ISO/TS 13471-2:2022

TECHNICAL ISO/TS
SPECIFICATION 13471-2
First edition
2022-08
Acoustics — Temperature influence on
tyre/road noise measurement —
Part 2:
Correction for temperature when
testing with the pass-by methods
Acoustique — Effet de la température sur les essais de bruit pneu/
route —
Partie 2: Correction de la température lors des essais utilisant les
méthodes au passage
Reference number
ISO/TS 13471-2:2022(E)
© ISO 2022

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ISO/TS 13471-2:2022(E)
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ISO/TS 13471-2:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
3.1 Acoustics . 1
3.2 Measured noise quantities . 2
3.3 Tyre and vehicle classes . 2
3.4 Road surface . 3
3.5 Temperatures. 3
4  Principles of the correction procedures . 4
5 Temperature measurement equipment . 5
6 Measurement methods . 5
6.1 General . 5
6.2 Measurement of air temperature . 5
6.3 Measurement of road surface temperature (optional) . 6
6.4 Measurement of tyre temperature (optional) . 6
7 Temperature range . 6
7.1 General . 6
7.2 Temperature range within which the correction procedure is valid . 6
8 Temperature correction procedure . 6
8.1 Correction to noise levels . 6
8.2 Temperature coefficient . 7
8.3 Spectral correction . 8
9 Compensation for the effect of power unit noise . 9
10 Measurement uncertainty assessment according to ISO/IEC Guide 98-3 .9
10.1 General . 9
10.2 Potential uncertainties . . 10
10.3 Uncertainty estimation of temperature correction . 10
10.4 Sources of uncertainty . 10
10.4.1 Temperature coefficients (γ ), δ . 10
t 1
10.4.2 Temperature measurements (T), δ . . 10
2
10.4.3 Road surface category (rs), δ . 11
3
10.4.4 Vehicle effect, δ . 11
4
10.4.5 Solar radiation and warming of tyres, δ . 11
5
10.4.6 Tyre effect, δ . 11
6
10.5 Estimation of uncertainties . 11
11 Test report .12
Annex A (informative) Information about road surface types .13
Annex B (informative) Selection of temperature for normalization .15
Bibliography .17
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ISO/TS 13471-2:2022(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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/
iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.
A list of all parts in the ISO/TS 13471 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/TS 13471-2:2022(E)
Introduction
Air, tyre and road surface temperatures affect noise emission from the tyre/road interaction, as
measured by means of, for example, the statistical pass-by (SPB) method specified in ISO 11819-1
or other pass-by methods. These methods allow the user to make measurements within a wide air
temperature range (5 °C to 35 °C) which means that temperature influence on the results may be
substantial.
Another common type of measurement where temperature effects on tyre/road noise are significant
is for noise tests on tyres most commonly conducted as pass-by on test tracks with a reference surface
[1]
according to ISO 10844 . This case is also considered in this document, with the aim to reduce the
uncertainties in such measurements. These are often made for legal purposes, such as type approval
or labelling of tyres or vehicles where tyres are the dominant noise source. This is further dealt with in
Annex A.
Temperature effects on noise depend on both the tyre and the road surface, the temperatures of
which are affected by ambient air temperature. The temperature has different effects on different
noise generation mechanisms and when also considering the effect of possible power unit noise mixed
with tyre/road noise, the temperature effect becomes even more complicated. Ideally, and whenever
possible, temperature corrections shall be tailored to not only the tested tyre/road combination as well
as to different tyre and vehicle categories, but also to the type of measurement method. For example,
[2]
there is also a Technical Specification related to the CPX method (ISO/TS 13471-1 ).
The approach to the temperature correction in this document is semi-generic, which means that under
certain conditions a correction to noise for temperature is made common to a group of vehicles and
tyres or a group of road surfaces as it is impossible to do it for each tyre and road surface combination.
This document makes a distinction to cars and heavy vehicles and to a few major road pavement
categories, and also takes into account local, regional or national conditions.
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TECHNICAL SPECIFICATION ISO/TS 13471-2:2022(E)
Acoustics — Temperature influence on tyre/road noise
measurement —
Part 2:
Correction for temperature when testing with the pass-by
methods
1 Scope
This document specifies correction procedures for the effect of temperature on vehicle noise emission,
as influenced by the tyre/road noise contribution. Temperatures considered are road and ambient air
temperatures.
The noise emission for which this document is applicable is measured by means of ISO 11819-1, or
similar methods such as the American methods SIP and CTIM specified in References [3][4]. It is also
applicable to other pass-by measurements conducted without acceleration, such as when testing tyres
[1]
and vehicles on test tracks with ISO 10844 reference surfaces; however, given that tyre/road noise is
dominant.
Measurement results obtained at a certain temperature, which may vary over a wide range, are
normalized to a designated reference temperature (20 °C) using a correction procedure specified in
this document.
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.
ISO 11819-1, Acoustics — Measurement of the influence of road surfaces on traffic noise — Part 1: The
statistical pass-by method
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: 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 terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Acoustics
3.1.1
vehicle noise
total noise from an individual vehicle, the two major components of which are power unit noise (3.1.3)
and tyre/road noise (3.1.2)
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ISO/TS 13471-2:2022(E)
3.1.2
tyre/road noise
noise generated by the tyre/road interaction
3.1.3
power unit noise
noise generated by the vehicle engine, exhaust system, air intake, fans, transmission, etc.
3.1.4
SPB method
statistical pass by method
measurement procedure designed to evaluate vehicle and traffic noise generated on different sections
of road surface under specific traffic conditions
Note 1 to entry: The measurements are taken from a great number of vehicles operating normally on the road.
Results obtained using this procedure are normalized to standard speeds according to the category or type of
road being considered. The method is specified in ISO 11819-1.
3.2 Measured noise quantities
3.2.1
maximum sound level
L
Amax
highest sound pressure level recorded by the measuring instrument during a vehicle pass-by, using
frequency weighting A and time weighting F
3.2.2
vehicle sound level
L
VEH: U ,vref
maximum A weighted sound pressure level determined at a reference speed, v , calculated for one of
ref
the universal vehicle categories (U) defined in 3.3.2
Note 1 to entry: When testing according to ISO 11819-1, L is equal to L
VEH,J,vref SPB,J,vref
3.2.3
tyre/road sound level
L
TR: C ,vref
maximum A weighted sound pressure level determined at a reference speed, v , measured or
ref
calculated in conditions where there is no power unit noise (coast-by passing or similar), for one of the
tyre classes (C) which can be C1, C2 or C3 defined in 3.3.1
3.3  Tyre and vehicle classes
3.3.1
tyre class
dimensional class of tyres
[5]
Note 1 to entry: Tyre classes C1, C2 and C3 are defined in ECE Regulation 117 .
Note 2 to entry: Essentially, C1 tyres are used on cars and other light vehicles, C2 tyres are used on large SUV:s,
vans and small trucks, while C3 tyres are used on heavy vehicles. However, refer to the reference [5] for more
precise definitions based on tyre load indices.
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ISO/TS 13471-2:2022(E)
3.3.2
vehicle category
universal category of vehicles (U), using a certain class of tyres, that can be either P (passenger cars
using C1 tyres), H (heavy vehicles using C3 tyres) or M (a medium category of vehicles using C2 tyres,
mostly consisting of large SUV:s, vans and small trucks)
1)
Note 1 to entry: Vehicle categories P and H are defined in ISO 11819-1:- , and tyre classes are defined in 3.3.1.
Vehicle category M is not used in ISO 11819-1.
3.4 Road surface
3.4.1
surface course
upper course of the pavement, which is in contact with the tyres
Note 1 to entry: Various main types of road surfaces are described in Annex A.
3.5 Temperatures
3.5.1
air temperature
ambient air temperature
temperature of the air surrounding the traffic flow
Note 1 to entry: The air temperature is expressed in degree Celsius.
Note 2 to entry: Instructions on where and how to measure air temperature are given in 6.2.
3.5.2
road temperature
road surface temperature
temperature representative of the temperature in the wheel tracks of the road surface
Note 1 to entry: The road temperature is expressed in degree Celsius.
Note 2 to entry: Instructions on where and how to measure road surface temperature are given in 6.3.
3.5.3
tyre temperature
general term for the temperature of the test tyres
Note 1 to entry: The tyre temperature is expressed in degree Celsius.
Note 2 to entry: Tyre temperature varies substantially between different parts of the tyre, as well as with the
tyre operating conditions. In this document, distinction is not made between these different parts, but the tyre is
seen as a unit with a temperature that influences noise emission in a particular way.
3.5.4
reference temperature
T
ref
air temperature (3.5.1) of 20,0 °C representing a hypothetical, ideal measurement case, to which actual
measurements are normalized
3.5.5
temperature correction term for tyre class t
C
T,t
term used for correcting the tyre/road sound level (3.2.3) for temperature T for tyre class t
Note 1 to entry: The temperature correction term is expressed in decibels.
1) A revision of ISO 11819-1 where the vehicle categories are defined is currently under preparation.
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ISO/TS 13471-2:2022(E)
3.5.6
temperature correction term for vehicle category
C
T,U
term used for correcting the vehicle sound level (3.2.2) for temperature T for vehicle category U
Note 1 to entry: The temperature correction term is expressed in decibels.
Note 2 to entry: This term represents how C is “diluted” by power unit noise of the particular vehicle category
T,t
(see Clause 9).
3.5.7
temperature coefficient
γ
t
coefficient used for correcting the tyre/road sound level (3.2.3), for the effect of temperature for tyre
class t
Note 1 to entry: The temperature coefficient is expressed in decibels per degree Celsius.
Note 2 to entry: Tyre t can be classes C1, C2 or C3 (3.3.1).
3.5.9
temperature coefficient
γ
U
coefficient used for correcting the vehicle sound level (3.2.2) for the effect of temperature for vehicle
category U
Note 1 to entry: The temperature coefficient is expressed in decibels per degree Celsius.
Note 2 to entry: Vehicle category U can be P, M or H (3.3.2).
Note 3 to entry: This coefficient is the version of γ taking into account how it is “diluted” by power unit noise of
t
the particular vehicle category (see Clause 9)
4  Principles of the correction procedures
The general effect of temperature is an increase in sound levels with colder temperatures and a
decrease in sound levels with warmer temperatures. Based on the empirically determined relationship
between tyre/road noise and ambient air temperature, the aim is to normalize all coast-by and pass-by
noise measurements (including, for example, SPB measurements) to a reference temperature. This is
done from the actual air temperature during the measurement, within a temperature range where the
relationship is reasonably linear.
The reference condition has been determined to be a hypothetical measurement of noise at an ambient
air temperature of 20,0 °C. The relationship between noise and temperature has been determined from
a compilation of several published investigations. It has been found that the relationship depends on the
class of tyres and types of road surfaces, and somewhat different relationships are, therefore, necessary
[6]
to apply based on the road surface type, and to some extent the condition of the surface (porosity) .
In this way, measured overall A-weighted levels as well as spectral levels, corrected for the difference
between actually measured temperature and the reference temperature using formulae given in this
document, are normalized to a common reference condition where air temperature would be 20 °C.
In general, it is advised that measurements be made as close as possible to the reference temperature,
in order to avoid large corrections. In cases when one wants to compare, for example, a before–after
measurement of some type, the lowest uncertainties will result if such before–after measurements are
made at similar temperatures; in particular, if temperatures during measurements are relatively far
from the reference temperature.
When using a semi-generic correction procedure, it is accepted that the use of an average temperature
coefficient for either tyre/road noise or vehicle noise considered in this document, with a distinction
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ISO/TS 13471-2:2022(E)
between a few major road pavement categories, will lead to some over- and under-estimations of
temperature corrections for individual tyres, vehicles or pavements. However, the errors of such
imperfect corrections are more than balanced by the correction itself as it normalizes the results to a
common and comparable scale.
This procedure will reduce the uncertainty in coast-by, SPB and other pass-by measurements due to
varying temperature substantially. An analysis of uncertainty is included in this document.
Refer to Annex B for a discussion about the choice of temperature to use for normalization.
5 Temperature measurement equipment
The air, road and tyre temperature measuring instrument(s) shall have a maximum permissible error
of ±1 °C, as specified by the manufacturer. Meters utilizing the infrared technique shall not be used for
air temperature measurements.
NOTE Obviously, the tyre temperature measurement option is impossible in SPB measurements.
The equipment shall be calibrated in accordance with the manufacturer’s specification, in most cases
requiring a calibration annually by a laboratory authorized to perform calibrations traceable to
appropriate standards.
The type of sensor used shall be reported.
6 Measurement methods
CAUTION — This document may involve hazardous operations when measurements are made
on trafficked roads or streets. The personnel and the vehicles present on the measuring site
shall be equipped with safety or warning devices in accordance with the regulations in force
for work in the traffic flow (if any) on that particular site at that particular time. Otherwise,
this document does not purport to address the safety problems associated with its use. It is the
responsibility of the user of this document to establish appropriate safety and health practices
and determine the applicability of regulatory limitations prior to use.
6.1  General
The measurements shall comprise at least the first of the following operations.
— Measurement of air temperature representative of the ambient air at the test site (mandatory).
— Measurement of road temperature representative of the road surface of the test site (optional).
— Measurement of tyre temperature (optional).
The thermometer manufacturer’s instructions shall be observed. The result is the reading rounded to
the first decimal, in °C.
NOTE Regarding the various temperatures considered, a discussion follows in 6.2 to 6.4. See also the
discussion in Annex B.
6.2 Measurement of air temperature
Locate the temperature sensor so that it is unobstructed and safe, and in such a way that it is protected
from direct solar radiation and heat radiation from road or other surfaces. The protection from solar
radiation may be achieved by a shading screen. Heights of 1,2 m to 1,5 m above road surface level are
suitable. The position of the sensor shall be reported.
The temperature measurement shall have a duration of at least 15 s of stable temperature.
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ISO/TS 13471-2:2022(E)
6.3  Measurement of road surface temperature (optional)
Position the temperature sensor in order to measure where the temperature is representative of the
temperature in the wheel tracks. Collect the measurements approximately simultaneously with the
noise measurement. Where portions of the roadway are in full sun and other portions are shaded it
is advised to collect and average the temperature values approximately over the same test section as
noise is collected.
The temperature measurement shall cover a few spots or a spot large enough to average out possible
differences between surface objects having different albedos.
NOTE 1 Surface temperatures can be different on bright exposed stones than on the much darker bitumen/
sand mortar between such stones.
NOTE 2 Regarding the problems with road surface temperatures, see the discussion in Annex B.
6.4  Measurement of tyre temperature (optional)
If one can control the test vehicle, tyre temperature measurements can be made either continuously
on-board the vehicle or immediately before or after the measurement. Position the temperature sensor
in order that it measures the tyre tread surface temperature. Where appropriate, in order to avoid dirt
thrown from the tyre by centrifugal forces, the sensor should not be positioned in the tyre plane but a
little outside the tyre plane. If tyre temperature is measured, the measuring position on the tyre shall
be reported.
NOTE Obviously, this option is impossible in SPB measurements.
7 Temperature range
7.1  General
In order to reduce the uncertainty, it is recommended that noise measurements be made at air
temperatures as close as practical to the reference air temperature (20,0 °C).
7.2  Temperature range within which the correction procedure is valid
The correction procedures in this document shall be applied only if air temperatures are within 5 °C
and 35 °C.
NOTE The allowed temperature range is related to local road materials. In the warmer zones, high
temperatures are common and bitumen viscosity is adjusted to it, while the same temperature in a cooler climate
can cause bleeding of the bituminous mixture. This is known to cause extra stick-snap sound from the rolling
tyre (see Reference [7], in particular chapter 12.1).
8 Temperature correction procedure
8.1  Correction to noise levels
Temperature correction shall be applied as follows. Each measured noise level, L , where
Amax
appropriately determined according to ISO 11819-1 shall be corrected by adding the term C , using
T,t
Formula (1):
CT=−γ ()−T (1)
Tt, t ref
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ISO/TS 13471-2:2022(E)
where
C is the noise level, L , correction for temperature (T) for tyre class (t), in dB, to be added to
T,t Amax
the measured noise level; t can also be represented by the vehicle category (U) in which the
particular tyre class is used, see Note 1;
γ is the temperature coefficient for tyre class t (either C1, C2, or C3), in dB/°C;
t
T is the air temperature (T) during the noise measurement, in °C;
T is the reference air temperature = 20,0 °C.
ref
The γ values are indicated in 8.2 below. However, to consider the potential effect of power unit noise, if
t
appropriate, one shall consider the weighting factors presented in Clause 9.
[8] [9]
For IS
...