ISO/TR 17534-4:2020

TECHNICAL ISO/TR
REPORT 17534-4
First edition
2020-11
Acoustics — Software for the
calculation of sound outdoors —
Part 4:
Recommendations for a quality
assured implementation of the
COMMISSION DIRECTIVE (EU)
2015/996 in software according to
ISO 17534-1
Acoustique — Logiciels de prévision de bruit dans l'environnement —
Partie 4: Recommandations pour l'assurance qualité de la mise
en œuvre de la DIRECTIVE (UE) 2015/996 de la COMMISSION
EUROPÉENNE dans les logiciels selon l'ISO 17534-1
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Identification of the official documentation . 1
5 Uniform and agreed interpretation of ambiguities. 2
5.1 General . 2
5.2 Sloping objects . 2
5.3 Equivalent heights . 2
5.4 Alternative statistical approach . 3
5.5 Octave band centre frequency f .
m 3
5.6 Ground factor of the source area, G .
S 3
5.7 Distances in Figure 2.5.b of CNOSSOS-EU: 2015 . 3
5.8 Equivalent heights in Equation (2.5.20) of CNOSSOS-EU: 2015 . 3
5.9 Rayleigh’s Criterion . 4
5.10 Parameter e .4
5.11 Diffraction under favourable conditions . 4
5.12 Error in Figure 2.5.f and Equation (2.5.29) of CNOSSOS-EU: 2015 . 5
5.13 Lateral diffraction . 5
5.14 Reflection on nearly vertical objects . 6
5.15 Retrodiffraction . 6
6 Test cases . 7
6.1 General . 7
6.2 Test cases with intermediate and final results . 8
6.2.1 TC01-TC03 — Flat ground with homogeneous acoustic properties . 8
6.2.2 TC01 — Reflecting ground (G = 0). 8
6.2.3 TC02 — Mixed ground (G = 0,5) . 9
6.2.4 TC03 — Porous ground (G = 1) .10
6.2.5 TC04 — Flat ground with spatially varying acoustic properties .10
6.2.6 TC05 — Ground with spatially varying heights and acoustic properties .12
6.2.7 TC06 — Reduced receiver height to include diffraction in some frequency
bands .14
6.2.8 TC07 — Flat ground with spatially varying acoustic properties and long
barrier .17
6.2.9 TC08 — Flat ground with spatially varying acoustic properties and short
barrier .20
6.2.10 TC09 — Ground with spatially varying heights and and acoustic
properties and short barrier .24
6.2.11 TC10 — Flat ground with homogeneous acoustic properties and cubic
building — Receiver at low height .30
6.2.12 TC11 — Flat ground with homogeneous acoustic properties and cubic
object – receiver at large height .33
6.2.13 TC12 — Flat ground with homogeneous acoustic properties and
polygonal object — Receiver at low height .38
6.2.14 TC13 — Ground with spatially varying heights and acoustic properties
and polygonal object . .42
6.2.15 TC14 — Flat ground with homogeneous acoustic properties and
polygonal object — Receiver at large height .47
6.2.16 TC15 — Flat ground with homogeneous acoustic properties and four buildings 53
6.2.17 TC16 — Reflecting barrier on ground with spatially varying heights and
acoustic properties .57
6.2.18 TC17 — Reflecting barrier on ground with spatially varying heights and
acoustic properties — Reduced receiver height.62
6.2.19 TC18 — Screening and reflecting barrier on ground with spatially varying
heights and acoustic properties . .66
6.2.20 TC19 — Complex object and 2 barriers on ground with spatially varying
heights and acoustic properties . .70
6.2.21 TC20 — Ground with spatially varying heights and acoustic properties .76
6.2.22 TC21 — Building on ground with spatially varying heights and acoustic
properties.78
6.2.23 TC22 — Building with receiver backside on ground with spatially varying
heights and acoustic properties . .84
6.2.24 TC23 — Two buildings behind an earth-berm on flat ground with
homogeneous acoustic properties .89
6.2.25 TC24 — Two buildings behind an earth-berm on flat ground with
homogeneous acoustic properties – receiver position modified .94
6.2.26 TC25 — Replacement of the earth-berm by a barrier .100
6.2.27 TC26 — Road source with influence of retrodiffraction .106
6.2.28 TC27 — Source located in flat cut with retro-diffraction .109
6.2.29 TC28 — Propagation over a large distance with many buildings between
source and receiver .114
6.3 Summary of the final results .121
7 Example of a template form for the declaration of conformity .122
Bibliography .124
iv © ISO 2020 – All rights reserved

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
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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.
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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 17534 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.
Introduction
The structure of the ISO 17534 series is shown in Figure 1. ISO 17534-1 describes the general approach
of the ISO 17534 series, aiming to facilitate a standardized interpretation and a verifiably consistent
software implementation of outdoor sound calculation methods. ISO/TR 17534-2 contains general
recommendations for test cases and for a quality assurance interface. Further parts of the ISO 17534
series each address a specific outdoor sound calculation method for which they provide an agreed
interpretation of ambiguous aspects, a set of illustrative test cases along with reference solutions, and
an example of a template form for the declaration of conformity for software developers.
This document addresses the calculation method laid down in the COMMISSION DIRECTIVE (EU)
2015/996, hereafter referred to as CNOSSOS -EU: 2015.
The European Commission developed Common NOise aSSessment methOdS (CNOSSOS-EU) for road,
railway, aircraft and industrial noise for the purpose of strategic noise mapping. CNOSSOS-EU aims at
improving the consistency and comparability of noise assessment results across the EU Member States
which are performed on the basis of the data becoming available through the consecutive rounds of
strategic noise mapping in Europe.
Figure 1 — Structure of the ISO 17534 series
vi © ISO 2020 – All rights reserved

TECHNICAL REPORT ISO/TR 17534-4:2020(E)
Acoustics — Software for the calculation of sound
outdoors —
Part 4:
Recommendations for a quality assured implementation
of the COMMISSION DIRECTIVE (EU) 2015/996 in software
according to ISO 17534-1
1 Scope
This document facilitates a standardized interpretation and a verifiably consistent software
implementation of the sound propagation part of the calculation method CNOSSOS -EU: 2015 according to
ISO 17534-1. Other parts of CNOSSOS -EU: 2015, such as the source models or the calculation method for
aircraft noise, are beyond the scope of this document. This document provides an agreed interpretation
of ambiguous aspects of the sound propagation part of CNOSSOS -EU: 2015, a set of illustrative test cases
along with reference solutions, and an example of a template form for the declaration of conformity for
software manufacturers.
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 17534-1, Acoustics — Software for the calculation of sound outdoors — Part 1: Quality requirements
and quality assurance
ISO/TR 17534-2, Acoustics — Software for the calculation of sound outdoors — Part 2: General
recommendations for test cases and quality assurance interface
COMMISSION DIRECTIVE (EU) 2015/996 of 19 May 2015 establishing common noise assessment
methods according to Directive 2002/49/EC of the European Parliament and of the Council, Official
Journal of the European Union, L 168/1
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CNOSSOS -EU: 2015, ISO 17534-1,
and ISO/TR 17534-2 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 http:// www .electropedia .org/
4 Identification of the official documentation
COMMISSION DIRECTIVE (EU) 2015/996 of 19 May 2015 establishing common noise assessment
methods according to Directive 2002/49/EC of the European Parliament and of the Council, Official
Journal of the European Union, L 168/1, herein referred to as CNOSSOS -EU: 2015.
In its Chapter 2.5, “Calculation of noise propagation for road, railway, industrial sources”, CNOSSOS -EU:
2015 describes a method for calculating the attenuation of sound during propagation outdoors in order
to predict the levels of environmental noise at a distance from a variety of sources.
5 Uniform and agreed interpretation of ambiguities
5.1 General
The propagation of sound outdoors in CNOSSOS -EU: 2015 is calculated with a ray-based energetic model.
Attenuations are calculated in eight octave bands, and separately for two idealized meteorological
conditions labelled homogeneous and favourable. Finally, the A-weighted exposure level at a receiver
position is given as the weighted energetic sum over all sources, paths, meteorological conditions, and
octave bands.
Some aspects of the sound propagation model of CNOSSOS -EU: 2015 are not described in sufficient detail
to be unambiguous; in other aspects, in some part the official documentation is misleading. For each of
these problematic topics, an agreed interpretation is given in 5.2 to 5.15 to allow for a standardized
u nder s t a nd i n g of C NOS S OS -E U: 2015 .
The abbreviations are not explained when they are identical to those described in CNOSSOS -EU: 2015.
Symbols are not defined when they are identical to those applied in CNOSSOS -EU: 2015.
5.2 Sloping objects
Topic: CNOSSOS -EU: 2015 states in subclause 2.5.1 that “obstacles sloping, when modelled, more than
15° in relation to the vertical are out of the scope of this calculation method”. This restriction does not
constitute a general restriction of the method. Rather, it applies only to reflectors: obstacles sloping
more than 15° in relation to the vertical are not considered as reflectors.
Agreed interpretation:
Objects sloping more than 15° in relation to the vertical are not considered as reflectors, but are taken
into account in all other aspects of propagation such as ground effects and diffraction.
5.3 Equivalent heights
Topic: CNOSSOS -EU: 2015 states in subclause 2.5.3, under the headline "Significant heights above the
ground", that “If the equivalent height of a point becomes negative, i.e. if the point is located below
the mean ground plane, a null height is retained, and the equivalent point is then identical with its
possible image.” For points located below the mean ground plane, the equivalent height is set to zero in
the calculation of A . For the calculation of path length differences, it is irrelevant whether points
ground
lie above or below a mean ground plane, no points are shifted. For the calculation of Δ and
ground(S,O)
Δ special care has to be taken in the case that one of the respective end points lies below the
ground(O,R)
mean ground plane.
Agreed interpretation:
The first major step in the algorithm is to decide whether A or A must be calculated. The step
ground dif
is based on real coordinates, not equivalent heights. If a point lies below the mean ground plane, its
equivalent height is set to zero in the calculation of A . Equations (2.5.31) and (2.5.32) of CNOSSOS
ground
-EU: 2015 apply only in the most common case that both S and R lay above the mean ground plane. If
either S or R lies below the mean ground plane, the following simplified Equations apply:
Δ = A (CNOSSOS -EU: 2015, 2.5.31)
ground(S,O) ground(S,O)
Δ = A (CNOSSOS -EU: 2015, 2.5.32)
ground(O,R) ground(O,R)
2 © ISO 2020 – All rights reserved

For the calculation of path length differences, the original coordinates are used and no points are
shifted, i.e. in the calculation of Δ the original heights of S and R are used.
dif(S,R)
5.4 Alternative statistical approach
Topic: CNOSSOS -EU: 2015 mentions in subclause 2.5.5, under the headline "Statistical approach inside
urban areas for a path (S, R)", a statistical approach for calculations inside urban areas beyond the
first line of buildings. This approach is not described in sufficient detail to be subjected to the quality
assurance methodology of ISO 17534-1.
Agreed interpretation:
A statistical approach is not appropriate in the calculation of sound propagation beyond the first line of
buildings.
5.5 Octave band centre frequency f
m
Topic: CNOSSOS -EU: 2015 is somewhat ambiguous about whether nominal centre frequencies or exact
centre frequencies should be used in the calculation of the atmospheric attenuation coefficient α .
atm
Agreed interpretation:
In the calculation of the atmospheric attenuation coefficient α , ISO 9613-1 is followed, and exact centre
atm
frequencies are used. In all other calculations, the nominal centre frequency, denoted f , are used.
m
The tabulated values in ISO 9613-1 are based on the pressure at sea level.
5.6 Ground factor of the source area, G
S
Topic : C NOS S OS -E U: 2015 i nt r o duc e s G in subclause 2.5.6 as the ground factor G of the source area. For
S
industrial sources, it is left open how exactly G is to be calculated.
S
Agreed interpretation:
For industrial point sources, G is calculated as the average of the ground factor G over a distance of 1 m
S
beginning at the vertical projection point below the source and proceeding along the direction source-
receiver.
5.7 Distances in Figure 2.5.b of CNOSSOS -EU: 2015
Topic: In CNOSSOS -EU: 2015, it is unclear whether the distances d displayed in Figure 2.5.b are
3D-distances along the ground or 2D-projection onto a horizontal plane.
Agreed interpretation:
Figure 2.5.b displays a 2D-projection onto the horizontal plane. The distances d used in the calculation
of G are measured in this horizontal plane.
path
5.8 Equivalent heights in Equation (2.5.20) of CNOSSOS -EU: 2015
Topic: CNOSSOS -EU: 2015 explains that modified equivalent heights should be used in the calculation of
A . But it is unclear whether these modified equivalent heights or unmodified equivalent heights
ground,F
should be used in the calculation of A according to Equation (2.5.20) of CNOSSOS -EU: 2015.
ground,F,min
Agreed interpretation:
Unmodified equivalent heights are used in the calculation of A according to Equation (2.5.20)
ground,F,min
of C NOS S OS -E U: 2015 .
5.9 Rayleigh’s Criterion
Topic: CNOSSOS -EU: 2015 states that no diffraction should be calculated if the ray path passes "high
enough" over the diffraction edge. In this context, CNOSSOS -EU: 2015 refers to Rayleigh’s Criterion
without providing details or formulae. The circumstances under which diffraction is calculated should
be defined unambiguously.
Agreed interpretation:
In the unique vertical plane containing source and receiver, the line of sight from source to receiver
is defined, under homogeneous conditions, as the straight line connecting source and receiver. Under
favourable conditions, the line of sight is defined as the arc of radius Γ, given by Equation (2.5.24) of
CNOSSOS -EU: 2015, connecting source and receiver.
The decision whether diffraction must be calculated is made separately for homogeneous and favourable
conditions respectively. If the line of sight is blocked, diffraction is always calculated. If the line of sight
from source to receiver is unobstructed, Rayleigh’s Criterion is employed as follows: first, that point
D of the terrain profile including obstacles is identified, which gives the largest δ , i.e. the δ with the
D D
smallest absolute value. Then δ * is calculated as the path length difference from S’ to R’ via D, where S’
D
and R’ are the respective images of source and receiver constructed with the appropriate mean ground
planes containing source or receiver. Diffraction is calculated only if δ > -λ/20 and δ > λ/4 - δ *
D D D
(Rayleigh’s Criterion), where λ is the wavelength at the nominal centre frequency and calculated with a
speed of sound of 340 m/s.
5.10 Parameter e
Topic: CNOSSOS -EU: 2015 introduces the parameter e as the total distance along the path from the first
to the last diffraction edge according to the "rubber band method". It is unclear how the parameter e is
calculated for favourable propagation conditions.
Agreed interpretation:
The parameter e is defined as the total distance along the path from the first to the last diffraction
edge. Under homogeneous conditions, straight lines are used as ray segments, while under favourable
conditions, arcs of uniform radius are used as ray segments. Different diffraction edges may be relevant
under homogeneous and favourable conditions respectively.
5.11 Diffraction under favourable conditions
Topic: CNOSSOS -EU: 2015 explains diffraction under favourable propagation conditions. The text
contains too little details to be unambiguous. In particular, the scale of Figure 2.5.f of CNOSSOS -EU:
2015 is chosen such that the ray segments appear to be straight lines while they should be arcs of radius
Γ, given by Equation (2.5.24) of CNOSSOS -EU: 2015.
Agreed interpretation:
Under favourable conditions, the propagation path in the vertical plane always consists of segments
of a circle whose radius is given by the 3D-distance between source and receiver according to
Equation (2.5.24) of CNOSSOS -EU: 2015, i.e. all segments of a propagation path have the same radius of
curvature. If the direct arc connecting source and receiver is blocked, the propagation path is defined
as the shortest convex combination of arcs enveloping all obstacles. Convex in this context means that
at each diffraction point, the outgoing ray segment is deflected downward with respect to the incoming
ray segment (see ISO 9613-1).
To illustrate the principle of constructing the ray path with multiple diffractions under favourable
conditions, Figure 2 is a slightly modified version of Figure 2.5.f of CNOSSOS -EU: 2015, scaled such that
the curvature of the rays is apparent.
4 © ISO 2020 – All rights reserved

Figure 2 — Modified version of Figure 2.5.f of CNOSSOS -EU: 2015 showing ray paths
with easily visible curvature
5.12 Error in Figure 2.5.f and Equation (2.5.29) of CNOSSOS -EU: 2015
Topic: Figure 2.5.f and Equation (2.5.29) of CNOSSOS -EU: 2015 are erroneous.
Agreed interpretation:
Figure 2.5.f and Equation (2.5.29) of CNOSSOS -EU: 2015 treat the point O as a diffraction edge, even
though it lies below the rubber band. This is incorrect. Given the geometry displayed in Figure 2.5.f of
CNOSSOS -EU: 2015, the right-hand edge of obstacle E2 cannot be treated as a diffraction edge. A
corrected version of Figure 2.5.f of CNOSSOS -EU: 2015 is displayed as Figure 3, with Equation (2.5.29)
    
of C NOS S OS -E U: 2015 r e ad i n g : δ =+SO OO ++OO OR−SR .
F 11 22 33
Figure 3 — Corrected version of Figure 2.5.f of CNOSSOS -EU: 2015
5.13 Lateral diffraction
Topic: CNOSSOS -EU: 2015 introduces lateral diffraction, i.e. diffraction on vertical edges. The description
is too short to be unambiguous. In particular, it is left open exactly how laterally diffracted propagation
paths are to be constructed.
Agreed interpretation:
As a general principle, lateral diffraction is considered only if the direct line of sight (see 5.9 above)
between source and receiver is blocked and does not penetrate the terrain profile. In addition, the
source must not be a mirror source due to reflection. This said, lateral diffraction edges are sought
in the unique plane which contains both source and receiver, and which is also perpendicular to the
vertical propagation plane. Obstacles are taken into account including adjoining obstacles. Obstacles
which penetrate this plane form an area of intersection with that plane. An intersection area is
only considered relevant if the corresponding obstacle is intersected by the direct line of sight. The
diffraction edges of lateral paths are defined by a rubber band that stretches from source to receiver,
left and right of the direct line of sight respectively, and encompasses all relevant intersection areas.
To calculate the ground attenuation for a laterally diffracted propagation path, a mean ground plane is
calculated for the terrain profile vertically below the propagation path between source and receiver.
This utilises a vertical X-Z auxiliary plane, whose Z coordinate corresponds to the absolute height, and
whose X coordinate corresponds to the distance from the source point along the propagation path in
the projection onto a horizontal plane. If a lateral propagation path in the projection onto a horizontal
plane intersects the ground layout of a building, this building is taken into account in the calculation of
G (usually with G=0) and in the calculation of the mean ground plane using its height. With respect
path
to the calculation of the ground attenuation, a laterally diffracted propagation path is treated in the
auxiliary X-Z plane as a propagation path with unblocked line of sight, and without diffraction.
5.14 Reflection on nearly vertical objects
Topic: CNOSSOS -EU: 2015 explains reflection on (nearly) vertical objects. Further specifications are
needed to formulate this aspect unambiguously.
Agreed interpretation:
Objects are considered as reflectors only if they slope less than 15° with respect to the vertical. For the
calculation of reflected sound with a mirror image source propagation is only considered in a vertical
propagation plane (i.e. not for laterally diffracted paths). The point of reflection, which lies on the
reflecting object, is constructed assuming the reflecting surface is vertical. Ray paths are constructed
for incident and reflected paths using straight lines under homogeneous conditions, and arcs under
favourable conditions.
The height of the reflector, as viewed from the direction of the incident ray and measured through
the point of reflection, is at least 0,5 m. The width of the reflector as viewed from the direction of the
incident ray in a horizontal plane containing this reflection point is at least 0,5 m.
5.15 Retrodiffraction
Topic: CNOSSOS -EU: 2015 describes the principle of retrodiffraction. It is unclear under which
circumstances retrodiffraction is to be considered and how retrodiffraction is dealt with under
favourable conditions.
Agreed interpretation:
Attenuation through retrodiffraction is calculated for every reflection.
The construction of the relevant path length difference δ’ is shown in Figure 4 for homogeneous
conditions. The upper edge of the reflector is used as fictitious diffraction edge and straight lines are
used as ray segments. The resulting path length difference is δ ''=−SO SP' −PO .
Figure 4 — Example for retrodiffraction under homogeneous conditions
Figure 5 depicts the same situation under favourable conditions. The construction is analogous to the
homogeneous case but uses arcs for ray segments, instead of straight lines. In this example, the resulting
   
path length difference becomes δ ''=+SO OR−−SP' PR .
Figure 5 — Example for retrodiffraction under favourable conditions
6 © ISO 2020 – All rights reserved

6 Test cases
6.1 General
The test cases are based on the series proposed with ISO/TR 17534-2, but extended to address special
aspects of CNOSSOS -EU: 2015. As mentioned in 5.13, diffraction on vertical edges is not described in
sufficient detail to be unambiguous in the official documentation. The sentence “Equation (2.5.21) may
be used to calculate the diffractions on vertical edges (lateral diffractions) in case of industrial noise”
opens many possibilities to treat this issue. According to the general requirements of Quality Assurance
in ISO 17534-1 it was necessary to provide a detailed specification – this is given in 5.13 above. Lateral
diffraction is restricted to industrial sources and ensures a continuous transition from the screened to
the unscreened position when the receiver moves horizontally behind the objects blocking the direct
line of sight. Unfortunately, lateral diffraction requires a lot of additional calculation steps.
Independent from the different national specifications (in which cases lateral diffraction is taken into
account) lateral diffraction is included in all test cases where it influences the result if the point source
is assumed to be an industrial facility, thus allowing for the certification of a correct implementation in
all cases. The test cases are complete in the sense that all data necessary to perform the calculations
are given.
Intermediate and final results are shown separately for the propagation in the vertical plane and for the
propagation around vertical edges – when only road-traffic and railway are of concern, the validation of
a quality assured implementation in accordance with ISO 17534-1 can be restricted to the propagation
in the vertical plane.
When testing a software implementation, the calculated A-weighted long-term sound pressure levels,
referred to as final results, are compared with the reference results given in 6.3 in Table 362 and
Table 363. A software implementation of CNOSSOS -EU: 2015 is considered quality assured in accordance
with ISO 17534-1 if – for all test cases – the deviation of the calculated final results from the reference
results does not exceed ±0,1 dB in any octave band. If some of the final results differ too much from the
reference results, the implementation is considered flawed. Intermediate results are provided – mostly
to two decimal places – to facilitate the necessary search for the deficiency of the implementation.
Test results and tolerances are based on experience with calculations made with different software
platforms.
Unless stated otherwise, the input parameters shown in Tables 1 and 2 apply to all test cases.
Table 1 — Input parameters identical for all test cases
p % 50
Relative humidity % 70
T °C 10
Table 2 — Linear octave-band sound power levels and A-weighting correction values
Octave-band centre frequency in Hz
Value
63 125 250 500 1 000 2 000 4 000 8 000
Sound power level
93 93 93 93 93 93 93 93
L in dB
W
A-weighting correction
−26,2 −16,1 −8,6 −3,2 0,0 1,2 1,0 −1,1
value in dB
In the Tables containing the parameters of the mean ground plane (MGP) and the heights z above this
MGP, the two abbreviations z and z are used. Their correspondence to the notation in CNOSSOS -EU:
1 2
2015 is shown in Table 3.
Table 3 — Correspondence between z and z , used in some Tables such as Table 18,
1 2
and z , z , z , z
s o,s o,r r
S -> R S -> O O -> R
1 n
z z z z
1 s s o,r
z z z z
2 r o,s r
6.2 Test cases with intermediate and final results
6.2.1 TC01-TC03 — Flat ground with homogeneous acoustic properties
The test cases to check free sound propagation with different conditions are shown in Figure 6.
Key
S source
R receiver
Figure 6 — Test cases TC01-TC03 to check free sound propagation with different conditions
With the first three test cases, the correct consideration of the ground factor G is checked. The terrain
is flat. Table 4 shows the coordinates of source and receiver which is identical for all three test cases.
Table 4 — Coordinates of source S and receiver R
x y z
Point
(m) (m) (m)
S 10 10 1
R 200 50 4
6.2.2 TC01 — Reflecting ground (G = 0)
Tables 5 and 6 contain the intermediate and the final results.
Table 5 — Ground attenuation (in frequency bands where no diffraction is relevant)
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
a
w (H) 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00
C (H) 194,16 194,16 194,16 194,16 194,16 194,16 194,16 194,16
f
A in dB -3,00 -3,00 -3,00 -3,00 -3,00 -3,00 -3,00 -3,00
ground,H
b
w (F) 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00
C (F) 194,16 194,16 194,16 194,16 194,16 194,16 194,16 194,16
f
A in dB -4,36 -4,36 -4,36 -4,36 -4,36 -4,36 -4,36 -4,36
ground,F
a
(H) – homogeneous
b
(F) – favourable
8 © ISO 2020 – All rights reserved

Table 6 — Step by step and final results related to the propagation in the vertical plane
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
L in dB 93 93 93 93 93 93 93 93
W
α 0,12 0,41 1,04 1,93 3,66 9,66 32,77 116,88
atm
A in dB 0,02 0,08 0,20 0,37 0,71 1,88 6,36 22,70
atm
A in dB 56,76 56,76 56,76 56,76 56,76 56,76 56,76 56,76
div
A in dB -3,00 -3,00 -3,00 -3,00 -3,00 -3,00 -3,00 -3,00
boundary,H
A in dB -4,36 -4,36 -4,36 -4,36 -4,36 -4,36 -4,36 -4,36 Total
boundary,F
L in dB 39,21 39,16 39,03 38,86 38,53 37,36 32,87 16,54 46,70
H
L in dB 40,58 40,52 40,40 40,23 39,89 38,72 34,24 17,90 48,07
F
L in dB 39,95 39,89 39,77 39,60 39,26 38,09 33,61 17,27 47,44
A-weighting in dB -26,2 -16,1 -8,6 -3,2 0,0 1,2 1,0 -1,1
L in dB 13,75 23,79 31,17 36,40 39,26 39,29 34,61 16,17 44,12
A
6.2.3 TC02 — Mixed ground (G = 0,5)
Tables 7 and 8 contain the intermediate and the final results.
Table 7 — Ground attenuation (in frequency bands where no diffraction is relevant)
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
w (H) 8,2E-05 4,5E-04 2,5E-03 0,01 0,08 0,41 2,10 10,13
C (H) 199,17 213,44 225,43 134,05 23,76 2,49 0,47 0,10
f
A in dB -1,50 -1,50 -1,50 0,85 5,71 -1,50 -1,50 -1,50
ground,H
w (F) 0,00 0,00 0,00 0,01 0,08 0,41 2,10 10,13
C (F) 199,17 213,44 225,43 134,05 23,76 2,49 0,47 0,10
f
A in dB -2,18 -2,18 -2,18 -2,18 -0,93 -2,18 -2,18 -2,18
ground,F
Table 8 — Step by step and final results related to the propagation in the vertical plane
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
L in dB 93 93 93 93 93 93 93 93
W
α 0,12 0,41 1,04 1,93 3,66 9,66 32,77 116,88
atm
A in dB 0,02 0,08 0,20 0,37 0,71 1,88 6,36 22,70
atm
A in dB 56,76 56,76 56,76 56,76 56,76 56,76 56,76 56,76
div
A in dB -1,50 -1,50 -1,50 0,85 5,71 -1,50 -1,50 -1,50
boundary,H
Table 8 (continued)
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
A in dB -2,18 -2,18 -2,18 -2,18 -0,93 -2,18 -2,18 -2,18 Total
boundary,F
L in dB 37,71 37,66 37,53 35,01 29,82 35,86 31,37 15,04 44,28
H
L in dB 38,39 38,34 38,22 38,04 36,45 36,54 32,05 15,72 45,72
F
L in dB 38,07 38,01 37,89 36,79 34,29 36,21 31,73 15,39 45,06
A-weighting in dB -26,2 -16,1 -8,6 -3,2 0,0 1,2 1,0 -1,1
L in dB 11,87 21,91 29,29 33,59 34,29 37,41 32,73 14,29 41,27
A
6.2.4 TC03 — Porous ground (G = 1)
Tables 9 and 10 contain the intermediate and the final results.
Table 9 — Ground attenuation (in frequency bands where no diffraction is relevant)
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
w (H) 4,9E-04 2,7E-03 1,5E-02 0,08 0,41 2,02 9,06 35,59
C (H) 214,47 224,67 130,15 22,76 2,48 0,49 0,11 0,03
f
A in dB 0,00 0,00 1,59 9,67 5,03 0,00 0,00 0,00
ground,H
w (F) 0,00 0,00 0,01 0,08 0,41 2,02 9,06 35,59
C (F) 214,47 224,67 130,15 22,76 2,48 0,49 0,11 0,03
f
A in dB 0,00 0,00 0,00 4,23 0,00 0,00 0,00 0,00
ground,F
Table 10 — Step by step and final results related to the propagation in the vertical plane
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
L in dB 93 93 93 93 93 93 93 93
W
α 0,12 0,41 1,04 1,93 3,66 9,66 32,77 116,88
atm
A in dB 0,02 0,08 0,20 0,37 0,71 1,88 6,36 22,70
atm
A in dB 56,76 56,76 56,76 56,76 56,76 56,76 56,76 56,76
div
A in dB 0,00 0,00 1,59 9,67 5,03 0,00 0,00 0,00
boundary,H
A in dB 0,00 0,00 0,00 4,23 0,00 0,00 0,00 0,00 Total
boundary,F
L in dB 36,21 36,16 34,45 26,19 30,49 34,36 29,87 13,54 42,14
H
L in dB 36,21 36,16 36,03 31,63 35,53 34,36 29,87 13,54 43,24
F
L in dB 36,21 36,16 35,31 29,71 33,70 34,36 29,87 13,54 42,72
A-weighting in dB -26,2 -16,1 -8,6 -3,2 0,0 1,2 1,0 -1,1
L in dB 10,01 20,06 26,71 26,51 33,70 35,56 30,87 12,44 39,14
A
6.2.5 TC04 — Flat ground with spatially varying acoustic properties
The aim of this test case is to check the correct consideration and averaging of varying ground factors
G. This test case is shown in Figure 7.
10 © ISO 2020 – All rights reserved

Key
S source
R receiver
A1 area with G = 0,2
A2 area with G = 0,5
A3 area with G = 0,9
Figure 7 — Flat ground with different ground factors G
Table 11 contains the parameters of the areas with constant ground factor G, and Tables 12 to 14 show
the detailed intermediate and the final results.
Table 11 — Rectangular areas with constant ground factor G
G x y
(m) (m)
min max min max
0,2 0,0 50,0 -20,0 80,0
0,5 50,0 150,0 -20,0 80,0
0,9 150,0 225,0 -20,0 80,0
Table 12 — G-profile (ground factor) along the propagation path
G-profile S -> R
from to length G
(m) (m) (m)
0,00 40,88 40,88 0,2
40,88 143,07 102,19 0,5
143,07 194,16 51,09 0,9
Table 13 — Ground attenuation (in frequency bands where no diffraction is relevant)
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
w (H) 1,0E-04 5,6E-04 3,1E-03 0,02 0,09 0,50 2,53 11,96
C (H) 200,18 216,12 221,91 116,87 17,87 2,02 0,39 0,08
f
A in dB -1,37 -1,37 -1,37 1,77 6,23 -1,37 -1,37 -1,37
ground,H
w (F) 0,00 0,00 0,00 0,02 0,09 0,50 2,53 11,96
C (F) 200,18 216,12 221,91 116,87 17,87 2,02 0,39 0,08
f
A in dB -2,00 -2,00 -2,00 -2,00 -0,95 -2,00 -2,00 -2,00
ground,F
Table 14 — Step by step and final results related to the propagation in the vertical plane
f in Hz 63 125 250 500 1 000 2 000 4 000 8 000
L in dB 93 93 93 93 93 93 93 93
W
α 0,12 0,41 1,04 1,93 3,66 9,66 32,77 116,88
atm
A in dB 0,02 0,08 0,20 0,37 0,71 1,88 6,36 22,70
atm
A in dB 56,76 56,76 56,76 56,76 56,76 56,76 56,76 56,76
div
A in dB -1,37 -1,37 -1,37 1,77 6,23 -1,37 -1,37 -1,37
boundary,H
A
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