EN 1793-6:2025

Road traffic noise reducing devices - Test method for determining the acoustic performance - Part 6: Intrinsic characteristics - Airborne sound insulation under direct sound field conditions

This document specifies a test method for measuring a quantity representative of the intrinsic characteristics of airborne sound insulation for road traffic noise reducing devices: the sound insulation index.
This document is applicable to:
-   determination of the intrinsic characteristics of airborne sound insulation of noise reducing devices to be installed along roads, to be measured either on typical installations alongside roads or in laboratory conditions;
-   determination of the intrinsic characteristics of airborne sound insulation of road traffic noise reducing devices in actual use;
-   comparison of design specifications with actual performance data after the completion of the construction work;
-   verification of the long-term performance of road traffic noise reducing devices (with a repeated application of the method);
-   interactive design process of new products, including the formulation of installation manuals.
This document does not apply to:
-   the determination of the intrinsic characteristics of airborne sound insulation of road traffic noise reducing devices to be installed in reverberant conditions, e.g. inside tunnels or deep trenches or under covers.
Results for the sound insulation index are expressed as a function of frequency in one-third octave bands, between 200 Hz and 5 kHz for qualification purposes. If it is not possible to get valid measurement results over the whole frequency range indicated, the results are given in a restricted frequency range and the reasons for the restriction(s) are clearly reported.
For indoor measurements, see Annex D.

Lärmschutzvorrichtungen an Straßen - Prüfverfahren zur Bestimmung der akustischen Eigenschaften - Teil 6: Produktspezifische Merkmale - Luftschalldämmung in gerichteten Schallfeldern

Dieses Dokument legt ein Prüfverfahren zur Messung einer Größe fest, die für die produktspezifischen Merkmale der Luftschalldämmung von Lärmschutzvorrichtungen an Straßen charakteristisch ist: den Schalldämmungsindex.
Dieses Dokument ist anwendbar für:
-   Bestimmung der produktspezifischen Merkmale der Luftschalldämmung von Lärmschutzvorrichtungen, die entlang von Straßen einzubauen sind und die entweder an typischen Anlagen entlang von Straßen oder unter Prüfstandbedingungen zu messen sind;
-   Bestimmung der produktspezifischen Merkmale der Luftschalldämmung von Lärmschutzvorrichtungen an Straßen im tatsächlichen Einsatz;
-   Vergleich der Bemessungsfestlegungen mit den tatsächlichen Leistungsdaten nach Abschluss der Bauarbeiten;
-   Überprüfung der Langzeitwirksamkeit von Lärmschutzvorrichtungen an Straßen (durch wiederholtes Anwenden des Verfahrens);
-   interaktiver Bemessungsprozess von neuen Produkten, einschließlich der Formulierung von Einbauanleitungen.
Dieses Dokument gilt nicht für:
-   die Bestimmung der produktspezifischen Eigenschaften der Luftschalldämmung von Lärmschutzvorrichtungen an Straßen, die in halligen Schallfeldern einzubauen sind, z. B. innerhalb von Tunneln, in ausgeprägten Tieflagen oder unter Abdeckungen.
Ergebnisse für den Schalldämmungsindex werden als Funktion der Frequenz in Terzbändern zwischen 200 Hz und 5 kHz zu Zwecken der Güteprüfung angegeben. Wenn es nicht möglich ist, gültige Messergebnisse über den gesamten angegebenen Frequenzbereich zu erzielen, werden die Ergebnisse in einem eingeschränkten Frequenzbereich angegeben und die Gründe für die Einschränkung(en) genau angegeben.
Hinsichtlich Messungen in Innenräumen siehe Anhang D.

Dispositifs de réduction du bruit du trafic routier - Méthode d'essai pour la détermination de la performance acoustique - Partie 6 : Caractéristiques intrinsèques - Isolation au bruit aérien dans des conditions de champ acoustique direct

Le présent document spécifie une méthode d'essai permettant de mesurer une grandeur représentative des caractéristiques intrinsèques de l'isolation aux bruits aériens des dispositifs de réduction du bruit du trafic routier: l'indice d'isolation acoustique.
Le présent document est applicable à:
-   la détermination des caractéristiques intrinsèques d'isolation aux bruits aériens de dispositifs de réduction du bruit destinés à être installés le long des routes, à mesurer sur des installations types le long des routes ou dans des conditions de laboratoire;
-   la détermination des caractéristiques intrinsèques d'isolation aux bruits aériens de dispositifs de réduction du bruit du trafic routier en service;
-   la comparaison des spécifications de conception avec des données de performance réelles de l'ouvrage de construction achevé;
-   la vérification des performances à long terme de dispositifs de réduction du bruit du trafic routier (par l'application répétée de la méthode);
-   un processus interactif de conception de nouveaux produits, y compris la formulation des manuels d'installation.
Le présent document ne s'applique pas à:
-   la détermination des caractéristiques intrinsèques d'isolation aux bruits aériens de dispositifs de réduction du bruit du trafic routier destinés à être installés dans des conditions réverbérantes, par exemple dans des tunnels, dans des tranchées profondes ou sous des couvertures.
Les résultats de l'indice d'isolation acoustique sont exprimés en fonction de la fréquence, par bandes de tiers d'octave allant de 200 Hz à 5 kHz, à des fins de qualification. S'il est impossible d'obtenir des résultats de mesure valables sur toute la plage de fréquences indiquée, les résultats sont donnés pour la plage de fréquences réduite et les raisons de la ou des restrictions sont clairement consignées.
Pour les mesures en intérieur, voir Annexe D.

Protihrupne ovire za cestni promet - Preskusna metoda za ugotavljanje akustičnih lastnosti - 6. del: Bistvene karakteristike - Izoliranost pred zvokom v zraku pri usmerjenem zvočnem polju

General Information

• Status: Not Published
• Publication Date: 23-Dec-2025
• ICS: 17.140.30 - Noise emitted by means of transport
• ICS: 93.080.30 - Road equipment and installations
• Technical Committee: CEN/TC 226 - Road equipment
• Drafting Committee: CEN/TC 226/WG 6 - Noise reducing devices
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Start Date: 17-Nov-2025
• Due Date: 21-Dec-2022
• Completion Date: 17-Nov-2025
• Ref Project: kSIST FprEN 1793-6:2025 - Road traffic noise reducing devices - Test method for determining the acoustic performance - Part 6: Intrinsic characteristics - Airborne sound insulation under direct sound field conditions

Relations

• Revises: EN 1793-6:2018+A1:2021 - Road traffic noise reducing devices - Test method for determining the acoustic performance - Part 6: Intrinsic characteristics - In situ values of airborne sound insulation under direct sound field conditions
• Effective Date: 18-Jan-2023
• Revised: EN 1793-6:2018 - Road traffic noise reducing devices - Test method for determining the acoustic performance - Part 6: Intrinsic characteristics - In situ values of airborne sound insulation under direct sound field conditions
• Effective Date: 04-Nov-2020

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 1793-6:2023
01-november-2023
Nadomešča:
SIST EN 1793-6:2018+A1:2021
Protihrupne ovire za cestni promet - Preskusna metoda za ugotavljanje akustičnih
lastnosti - 6. del: Bistvene karakteristike - Terenske vrednosti izolirnosti pred
zvokom v zraku pri usmerjenem zvočnem polju
Road traffic noise reducing devices - Test method for determining the acoustic
performance - Part 6: Intrinsic characteristics - In situ values of airborne sound insulation
under direct sound field conditions
Lärmschutzvorrichtungen an Straßen - Prüfverfahren zur Bestimmung der akustischen
Eigenschaften - Teil 6: Produktspezifische Merkmale - In-situ-Werte der
Luftschalldämmung in gerichteten Schallfeldern
Dispositifs de réduction du bruit du trafic routier - Méthode d'essai pour la détermination
de la performance acoustique - Partie 6 : Caractéristiques intrinsèques - Valeurs in situ
d'isolation aux bruits aériens dans des conditions de champ acoustique di
Ta slovenski standard je istoveten z: prEN 1793-6
ICS:
17.140.30 Emisija hrupa transportnih Noise emitted by means of
sredstev transport
93.080.30 Cestna oprema in pomožne Road equipment and
naprave installations
oSIST prEN 1793-6:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 1793-6:2023
oSIST prEN 1793-6:2023
CEN/TC 226
Date: 2023-03-31
prEN 1793-6:2023
Secretariat: AFNOR
Road traffic noise reducing devices — Test method for determining the
acoustic performance — Part 6: Intrinsic characteristics - Airborne sound
insulation under direct sound field conditions
Lärmschutzvorrichtungen an Straßen — Prüfverfahren zur Bestimmung der
akustischen Eigenschaften — Teil 6: Produktspezifische Merkmale —
Luftschalldämmung in gerichteten Schallfeldern
Dispositifs de réduction du bruit du trafic routier — Méthode d'essai pour la
détermination de la performance acoustique — Partie 6 : Caractéristiques
intrinsèques — Isolation au bruit aérien dans des conditions de champ acoustique
direct
CCMC will prepare and attach the official title page.

oSIST prEN 1793-6:2023
prEN 1793-6:2023(E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols and abbreviations . 13
5 Sound insulation index measurements . 15
5.1 General principle . 15
5.2 Measured quantity . 15
5.3 Test arrangement . 16
5.3.1 General. 16
5.3.2 Tests on purposely built full-size samples . 16
5.3.3 Tests on installed road traffic noise reducing devices . 16
5.3.4 Non-flat, inclined or curved road traffic noise reducing devices . 17
5.4 Measuring equipment . 23
5.4.1 Components of the measuring system . 23
5.4.2 Sound source . 23
5.4.3 Test signal . 23
5.5 Data processing . 24
5.5.1 Calibration . 24
5.5.2 Sample rate and filtering. 24
5.5.3 Background noise . 25
5.5.4 Scanning technique using nine microphones . 26
5.5.5 Adrienne temporal window . 26
5.5.6 Placement of the Adrienne temporal window . 28
5.5.7 Low-frequency limit . 29
5.6 Positioning of the measuring equipment . 30
5.6.1 Selection of the measurement positions . 30
5.6.2 Post measurements . 31
5.6.3 Additional measurements . 31
5.6.4 Reflecting objects . 31
5.6.5 Safety considerations . 31
5.7 Sample surface and meteorological conditions . 32
5.7.1 Condition of the sample surface . 32
5.7.2 Wind. 32
5.7.3 Air temperature. 32
5.8 Single-number rating . 32
5.8.1 General. 32
5.8.2 Acoustic elements . 32
5.8.3 Posts . 33
5.8.4 Global . 33
6 Measurement uncertainty . 34
7 Measuring procedure . 34
oSIST prEN 1793-6:2023
prEN 1793-6:2023 (E)
8 Test report . 35
Annex A (informative)  Low-frequency limit and window width . 37
Annex B (informative) Measurement uncertainty. 42
B.1 General . 42
B.2 Measurement uncertainty based upon reproducibility data . 42
B.3 Standard deviation of repeatability and reproducibility of the sound insulation
index . 42
Annex C (normative) Template of test report on airborne sound insulation of road traffic
noise reducing devices. 45
C.1 General . 45
C.2 Test setup (example) . 47
C.3 Test object and test situation (example) . 49
C.4 Results (example) . 51
C.4.1 Part 1 – Results for ‘element’ in tabular form . 51
C.4.2 Part 2 – Results for ‘element’ in graphic form . 52
C.4.3 Part 3 – Results for ‘post’ in tabular form . 53
C.4.4 Part 4 – Results for ‘post’ in graphic form . 54
C.4.5 Part 5 – Results for global condition (average of ‘element’ and ‘post’) in tabular form . 55
C.4.6 Part 6 – Results for global condition (average of ‘element’ and ‘post’) in graphic form . 56
C.5 Uncertainty (example) . 56
Annex D (informative) Indoor measurements for product qualification. 59
D.1 General . 59
D.2 Parasitic reflections . 59
D.3 Reverberation time of the room . 59
Bibliography . 60

oSIST prEN 1793-6:2023
prEN 1793-6:2023(E)
European foreword
This document (prEN 1793-6:2023) has been prepared by Technical Committee CEN/TC 226 “Road
equipment”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1793-6:2018+A1:2021.
EN 1793-6:2023 includes the following significant technical changes with respect to EN 1793-
6:2018+A1:2021:
— The definitions from 3.1 to 3.8 have been updated to be in accordance to the last version of EN
14388.
— The scanning technique is based on a nine-microphone grid; the use of a single microphone
displaced in nine positions has been abandoned.
— The formula to calculate the global single-number rating DL used in the previous version of
SI,G
this document has been changed.
— The use of categories of single-number rating is no longer permitted.
— One value for the standard deviation of reproducibility and repeatability in each one-third
octave frequency band has been retained, in place of three values (min, max and median) as
before (see Tables B.1 and B.2).
— The example in C.5 on the declaration of the measurement uncertainty has been updated
accordingly.
EN 1793-6:2023 is part of a series and should be read in conjunction with the following:
— EN 1793-1:2023, Road traffic noise reducing devices — Test method for determining the acoustic
performance — Part 1: Intrinsic characteristics — Sound absorption under diffuse sound field
conditions;
— EN 1793-2:2023, Road traffic noise reducing devices — Test method for determining the acoustic
performance — Part 2: Intrinsic characteristics — Airborne sound insulation under diffuse sound field
conditions;
— EN 1793 3:2023, Road traffic noise reducing devices — Test method for determining the acoustic
performance — Part 3: Normalized traffic noise spectrum;
— EN 1793-4:2023, Road traffic noise reducing devices — Test method for determining the acoustic
performance — Part 4: Intrinsic characteristics — Intrinsic sound diffraction;
— EN 1793-5:2023, Road traffic noise reducing devices — Test method for determining the acoustic
performance — Part 5: Intrinsic characteristics — Sound absorption under direct sound field
conditions;
oSIST prEN 1793-6:2023
prEN 1793-6:2023 (E)
Introduction
Noise reducing devices alongside roads should provide adequate sound insulation so that sound
transmitted through the device is not significant compared with the sound diffracted over the top. This
document specifies a test method for assessing the intrinsic airborne sound insulation performance for
noise reducing devices designed for roads in non-reverberant conditions. It can be applied indoors or
outdoors. Indoors, it can be applied in a purposely built test facilities, e.g., inside a laboratory. Outdoors,
it can be applied in a purposely built test facilities, e.g., near a laboratory or a factory, as well as in situ,
i.e., where the road traffic noise reducing devices are installed. The method can be applied without
damaging the surface of the road traffic noise reducing device.
The method can be used to qualify products to be installed along roads as well as to verify the
compliance of installed road traffic noise reducing devices to design specifications. Regular application
of the method can be used to verify the long-term performance of road traffic noise reducing devices.
The method requires the averaging of results of measurements taken at different points behind the
device under test. The method is able to investigate flat and non-flat products.
The method uses the same principles and equipment for measuring sound reflection (see
EN 1793-5:2023) and airborne sound insulation (the present document).
The measurement results of this method for airborne sound insulation are comparable but not identical
with the results of EN 1793-2:2023 method, mainly because the present method uses a directional
sound field, while EN 1793-2:2023 method assumes a diffuse sound field (where all angles of incidence
are equally probable). Research studies suggest that good correlation exists between laboratory data,
measured according to EN 1793-2:2023 and field data, measured according to the method described in
the present document [4-9].
The test method described in this Document should not be used to determine the intrinsic
characteristics of airborne sound insulation for road traffic noise reducing devices to be installed in
reverberant conditions, e.g., inside tunnels or deep trenches or under covers.
For the purpose of this document, reverberant conditions are defined based on the geometric envelope,
e, across the road formed by the barriers, trench sides or buildings (the envelope does not include the
road surface) as shown by the dashed lines in Figure 1. Conditions are defined as being reverberant
when the percentage of open space in the envelope is less than or equal to 25 %, i.e., reverberant
conditions occur when w/e ≤ 0,25, where e = (w+h +h ).
1 2
This document introduces a specific quantity, called sound insulation index, to define the airborne
sound insulation of a road traffic noise reducing device. This quantity should not be confused with the
sound reduction index used in building acoustics, sometimes also called transmission loss.
This method can be used to qualify noise reducing devices for other applications, e.g., to be installed
nearby industrial sites. In this case, the single-number ratings can preferably be calculated using an
appropriate spectrum.
oSIST prEN 1793-6:2023
prEN 1793-6:2023(E)
a) Partial cover on both sides of the road; b) Partial cover on one side of the road;
envelope, e = w+h +h envelope, e = w+h , h = 0
1 2 1 2
c) Deep trench; d) Tall barriers or buildings;
envelope, e = w+h +h envelope, e = w+h +h
1 2 1 2
Key
r road surface
w width of open space
h Developed length of element, e.g. cover, trench side, barrier or building
h Developed length of element, e.g. cover, trench side, barrier or building
NOTE Figure 1 is not to scale.
Figure 1 — Sketch of the reverberant condition check in four cases
oSIST prEN 1793-6:2023
prEN 1793-6:2023 (E)
1 Scope
This document describes a test method for measuring a quantity representative of the intrinsic
characteristics of airborne sound insulation for road traffic noise reducing devices: the sound insulation
index.
The test method is intended for the following applications:
— determination of the intrinsic characteristics of airborne sound insulation of noise reducing devices
to be installed along roads, to be measured either on typical installations alongside roads or or in
laboratory conditions;
— determination of the intrinsic characteristics of airborne sound insulation of road traffic noise
reducing devices in actual use;
— comparison of design specifications with actual performance data after the completion of the
construction work;
— verification of the long-term performance of road traffic noise reducing devices (with a repeated
application of the method);
— interactive design process of new products, including the formulation of installation manuals.
The test method is not intended for the determination of the intrinsic characteristics of airborne sound
insulation of road traffic noise reducing devices to be installed in reverberant conditions, e.g., inside
tunnels or deep trenches or under covers.
Results are expressed as a function of frequency in one-third octave bands, where possible, between
100 Hz and 5 kHz. If it is not possible to get valid measurement results over the whole frequency range
indicated, the results need to be given in a restricted frequency range and the reasons for the
restriction(s) need to be clearly reported.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
EN 1793-3:2023, Road traffic noise reducing devices - Test method for determining the acoustic
performance - Part 3: Normalized traffic noise spectrum
EN 14389:2023, Road traffic noise reducing devices - Procedures for determining long-term performance
EN 61672-1:2013, Electroacoustics — Sound level meters — Part 1: Specifications (IEC 61672-1)
ISO/IEC Guide 98-3:2008, Uncertainty of measurement —Guide to the expression of uncertainty in
measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
oSIST prEN 1793-6:2023
prEN 1793-6:2023(E)
— IEC Electropedia: available at https://www.electropedia.org/
3.1
road traffic noise reducing device
RTNRD
device designed to reduce the propagation of traffic noise away from the road environment
Note 1 to entry: An RTNRD can comprise acoustic elements (3.2) only or both structural (3.3) and acoustic
elements.
Note 2 to entry: Applications of RTNRDs include noise barriers (3.6), claddings (3.6), covers (3.7) and added
devices (3.8).
3.2
acoustic element
element whose primary function is to provide the acoustic performance of the device
3.3
structural element
element whose primary function is to support or hold in place the parts of the RTNRD
3.4
self-supporting acoustic element
acoustic element including its own structural element to support itself
3.5
noise barrier
road traffic noise reducing device which obstructs the direct transmission of airborne sound emanating
from road traffic
3.6
cladding
road traffic noise reducing device which is attached to a wall or other structure and reduces the amount
of sound reflected
3.7
cover
road traffic noise reducing device which either spans or overhangs the road
3.8
added device
additional component that influences the acoustic performance of the original road traffic noise
reducing device
Note 1 to entry: The added device is acting primarily on the diffracted energy.
3.9
sound insulation index
quantity representing the amount of sound transmitted through the device under test
Note 1 to entry: Formula (1) specifies how to calculate the sound insulation index
Note 2 to entry: The sound insulation index values in one-third octave bands are the result of a test according to
the present document
oSIST prEN 1793-6:2023
prEN 1793-6:2023 (E)
3.10
reference height
height h equal to half the height, h , of the road traffic noise reducing device under test: h = h /2
S B S B
Note 1 to entry: See Figures 2, 4, 6, 7 and 8
Note 2 to entry: When the height of the device under test is greater than 4 m and, for practical reasons, it is not
advisable to have a height of the source h = h /2, it is possible to have h = 2 m, accepting the corresponding low
S B S
frequency limitation (see 5.5.7).
3.11
source reference surface for sound insulation index measurements
ideal, smooth surface facing the sound source side of the road traffic noise reducing device under test
and just touching the most protruding and significant parts of it within the tested area
Note 1 to entry: The reference surface is as smooth as possible, and follows the inclination or curve of the device
under test within the tested area. For vertical and flat road traffic noise reducing devices, the reference surface is a
vertical plane. For inclined and flat road traffic noise reducing devices, the reference surface is a plane with the
same inclination. For curve and flat road traffic noise reducing devices, the reference surface is a curve surface
with the same curvature.
Note 2 to entry: See Figures 2, 7 and 8.
3.12
microphone reference surface
ideal, smooth surface facing the receiver side of the road traffic noise reducing device under test and
just touching the most protruding and significant parts of it within the tested area
Note 1 to entry: The reference surface is as smooth as possible, and follows the inclination or curve of the device
under test within the tested area. For vertical and flat road traffic noise reducing devices, the reference surface is a
vertical plane. For inclined and flat road traffic noise reducing devices, the reference surface is a plane with the
same inclination. For curve and flat road traffic noise reducing devices, the reference surface is a curve surface
with the same curvature.
Note 2 to entry: See Figures 2, 7 and 8.
3.13
source reference position
position facing the side to be exposed to noise when the device is in place, located at the reference
height h and placed so that its horizontal distance to the source reference surface is d = 1 m
S s
Note 1 to entry: See Figures 2, 4, 6, 7 and 8
Note 2 to entry: The actual dimensions of the loudspeaker used for the background research on which this
document is based are: 0,40 m x 0,285 m x 0,285 m (length x width x height).
oSIST prEN 1793-6:2023
prEN 1793-6:2023(E)
3.14
measurement grid for sound insulation index measurements
measurement grid constituted of nine equally spaced microphones in a 3x3 squared configuration
Note 1 to entry: The orthogonal spacing between two subsequent microphones, either vertically or horizontally,
is s = 0,40 m.
Note 2 to entry: See Figures 2, 3, 4, 6, 7, 8 and 4.5.4.
3.15
measurement grid reference position
position facing the receiver side of the device under test, located at the reference height h and placed
S
so that its horizontal distance to the microphone reference surface is d = 0,25 m
M
Note 1 to entry: See Figures 2, 6, 7 and 8
3.16
barrier thickness for sound insulation index measurements
distance t between the source reference surface and the microphone reference surface at a height
B
equal to the reference height h
S
Note 1 to entry: See Figures 2, 6, 7 and 8
3.17
free-field measurement for sound insulation index measurements
measurement taken with the loudspeaker and the microphone in an acoustic free field in order to avoid
reflections from any nearby object, including the ground, keeping the same geometry as when
measuring across the noise reducing device under test (see Figure 6)
3.18
Adrienne temporal window
Analysis window in the time domain to be used for the data processing
Note 1 to entry: Processing in accordance with this document
Note 1 to entry: The Adrienne temporal window is described in 5.5.5
3.19
background noise
noise coming from sources other than the source emitting the test signal
3.20
signal-to-noise ratio, S/N
difference in decibels between the level of the test signal and the level of the background noise at the
moment of detection of the test signal (within the Adrienne temporal window)
3.21
impulse response
time signal at the output of a system when a Dirac function is applied to the input
Note 1 to entry: The Dirac function, also called δ function, is the mathematical idealisation of a signal that is
infinitely short in time which carries a unit amount of energy.
oSIST prEN 1793-6:2023
prEN 1793-6:2023 (E)
Note 2 to entry: It is impossible in practice to create and radiate true Dirac delta functions. Short transient sounds
can offer close enough approximations but are not very repeatable. An alternative measurement technique,
generally more accurate, is to use a period of deterministic, flat-spectrum signal, like maximum-length sequence
(MLS) or exponential sine sweep (ESS), and transform the measured response back to an impulse response.

Key
1 road traffic noise reducing device height, 5 loudspeaker front panel
h [m]
B
2 source reference surface 6 distance between the loudspeaker front panel and source
reference surface, d [m]
S
3 microphone reference surface 7 microphone grid
4 reference height, h [m] 8 distance between the microphone grid and the microphone
s
reference surface [m]
Figure 2 — Sketch of the loudspeaker and the microphone grid close to the road traffic noise
reducing device under test for sound insulation index measurements (not to scale)

oSIST prEN 1793-6:2023
prEN 1793-6:2023(E)
Key
1 Road traffic noise reducing device height h [m] 3 Orthogonal spacing between two subsequent
B
microphones s [m
2 Reference height h [m]
S
Figure 3 — (not to scale) Measurement grid for sound insulation index measurements in front of
the device under test (receiver side); the yellow circles indicate the microphone positions,
labelled from M1 to M9
Key
1 loudspeaker front panel 5 Road traffic noise reducing device thickness t at height h
B S
[m]
2 measurement grid 6 horizontal distance microphone 5 - microphone reference
surface d at height h [m]
M S
3 reference height h [m] 7 Horizontal distance loudspeaker - microphone 5 d at
S T
height h [m]
4 horizontal distance loudspeaker -  S
source reference surface d at height h
S S
[m]
Note: 𝑑𝑑 =𝑑𝑑 +𝑡𝑡 +𝑑𝑑 ; see Formula (5).
𝑇𝑇 𝑆𝑆 𝐵𝐵 𝑀𝑀
Figure 4 — (not to scale) Sketch of the set-up for the reference “free-field” sound measurement
for the determination of the sound insulation index
oSIST prEN 1793-6:2023
prEN 1793-6:2023 (E)
4 Symbols and abbreviations
For the purposes of this document, the following symbols apply.
Table 1 – Symbols and abbreviations
Symbol or Designation Unit
abbreviation
a major axis of the ellipsoid of revolution used to define the maximum m
sampled area at oblique incidence
a , a , a , a Coefficient for the expression of the four-term full Blackman-Harris -
0 1 2 3
window
b Depth of the surface structure of the sample under test m
s
b Width of a portion of material of the sample under test m
m
c Speed of sound in air m/s
d Horizontal distance from the microphone reference surface to the m
M
measurement grid; it is equal to d = 0,25 m
M
d Horizontal distance from the front panel of the loudspeaker to the sound m
S
source reference surface; it is equal to: d = 1 m
S
d Horizontal distance from the front panel of the loudspeaker to the m
T
measurement grid; it is equal to: d + t + d
S B M
DL Single number rating of sound reflection dB
SI
δ Any input quantity to allow for uncertainty estimates -
i
Δf Width of the j-the one-third octave frequency band Hz
j
F Symbol of the Fourier transform -
f Frequency Hz
f Low frequency limit of sound reflection index measurements Hz
min
f Sample rate Hz
s
f cut-off frequency of the anti-aliasing filter Hz
co
h Noise reducing device height m
B
h Reference height m
S
h (t) Incident reference component of the free-field impulse response at the k- -
i,k
th measurement point
h (t) Transmitted component of the impulse response at the k-th measurement -
t,k
point
h (t) Background noise component of the impulse response at the k-th -
n,k
measurement point;
j Index of the j-th one-third octave frequency band (between 100 Hz and -
5 kHz, where possible)
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Symbol or Designation Unit
abbreviation
k Index of the k-th measurement point (k = 1 … n) -
k Coverage factor -
p
k Constant used for the anti-aliasing filter -
f
L Length of an acoustical element m
E
L Sample period length of a non-homogeneous noise reducing device m
p
n Number of measurement points on which to average (n = 9) -
r Radius of the maximum sampled area at normal incidence m
SI Sound transmission index in the j-th one-third octave frequency band -
j
s Orthogonal spacing between two subsequent microphones m
s Standard deviation of repeatability -
r
s Standard deviation of reproducibility -
R
S/N Signal to noise ratio dB
𝑠𝑠 Standard deviation of reproducibility of the single-number rating for -
𝑅𝑅,𝐷𝐷𝐷𝐷
𝑆𝑆𝑆𝑆,𝐸𝐸
“elements”
𝑠𝑠 Standard deviation of reproducibility of the single-number rating for -
𝑅𝑅,𝐷𝐷𝐷𝐷
𝑆𝑆𝑆𝑆,𝑃𝑃
“posts”
𝑠𝑠 Standard deviation of reproducibility of the single-number rating for -
𝑅𝑅,𝐷𝐷𝐷𝐷
𝑆𝑆𝑆𝑆,𝐺𝐺
“global”
S/N Signal-to-noise-ratio at the k-th microphone dB
k
S/N Signal-to-noise-ratio at the k-th microphone in the j-th one-third dB
j,k
frequency band
t Time s
t Thickness of the noise reducing device under test at the height h m
B S
t Air temperature °C
C
T Length of the Blackman-Harris trailing edge of the Adrienne temporal s
W,BH
window
T Total length of the Adrienne temporal window s
W,ADR
u Standard uncertainty -
U Expanded uncertainty -
w (t) Reference free-field component time window (Adrienne temporal -
i,k
window) at the k-th measurement point
w (t) Time window (Adrienne temporal window) for the reflected component -
r,k
at the k-th measurement point
oSIST prEN 1793-6:2023
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5 Sound insulation index measurements
5.1 General principle
The sound source emits a transient sound wave that travels toward the device under test and is partly
reflected, partly transmitted and partly diffracted by it. The microphone placed on the other side of the
device under test receives both the transmitted sound pressure wave travelling from the sound source
through the device under test, and the sound pressure wave diffracted by the top edge of the device
under test (for the test to be meaningful the diffraction from the lateral edges should be sufficiently
delayed). If the measurement is repeated without the device under test between the loudspeaker and
the microphone, the direct free-field wave can be acquired. The power spectra of the direct wave and
the transmitted wave give the basis for calculating the sound insulation index.
The sound insulation index shall be the logarithmic average of the values measured at nine points
placed on the measurement grid (scanning points). See Figure 3 and Formula (1).
The measurement shall take place in a sound field free from reflections within the Adrienne temporal
window. For this reason, the acquisition of an impulse response having peaks as sharp as possible is
recommended: in this way, the reflections coming from other surfaces can be identified from their delay
time and rejected.
5.2 Measured quantity
The expression used to compute the sound insulation index SI as a function of frequency, in one-third
octave bands, is:
( ) ( )
∫ �𝐹𝐹�ℎ 𝑡𝑡𝑤𝑤 𝑡𝑡�� 𝑑𝑑𝑑𝑑
𝑡𝑡,𝑘𝑘 𝑡𝑡𝑘𝑘
𝛥𝛥𝑓𝑓
𝑗𝑗
𝑛𝑛
∑
𝑆𝑆𝐼𝐼 =−10⋅𝑙𝑙𝑙𝑙� � (1)
𝑗𝑗 𝑘𝑘=1 2
𝑛𝑛
∫ �𝐹𝐹�ℎ (𝑡𝑡)𝑤𝑤 (𝑡𝑡)�� 𝑑𝑑𝑑𝑑
𝑖𝑖,𝑘𝑘 𝑖𝑖𝑘𝑘
𝛥𝛥𝑓𝑓
𝑗𝑗
where
h (t) is the incident reference component of the free-field impulse response at the k
i,k th
scanning point;
th
h (t)
is the transmitted component of the impulse response at the k scanning point;
t,k
w (t) is the time window (Adrienne temporal window) for the incident reference component
i,k
th
of the free-field impulse response at the k scanning point;
w (t) is the time window (Adrienne temporal window) for the transmitted component at the
t,k
th
k scanning point;
F is the symbol of the Fourier transform;
th
j
is the index of the j one-third octave frequency band (between 100 Hz and 5 kHz,
where possible);
Δf is the width of the jth one-third octave frequency band;
i
n = 9 is the number of scanning points.
oSIST prEN 1793-6:2023
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5.3 Test arrangement
5.3.1 General
The test method can be applied either on road traffic noise reducing devices installed alongside roads
or on real-size samples purposely assembled to be tested (indoors or outdoors) using the method
described here.
5.3.2 Tests on purposely built full-size samples
For applications on full-size samples purposely built to be tested using the method described here, e.g.
in an outdoor test facility, the specimen shall be built as follows (see Figure 5):
— a part, composed of acoustic elements, that extends at least 4 m and is at least 4 m high;
— a post 4 m high (if applicable for the specific noise reducing device under test).
— a part, composed of acoustic elements, that extends at least 2 m and is at least 4 m high;
The test specimen shall be mounted and assembled in the same manner as the manufactured device is
used in practice with the same connections and seals between components parts.
The tested area is a circle having a radius of 2 m centred on the middle of the measurement grid. The
sample shall be built large enough to completely include this circle for each measurement.
For qualifying the sound insulation index across posts only, it is only necessary to have acoustic
elements that extend 2 m or more on either side of the post (see Figure 5).
If the device under test has a post-to-post distance less than 4 m, the distance between posts should be
reduced accordingly but the overall minimum width of the construction should be the same as shown in
Figure 5.
5.3.3 Tests on installed road traffic noise reducing devices
For applications on noise reducing devices that are already installed along roads, the test specimen
shall be constructed as follows:
— for installed noise reducing devices using single acoustic elements to achieve full height:
• the test specimen shall be constructed as a single element which is representative of the
specific application;
• where the test specimen cannot be constructed as a single element or where the installed
road traffic noise reducing device is lower than 4 m, the test specimen shall be centred on
the loudspeaker axis (at reference height h = 2 m above the ground) and built up to 4 m
S
high using smaller height acoustic elements at the base and top as appropriate;
— for installed road traffic noise reducing devices using stacked elements to achieve full height:
• the test specimen shall be constructed as used in the specific application.
For applications on road traffic noise reducing devices that are already installed along roads, if there is
a plinth under the road traffic noise reducing device, it shall be considered part of the “sample under
test”.
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5.3.4 Non-flat, inclined or curved road traffic noise reducing devices
For flat or curved, vertical or inclined road traffic noise reducing devices, Figures 7 and 8 apply. For
cases not covered by these figures, measurements should be carried out in accordance with the
following general principles:
— the plane of the microphone grid is parallel to the microphone reference surface;
— the axis loudspeaker-microphone 5 is is horizontal and directed toward the sound source reference
surface;
— microphone 5 is as close as possible to the mid-height of the screen;
— the shortest distance of microphone 5 to the microphone reference surface is d = 0,25 m.
M
Road traffic noise reducing devices consisting of a horizontal or vertical juxtaposition of several distinct
types of screens (composition of shapes or structures of very large dimensions) must be characterised
in detail: each shape or structure must be specifically characterised under the conditions described in
this document.
For structures that do not allow the unequivocal application of these rules, measurements may be
carried out in strict compliance with the provisions of this Document. The responsibility for adapting
the method is left to the operator. A clear justification of all choices made shall be included in the test
report. However, the results obtained under these conditions may in no case be used for the declaration
of performance.
oSIST prEN 1793-6:2023
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(a) Sound insulation index measurements across (b) Sound insulation index measurements
elements and posts across a post only

(c) Sound insulation index measurements in front of a sample having a post-to-post distance
smaller than 4 m
Key
Thin circles: tested area for elements
Dotted circles: tested area for posts
L actual horizontal length of the acoustic elements having a post-to-post distance smaller than 4 m
L minimal horizontal length of the sample if the post-to-post distance is smaller than 4 m
tot
Figure 5 — Sketch of the minimum dimensions of full-size samples purposely built for testing
oSIST prEN 1793-6:2023
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Key
1 road traffic noise reducing device thickness, t [m] 2 loudspeaker
B
3 loudspeaker front panel 4 barrier height, h [m]
B
5 reference height, h [m] 6 horizontal distance loudspeaker – source reference
S
surface, d [m]
S
7 measurement grid 8 reference height, h [m]
S
9 horizontal distance microphone n. 5 –reference 10 horizontal distance loudspeaker – measurement
surface, d [m] grid, d [m]
M T
NOTE d= dt+ + d ; see Formula (5).
T SB M
Figure 6 — Sketch of the set-up for the sound insulation index measurement on a flat road traffic
noise reducing device (side view, not to scale)

oSIST prEN 1793-6:2023
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(a) across an inclined flat road traffic noise reducing device

(b) across an inclined non-flat road traffic noise reducing device
Key
1 source reference surface 2 reference height, h [m]
S
3 loudspeaker front panel 4 distance between the loudspeaker front panel and the
source reference surface, d [m]
S
5 microphone reference surface 6 microphone grid
7 distance between the 8 road traffic noise reducing device height, h [m]
B
measurement grid and the
reference surface, d [m]
M
Figure 7 — (not to scale) Sketches of the set-up for the sound insulation index measurement on
inclined road traffic noise reducing devices (side view)
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(a) Transmitted component measurements in front of a concave road traffic noise reducing
device
(b) Transmitted component measurements in front of a convex road traffic noise reducing
device
Key
1 source reference surface 2 reference height, h [m]
S
3 loudspeaker front panel 4 distance between the loudspeaker front panel and the
source reference surface, d [m]
S
5 microphone reference surface 6 microphone grid
7 distance between the measurement grid 8 road traffic noise reducing device height, h [m]
B
and the reference surface, d [m]
M
NOTE d= dt+ + d ; see Formula (5).
T SB M
Figure 8 — (not to scale) Sketches of the set-up for the sound insulation index measurement on
curve road traffic noise reducing devices (side view)
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Figure 9 — Sketch representing the essential components of the measuring system
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5.4 Measuring equipment
5.4.1 Components of the measuring system
The measuring equipment shall comprise an electro-acoustic system, consisting of an electrical signal
generator, a power amplifier and a loudspeaker, a microphone with its microphone amplifier and a
signal analyser capable of performing transformations between the time domain and the frequency
domain.
NOTE 1 Some of these componen
...