible design - Sound pressure levels of
spoken announcements for products and public address
systems (ISO 24504:2014)
Ergonomie - Conception accessible - Niveaux de Ergonomie - Barrierefreie Gestaltung -
pression acoustique des annonces vocales pour les Schalldruckpegel von gesprochenen Ansagen für
produits et systèmes de sonorisation (ISO Produkte und öffentliche Lautsprecheranlagen (ISO
24504:2014) 24504:2014)
This European Standard was approved by CEN on 27 May 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 24504:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 24504:2014 has been prepared by Technical Committee ISO/TC 159 “Ergonomics” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 24504:2016 by
Technical Committee CEN/TC 122 “Ergonomics” the secretariat of which is held by DIN.
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 December 2016, and conflicting national standards
shall be withdrawn at the latest by December 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 24504:2014 has been approved by CEN as EN ISO 24504:2016 without any modification.

INTERNATIONAL ISO
STANDARD 24504
First edition
2014-08-01
Ergonomics — Accessible design
— Sound pressure levels of spoken
announcements for products and
public address systems
Ergonomie — Conception accessible — Niveaux de pression
acoustique des annonces vocales pour les produits et systèmes de
sonorisation
Reference number
ISO 24504:2014(E)
©
ISO 2014
ISO 24504:2014(E)
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2014 – All rights reserved

ISO 24504:2014(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 Range of sound pressure level of spoken announcements . 4
5.1 General . 4
5.2 Criteria to determine the speech level. 5
5.3 Relevant factors related to speech perception . 5
5.4 A-weighted sound pressure level method to determine the speech level . 6
5.5 Simplified STI method to determine the minimum speech level . 7
Annex A (normative) Method for measuring the sound pressure level of spoken announcements
and ambient noise . 8
Annex B (informative) Effects of age-related hearing loss on word recognition .10
Annex C (informative) Examples of measurement condition and result records .16
Annex D (informative) STI method to determine minimum speech level .18
Bibliography .21
ISO 24504:2014(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 159, Ergonomics, Subcommittee SC 5, Ergonomics
of the physical environment.
iv © ISO 2014 – All rights reserved

ISO 24504:2014(E)
Introduction
Today, people conduct their daily lives along with spoken announcements from various products
such as home electrical appliances, information and telecommunication products, office-automation
equipment, heating equipment, toys, sanitary equipment, and health care products. Some products
use spoken announcements to provide instructions in indoor and outdoor public areas such as ticket
vending machines, elevators, and escalators. Public address systems are often installed to provide
spoken announcements. Such announcements can be indistinct to listeners because of hearing loss that
can occur with ageing or because of ambient noise in the surroundings.
This International Standard specifies methods for determining an appropriate sound level range of
spoken announcements so that all listeners, including people with age-related hearing loss, can hear
them properly against ambient noises. This sound level range specification was determined based on
results of experiments in which people of different ages participated. Spoken announcements for which
sound pressure levels are within the range specified in this International Standard are expected to be
audible and comfortably loud for most users in the presence of ambient noise.
This International Standard is intended to be applied as necessary to products depending on the
product type and its conditions of use. It does not apply to spoken announcements used for evacuation
or emergency purposes.
ISO 9921 specifies recommended levels of speech-communication quality necessary for conveying
comprehensive messages in different applications. Therefore, ISO 9921 differs from this International
Standard.
This International Standard adopts the principles of accessible design from ISO/IEC Guide 71, which are
amplified in ISO/TR 22411.
INTERNATIONAL STANDARD ISO 24504:2014(E)
Ergonomics — Accessible design — Sound pressure levels
of spoken announcements for products and public address
systems
1 Scope
This International Standard specifies methods to determine an appropriate sound pressure level range
for spoken announcements in environments where ambient noise is less than 80 dB. The specified
methods follow the concepts of ISO/IEC Guide 71 and includes consideration of older persons with
decreased hearing ability to determine sound pressure levels of spoken announcements. The spoken
speech levels that are specified in this International Standard are for products and public-address
systems. To improve the accessibility and usability of products, spoken announcements must not only
be audible but also presented at comfortable speech levels.
The target products that present spoken announcements are consumer products such as electronic home
appliances, information and communication technology services, and products providing services for
general users in public facilities indoors and outdoors such as train stations, airports, meeting rooms,
amusement parks, and fairs.
This International Standard is not applicable to products providing private information such as
automated teller machines in public spaces.
This International Standard is applicable when a loudspeaker producing a spoken announcement is
located a short distance from the user in an environment where the sound pressure level with a standard
frequency weighting A of ambient noise does not exceed 80 dB. This International Standard is applicable
to spoken announcements that are audible to persons with normal hearing for their age when presented
by a target product under quiet and anechoic conditions. This International Standard is applicable for
both recorded voice and synthetic speech announcements.
This International Standard does not specify sound pressure levels of spoken announcements for
systems with automatic sound pressure level control to compensate for fluctuating ambient noise levels.
This International Standard is not applicable to spoken announcements heard through headphones or
earphones, or to spoken announcements heard with the ear close to the speech sound source, such as
in ear speakers specified in IEC 60268-7. This International Standard considers only the audibility of
speech and not the process of speech understanding.
This International Standard does not specify the sound pressure levels of spoken announcements
presented in emergency situations such as signals for fire alarms, gas leakage, and crime prevention;
those are covered in ISO 7240-16 and ISO 7240-19. This International Standard does not specify the
sound pressure levels of spoken announcements in automobiles; those are covered in ISO 15006.
NOTE 1 A spoken announcement presented in a repetitive manner from a product such as electronic home
appliance is presumed to be heard as an auditory sign but not as a message and is therefore usable with a lower
sound pressure level of the spoken announcement than this International Standard specifies.
NOTE 2 It is known that the word recognition performance of native speakers of the language of the
announcement is better than that of non-native speakers.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 24504:2014(E)
ISO 389-1, Acoustics — Reference zero for the calibration of audiometric equipment — Part 1: Reference
equivalent threshold sound pressure levels for pure tones and supra-aural earphones
ISO 1996-1, Acoustics — Description, measurement and assessment of environmental noise — Part 1: Basic
quantities and assessment procedures
ISO 3382-2:2008, Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in
ordinary rooms
ISO 8253-1, Acoustics — Audiometric test methods — Part 1: Pure-tone air and bone conduction audiometry
IEC 60050-801, International Electrotechnical Vocabulary — Chapter 801: Acoustics and electroacoustics
IEC 60268-16, Sound system equipment — Part 16: Objective rating of speech intelligibility by speech
transmission index
IEC 61260, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-801, IEC 60268-16, and
the following apply.
3.1
spoken announcement
message presented by a live human voice, a synthesized voice, or a recorded/digitized human voice
3.2
ambient noise
sound other than the sound to be measured as a signal
Note 1 to entry: For this International Standard, spoken announcements are regarded as signals.
3.3
speech transmission channel
acoustic and/or electro-acoustic signal path between a source of a signal and a user
3.4
speech transmission index
STI
metric with values 0 through 1 representing the transmission quality of speech with respect to speech
intelligibility by a speech transmission channel
[SOURCE: IEC 60268-16]
3.5
simplified STI
metric with values 0 through 1 representing the transmission quality of speech with respect to speech
intelligibility by a speech transmission channel calculated only with octave-band sound pressure level
difference between the sound pressure level of spoken announcements and sound pressure level of
ambient noise based on STI specified in IEC 60286-16
Note 1 to entry: Simplified STI does not account for effects of reverberation.
3.6
speech level
sound pressure level with a standard frequency weighting A or octave-band equivalent sound pressure
level of a spoken announcement
2 © ISO 2014 – All rights reserved

ISO 24504:2014(E)
3.7
signal-to-noise ratio
S/N
sound pressure level of a signal measured relative to ambient noise
3.8
minimum speech level
speech level with a standard frequency weighting A at which a listener can achieve audibility
3.9
maximum speech level
speech level with a standard frequency weighting A at which half of the listeners feel that the spoken
announcement is too loud
3.10
audibility
extent to which the words of spoken announcements are recognizable by listeners
3.11
hearing threshold level
HTL
sound pressure level of a sound at which a person gives a predetermined percentage of correct detection
responses on repeated trials minus the reference equivalent threshold sound pressure level
Note 1 to entry: It applies to a specified signal and specified manner of signal presentation under specified
conditions according to ISO 8253-1. The reference equivalent threshold sound pressure level shall be in accordance
with ISO 389-1.
3.12
pure tone average
PTA
average in decibels of hearing threshold levels of specified frequencies
3.13
reverberation time
T
duration required for the space-averaged sound energy density in an enclosure to decrease by 60 dB
after the source emission has stopped
Note 1 to entry: The reverberation time is expressed in seconds.
ISO 24504:2014(E)
4 Symbols
Symbols used in this International Standard are presented below.
L sound pressure level of ambient noise with a standard frequency weighting A, in decibels, as
N,A
measured using the method specified in Annex A
L an octave-band sound pressure level of ambient noise in band i, in decibels, as measured using
N,i
the method specified in Annex A
L speech level with a standard frequency weighting A, in decibels, as measured using the method
S,A
specified in Annex A
L an octave-band sound pressure level of spoken announcements in band i, in decibels, as meas-
S,i
ured using the method specified in Annex A
T a transmission index of octave band i, presented as a metric rating between 0 and 1
i
I STI or simplified STI calculated as a weighted average of T from 125 Hz to 8 kHz octave bands
i
5 Range of sound pressure level of spoken announcements
5.1 General
This International Standard specifies the sound pressure level range of spoken announcements without
consideration of reverberation and distance between a signal source and a listener.
The range of the sound pressure level of spoken announcements shall be determined with a minimum
speech level and a maximum speech level. The minimum speech level for older users is higher than that
for young users, as presented in Annex B. The minimum speech level shall be set to maintain the audibility
of spoken announcements considering older listeners with otologically normal hearing for their age.
The maximum speech level shall be set to avoid annoyance of listeners with the spoken announcement.
Because of their greater hearing sensitivity in general, the speech level for younger adults is used to set
the limit used in this International Standard because they are expected to perceive discomfort at lower
levels than older adults.
[8]
Usually, a mean speech level is 55 dB to 75 dB at 1 m distance from a talker.
When a spoken announcement with a fixed sound pressure level is used, the level shall be adjusted to
fall between the minimum and the maximum speech levels, as calculated according to this International
Standard.
When the sound level is controllable by users, the level shall be variable to cover a part of the specified
range in this International Standard. Audible distortion of spoken announcement from a loudspeaker
should be avoided to choose the speech level range for a product.
NOTE It is useful to indicate a speech level range determined by this International Standard at or around the
volume control function using a device such as a volume knob, button, or slider.
The A-weighted sound pressure level method is the simplest method, but it has limitations. It shall not
be applied in the case of noises that are predominantly low-frequency noises or when ambient noise has
a dominant tonal component. In such cases, the effect of ambient noise will not be estimated correctly.
The simplified STI method, which is based on STI specified in IEC 60286-16, is applicable for broadband
noise both with and without dominant narrow band components. This method is more accurate than
the A-weighted sound pressure level method.
NOTE 1 Under circumstances in which the required conditions for both methods listed above cannot be
followed, the STI method described in Annex D according to IEC 60268–16 is useful.
4 © ISO 2014 – All rights reserved

ISO 24504:2014(E)
NOTE 2 To ascertain the appropriate sound pressure level range of spoken announcements for a product, the
level of noise that is typical in the operating environment of the product can be used.
5.2 Criteria to determine the speech level
The required speech level for comfortable listening to spoken announcement is 55 dB which minimizes
[9]
listening difficulty for younger adults in quiet conditions.
The required signal-to-noise ratio used to determine the minimum speech level for older adults can be
estimated using information provided in Annex B. Typical older listeners require a 5 dB signal-to-noise
ratio, which corresponds to an STI of 0,65, or better for the best understanding of a clearly spoken single
word in an anechoic condition under ambient noise. The difference of required S/N improvement for
older listeners from younger listeners is varied from 2 dB to 6 dB among languages. It depends on the
PTA difference between younger and older listeners.
The maximum speech level shall be determined by following 5.4. Younger adults have better hearing
sensitivity than older adults in general. Because they are expected to perceive discomfort at lower levels
than older adults, the level for younger adults is used to set the limit used in this International Standard.
5.3 Relevant factors related to speech perception
Sound reflections are expected to have a detrimental effect on speech perception. A method of STI in
IEC 60268-16, Annex L is the standardized method, by which one can predict the detrimental effect of
sound reflections. This method uses reverberation time, room volume of the space and distance between
a signal source, and a listener to predict STI. To adapt the criteria of STI 0,65 in a closed or a semi-closed
space, relevant factors shall be considered when the space is reverberant and/or the quality of a spoken
announcement is inferior.
Another factor is the effect of phonetic characteristics of speech for different languages. Annex B
presents results of variation of a word recognition test conducted in six countries. The difference of
mean scores between different languages for young listeners is approximately 5 dB.
For consumer products that present messages or instructions to users, users are assumed to be physically
near the product at the time the messages or instructions are presented. For the simulation method of
STI standardized in IEC 60268-16, Annex L, 2 m of distance between a signal source to the users will
meet the criteria 0,65 of STI under a typical reverberant environment when the signal-to-noise ratio is
5 dB to 10 dB.
Figure 1 presents the typical relation between the signal-to-noise ratio and STI with distance of 2,0 m.
At distances greater than 2 m, sound reflections might detrimentally affect speech transmission under
reverberant conditions.
This International Standard shall be used for distances equal to or less than 2 m between a signal source
and a listener. The record of measurement conditions and results shall be noted. Examples of the record
of measurement conditions and results are presented in Annex C.
NOTE 1 In a free field, where reverberation does not exist, the source-receiver distance is highly variable.
Reverberation need not be considered.
NOTE 2 The typical reverberation time of an elementary school classroom (dimensions: 8 m × 8 m × 3 m) is
0,45 s.
ISO 24504:2014(E)
1.0
A
0.9
B
0.8
0.7
C
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-10-50 5101520
Key
X S/N
Y STI
A anechoic space (T = 0,1 s)
B normal space (T=0,34 s)
C reverberant space (T=0,55 s)
Figure 1 — Relations between
...