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Document 32021L1226

Commission Delegated Directive (EU) 2021/1226 of 21 December 2020 amending, for the purposes of adapting to scientific and technical progress, Annex II to Directive 2002/49/EC of the European Parliament and of the Council as regards common noise assessment methods (Text with EEA relevance)


OJ L 269, 28.7.2021, p. 65–142 (BG, ES, CS, DA, DE, ET, EL, EN, FR, GA, HR, IT, LV, LT, HU, MT, NL, PL, PT, RO, SK, SL, FI, SV)

Legal status of the document In force




Official Journal of the European Union

L 269/65


of 21 December 2020

amending, for the purposes of adapting to scientific and technical progress, Annex II to Directive 2002/49/EC of the European Parliament and of the Council as regards common noise assessment methods

(Text with EEA relevance)


Having regard to the Treaty on the Functioning of the European Union,

Having regard to Directive 2002/49/EC of the European Parliament and of the Council of 25 June 2002 relating to the assessment and management of environmental noise (1), and in particular Article 12 thereof,



Annex II to Directive 2002/49/EC sets methods of assessment common to the Member States, to be used for the information on environmental noise and its effects on health, in particular for noise mappings, and to adopt action plans based upon noise mapping results. This annex needs to be adapted to technical and scientific progress.


From 2016 to 2020, the Commission cooperated with technical and scientific experts of the Member States to assess which adaptations were needed taking into account the technical and scientific advances in the calculation of environmental noise. This process was carried out in close consultation with the Noise Expert Group, composed of Member States, the European Parliament, industry stakeholders, public authorities of Member States, NGOs, citizens and academia.


The Annex to this Delegated Directive sets out the necessary adaptations of the common assessment methods consisting of clarification of formulas to calculate the propagation of noise, adaptation of tables to the latest knowledge and improvements in the description of the steps of the calculations. This affects road noise, railway noise, industrial noise and aircraft noise calculations. Member States are required to use these methods at the latest from 31 December 2021.


Annex II to Directive 2002/49/EC should therefore be amended accordingly.


The measures provided for in this Directive are in accordance with the opinion of the Noise Expert Group consulted on 12 October 2020,


Article 1

Annex II to Directive 2002/49/EC is amended in accordance with the Annex to this Directive.

Article 2

1.   Member States shall bring into force the laws, regulations and administrative provisions necessary to comply with this Directive by 31 December 2021 at the latest. They shall immediately communicate the text of those measures to the Commission.

When Member States adopt those measures, they shall contain a reference to this Directive or be accompanied by such a reference on the occasion of their official publication. Member States shall determine how such reference is to be made.

2.   Member States shall communicate to the Commission the text of the main provisions of national law which they adopt in the field covered by this Directive.

Article 3

This Directive shall enter into force on the day following that of its publication in the Official Journal of the European Union.

Article 4

This Directive is addressed to the Member States.

Done at Brussels, 21 December 2020.

For the Commission

The President


(1)   OJ L 189, 18.7.2002, p. 12.


Annex II is amended as follows:


In Section 2.1.1, the second paragraph is replaced by the following:

‘Calculations are performed in octave bands for road traffic, railway traffic and industrial noise, except for the railway noise source sound power, which uses third octave bands. For road traffic, railway traffic and industrial noise, based on these octave band results, the A-weighted long-term average sound level for the day, evening and night period, as defined in Annex I and referred to in Article 5 of Directive 2002/49/EC, is computed by the method described in Sections 2.1.2, 2.2, 2.3, 2.4 and 2.5. For roads and railway traffic in agglomerations, the A-weighted long-term average sound level is determined by the contribution from road and railway segments therein, including major roads and major railways.’.


Section 2.2.1 is amended as follows:


in the paragraph under the heading ‘Number and Position of Equivalent Sound Sources’, the first sub-paragraph is replaced by the following:

‘In this model, each vehicle (category 1, 2, 3, 4 and 5) is represented by one single point source radiating uniformly. The first reflection on the road surface is treated implicitly. As depicted in Figure [2.2.a], this point source is placed 0,05 m above the road surface.’;


in the paragraph under the heading ‘Sound Power Emission’, the last sub-paragraph under the heading ‘Traffic Flow’ is replaced by the following:

‘The speed vm is a representative speed per vehicle category: in most cases the lower of the maximum legal speed for the section of road and the maximum legal speed for the vehicle category.’;


in the paragraph under the heading ‘Sound Power Emission’, the first sub-paragraph under the heading ‘Individual vehicle’ is replaced by the following:

‘In the traffic flow, all vehicles of category m are assumed to drive at the same speed, i.e. vm ’.


Table 2.3.b is amended as follows:


in the third row, fourth column (called ‘3’), the text is replaced by the following:

‘Represents an indication of the “dynamic” stiffness’;


in the sixth row, fourth column (called ‘3’), the text is replaced by the following:


Hard (800-1 000MN/m)’.


Section 2.3.2 is amended as follows:


in the paragraph under the heading ‘Traffic Flow’, the fourth sub-paragraph, the second indent under formula (2.3.2), is replaced by the following:


v is their speed [km/h] in the j-th track section for vehicle type t and average train speed s ’;


the paragraph under the headings ‘Squeal’ is replaced by the following:

‘Curve squeal is a special source that is only relevant for curves and is therefore localised. Curve squeal is generally dependent on curvature, friction conditions, train speed, track-wheel geometry and dynamics. As it can be significant, an appropriate description is required. At locations where curve squeal occurs, generally in curves and turnouts of railway switches, suitable excess noise power spectra need to be added to the source power. The excess noise may be specific to each type of rolling stock, as certain wheel and bogie types may be significantly less prone to squeal than others. If measurements of the excess noise are available that take sufficiently the stochastic nature of squeal into account, these may be used.

If no appropriate measurements are available, a simple approach can be taken. In this approach, squeal noise shall be considered by adding the following excess values to the rolling noise sound power spectra for all frequencies.


5 dB for curves with 300 m < R ≤ 500m and ltrack ≥ 50m

8 dB for curves with R ≤ 300m and ltrack ≥ 50m

8 dB for switch turnouts with R ≤ 300m

0 dB otherwise


5 dB for curves and switch turnouts with R ≤ 200 m

0 dB otherwise

where ltrack is the length of track along the curve and R is the curve radius.

The applicability of these sound power spectra or excess values shall normally be verified on-site, especially for trams and for locations where curves or turnouts are treated with measures against squeal.’;


the paragraph under the headings ‘Source directivity’, directly after equation (2.3.15) the following is added:

‘Bridge noise is modelled at source A (h = 1), for which omni-directionality is assumed.’;


the paragraph under the headings ‘Source Directivity’, the second sub-paragraph until and including formula 2.3.16 is replaced by the following:

The vertical directivity ΔLW,dir,ver,i in dB is given in the vertical plane for source A (h = 1), as a function of the centre band frequency fc,i of each i-th frequency band, and:

for 0 < ψ < π/2 is

Image 1

for - π/2< ψ <=0 is

ΔLW,dir,ver,i = 0



In Section 2.3.3, the paragraph under the headings ‘Correction for structural radiation (bridges and viaducts)’ is replaced by the following:

Correction for structural radiation (bridges and viaducts)

In the case where the track section is on a bridge, it is necessary to consider the additional noise generated by the vibration of the bridge as a result of the excitation caused by the presence of the train. The bridge noise is modelled as an additional source of which the sound power per vehicle is given by

LW,0,bridge,i = LR,TOT,i + LH,bridge,i + 10 x lg(Na ) dB


where LH, bridge ,i is the bridge transfer function. The bridge noise LW,0, bridge ,i represents only the sound radiated by the bridge construction. The rolling noise from a vehicle on the bridge is calculated using (2.3.8) through (2.3.10), by choosing the track transfer function that corresponds to the track system that is present on the bridge. Barriers on the edges of the bridge are generally not taken into account.’.


Section 2.4.1 is amended as follows:


in the paragraph under the headings ‘Sound Power Emission – general’, the second sub-paragraph, the whole fourth element of the list including formula (2.4.1) is replaced by the following:


source lines representing moving vehicles are calculated according to formula 2.2.1’;


the number of the formula (2.4.2) is replaced by the following:



In Section 2.5.1, the seventh paragraph is replaced by the following:

‘Objects sloping more than 15° in relation to the vertical are not considered as reflectors but taken into account in all other aspects of propagation, such as ground effects and diffraction.’.


Section 2.5.5 is amended as follows:


in the paragraph under the headings ‘Sound level in favourable conditions (LF) for a path (S,R)’, the formula 2.5.6 is replaced by the following:

AF=Adiv + Aatm + Aboundary,F



in the paragraph under the headings ‘Long-term sound level at point R in decibels A (dBA)’, the end of the first sub-paragraph below the formula 2.5.11, is replaced by the following:

‘where i is the index of the frequency band. AWC is the A-weighting correction as follows:

Frequency [Hz]





1 000

2 000

4 000

8 000

AWCf,i [dB]










Section 2.5.6 is amended as follows:


directly below Figure 2.5.b, the following sentence is added:

‘The distances dn are determined by a 2D projection on the horizontal plane.’;


the sub-paragraph under the headings ‘Calculation in Favourable Conditions’ is amended as follows:


the first sentence of point (a) is replaced by the following:

‘In equation 2.5.15 (Aground,H ) the heights zs and zr are replaced by zs + δ zs + δ zT and zr + δ zr + δ zT respectively where’;


the first sentence of point (b) is replaced by the following:

‘The lower bound of Aground,F (calculated with unmodified heights) depends on the geometry of the path:’;


in the paragraph under the heading ‘Diffraction’, the second sub-paragraph is replaced by the following:

‘In practice, the following specifications are considered in the unique vertical plane containing both source and receiver (a flattened Chinese Screen in case of a path including reflections). The direct ray from source to receiver is a straight line under homogeneous propagation conditions and a curved line (arc with radius depending on the length of the straight ray) under favorable propagation conditions.

If the direct ray is not blocked, the edge D is sought which produces the largest path length difference δ (the smallest absolute value because these path length differences are negative). Diffraction is taken into account if:

this path length difference is larger than -λ/20, and

if the “Rayleigh-criterion” is fulfilled.

This is the case, if δ is larger than λ/4 – δ*, where δ* is the path length difference calculated with this same edge D but related to the mirror source S* calculated with the mean ground plane at the source side and the mirror receiver R* calculated with the mean ground plane at the receiver side. To calculate δ* only the points S*, D and R* are taken into account – other edges blocking the path S*->D->R* are neglected.

For the above considerations, the wavelength λ is calculated using the nominal centre frequency and a speed of sound of 340 m/s.

If these two conditions are fulfilled, the edge D separates the source side from the receiver side, two separate mean ground planes are calculated, and A dif is calculated as described in the remainder of this part. Otherwise, no attenuation by diffraction is considered for this path, a common mean ground plane for the path S -> R is calculated, and A ground is calculated with no diffraction (A dif = 0 dB). This rule applies in both homogeneous and favourable conditions.’;


in the paragraph under the heading ‘Pure Diffraction’, the second sub-paragraph is replaced by the following:

‘For a multiple diffraction, if e is the total path length distance between first and last diffraction point (use curved rays in case of favourable conditions) and if e exceeds 0,3 m (otherwise C" = 1), this coefficient is defined by:

Image 2



the Figure 2.5.d is replaced by the following:

Image 3


in the paragraph under the headings ‘Favourable Conditions’, the first sub-paragraph under Figure 2.5.e is replaced by the following:

‘In favourable conditions the three curved sound rays

Image 4
Image 5
, and
Image 6
have an identical radius of curvature Γ defined by:

Γ = max (1 000,8 d)


Where d is defined by the 3D distance between source and receiver of the unfolded path.’;


in the paragraph under the headings ‘Favourable Conditions’, the sub-paragraphs between formula (2.5.28) and formula (2.5.29) (the two formulas included), are replaced by the following:

Image 7


Under favourable conditions, the propagation path in the vertical propagation plane always consists of segments of a circle whose radius is given by the 3D-distance between source and receiver, that is to say, 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.

Image 8
Figure 2.5.f Example of calculation of the path difference in favourable conditions, in the case of multiple diffractions

In the scenario presented in Figure 2.5.f, the path difference is:

Image 9



the paragraphs respectively under the headings ‘Calculation of the term Δground(S,O)’ and ‘Calculation of the term Δground(O,R)’ are replaced by the following:

Calculation of the term Δground(S,O)

Image 10



Aground(S,O) is the attenuation due to the ground effect between the source S and the diffraction point O. This term is calculated as indicated in the previous subsection on calculations in homogeneous conditions and in the previous subsection on calculation in favourable conditions, with the following hypotheses:


Gpath is calculated between S and O;

In homogeneous conditions:

Image 11
in Equation (2.5.17),
Image 12
in Equation (2.5.18);

In favourable conditions:

Image 13
in Equation (2.5.17),
Image 14
in Equation (2.5.20);

Δ dif(S',R) is the attenuation due to the diffraction between the image source S’ and R, calculated as in the previous subsection on Pure diffraction;

Δ dif(S,R) is the attenuation due to the diffraction between S and R, calculated as in the previous subsection on Pure diffraction.

In the special case where the source lies below the mean ground plane: Δ dif(S,R) = Δ dif(S',R) and Δ ground(S,O) = A ground(S,O)

Calculation of the term Δground(O,R)

Image 15



Aground (O,R) is the attenuation due to the ground effect between the diffraction point O and the receiver R. This term is calculated as indicated in the previous subsection on calculation in homogeneous conditions and in the previous subsection on calculation in favourable conditions, with the following hypotheses:

z s = z o,r

Gpath is calculated between O and R.

The G’path correction does not need to be taken into account here, as the considered source is the diffraction point. Therefore, Gpath shall indeed be used in the calculation of ground effects, including for the lower bound term of the equation which becomes -3(1- Gpath ).

In homogeneous conditions,

Image 16
in Equation (2.5.17) and
Image 17
in Equation (2.5.18).

In favourable conditions,

Image 18
in Equation (2.5.17) and
Image 19
in Equation (2.5.20).

Δ dif(S,R’) is the attenuation due to the diffraction between S and the image receiver R’, calculated as in the previous section on pure diffraction.

Δ dif(S,R) is the attenuation due to the diffraction between S and R, calculated as in the previous subsection on pure diffraction.

In the special case where the receiver lies below the mean ground plane: Δ dif(S,R’) = Δ dif(S,R) and Δ ground ( O,R ) = A ground ( O,R ) ’’;


in Section 2.5.6, the paragraph under the headings ‘Vertical Edge Scenarios’ is replaced by the following:

Vertical Edge Scenarios

Equation (2.5.21) may be used to calculate the diffractions on vertical edges (lateral diffractions) in case of industrial noise. If this is the case, Adif = Δdif(S,R) is taken and the term Aground is kept. In addition, Aatm and Aground shall be calculated from the total length of the propagation path. Adiv is still calculated from the direct distance d. Equations (2.5.8) and (2.5.6) respectively become:

Image 20


Image 21


Δdif is indeed used in homogeneous conditions in equation (2.5.34).

Lateral diffraction is considered only in cases, where the following conditions are met:


The source is a real point source – not produced by segmentation of an extended source like a line- or area source.


The source is not a mirror source constructed to calculate a reflection.


The direct ray between source and receiver is entirely above the terrain profile.


In the vertical plane containing S and R the path length difference δ is larger than 0, that is to say, the direct ray is blocked. Therefore, in some situations, lateral diffraction may be considered under homogeneous propagation conditions but not under favourable propagation conditions.

If all these conditions are met, up to two laterally diffracted propagation paths are taken into account in addition to the diffracted propagation path in the vertical plane containing source and receiver. The lateral plane is defined as the plane that is perpendicular to the vertical plane and also contains source and receiver. The intersection areas with this lateral plane are constructed from all obstacles that are penetrated by the direct ray from source to receiver. In the lateral plane, the shortest convex connection between source and receiver, consisting of straight segments and encompassing these intersection areas, defines the vertical edges that are taken into account when the laterally diffracted propagation path is constructed.

To calculate ground attenuation for a laterally diffracted propagation path, the mean ground plane between the source and the receiver is calculated taking into account the ground profile vertically below the propagation path. If, in the projection onto a horizontal plane, a lateral propagation path cuts the projection of a building, this is taken into account in the calculation of Gpath (usually with G = 0) and in the calculation of the mean ground plane with the vertical height of the building.’;


in the paragraph under the headings ‘Reflections on vertical obstacles – Attenuation through absorption’, the second and third sub-paragraphs are replaced by the following:

‘Surfaces of objects are only considered as reflectors if their slopes are less than 15° with respect to the vertical. Reflections are considered only for paths in the vertical propagation plane, that is to say, not for laterally diffracted paths. For the incident and reflected paths, and assuming the reflecting surface is to be vertical, the point of reflection (which lays on the reflecting object) is constructed using straight lines under homogeneous and curved lines under favourable propagation conditions. The height of the reflector, when measured through the point of reflection and viewed from the direction of the incident ray, shall be at least 0,5 m. After projection onto a horizontal plane, the width of the reflector when measured through the point of reflection and viewed from the direction of the incident ray, shall be at least 0,5 m.’;


in the paragraph under the headings ‘Attenuation through retrodiffraction’, the following is added to the end of the existing text:

‘When there is a reflecting noise barrier or obstacle close to the railway track, the sound rays from the source are successively reflected off this obstacle and off the lateral face of the railway vehicle. In these conditions, the sound rays pass between the obstacle and railway vehicle body before diffraction from the top edge of the obstacle.

To take multiple reflections between railway vehicle and a nearby obstacle into account, the sound power of a single equivalent source is calculated. In this calculation, ground effects are ignored.

To derive the sound power of the equivalent source the following definitions apply:

The origin of the coordinate system is the nearside railhead

A real source, is located at S (ds =0, hs ), where hs is the height of the source relative to the railhead

The plane h = 0 defines the cars’ body

A vertical obstacle with top at B (dB , hb )

A receiver located at a distance dR > 0 behind the obstacle where R has coordinates (dB+dR , hR )

The inner side of the obstacle has absorption coefficients α(f) per octave band. The railway vehicle body has an equivalent reflection coefficient Cref . Normally Cref is equal to 1. Only, in the case of open flat-bed freight wagons a value of 0 can be used. If dB >5hB or α(f)>0,8 no train barrier interaction is taken into account.

In this configuration, multiple reflections between the railway vehicle body and the obstacle can be calculated using image sources positioned at Sn (dn = -2n. dB, hn = hs), n=0,1,2,..N; as shown in the Figure 2.5.k.

Image 22
Figure 2.5.k

The sound power of the equivalent source is expressed by:

Image 23


Where the sound power of the partial sources is given by:

LW,n = LW + ΔLn

ΔLn= ΔLgeo,n + ΔLdif,n + ΔLabs,n + ΔLref,n + ΔLretrodif,n



the sound power of the real source


a correction term for spherical divergence


a correction term for diffraction by the top of the obstacle


a correction term for the absorption at the inner side of the obstacle


a correction term for reflection from the railway vehicle body


a correction term for the finite height of the obstacle as a reflector

The correction for spherical divergence is given by

Image 24


Image 25


The correction for diffraction by the top of the obstacle is given by:


ΔLdif,n = D0 - Dn


Where Dn is the attenuation due to diffraction, calculated by means of formula 2.5.21 where C'' = 1 , for the path linking source Sn to receiver R, taking into account diffraction at the top of the obstacle B:

δ n = ± (|SnB| + |BR| - |SnR|)


The correction for absorption on the inner side of the obstacle is given by:

ΔLabs,n = 10•n•lg (1-α)


The correction for reflection from the railway vehicle body is given by:

ΔLref,n = 10•n•lg (Cref)


The correction for the finite height of the reflecting obstacle is taken into account by means of retro-diffraction. The ray path corresponding to an image of order N > 0 will be reflected n times by the obstacle. In the cross section, these reflections take place at distances

di = – (2i-q)db, i = 1,2,..n Where Pi (d = di, h = hb ), i = 1,2,..n as the tops of these reflecting surfaces. At each of these points a correction term is calculated as:

Image 26


Where Δ retrodif,n,i is calculated for a source at position Sn an obstacle top at Pi and a receiver at position R’. The position of the equivalent receiver R’ is given by R’=R if the receiver is above line of sight from Sn to B; otherwise the equivalent receiver position is taken on the line of sight vertically above the real receiver; namely:

dR' = dR


Image 27



Section 2.7.5 ‘Aircraft noise and performance’, is replaced by the following:

‘2.7.5    Aircraft noise and performance

The ANP database provided in Appendix I contains aircraft and engine performance coefficients, departure and approach profiles as well as NPD relationships for a substantial proportion of civil aircraft operating from European Union airports. For aircraft types or variants for which data are not currently listed, they can best be represented by data for other, normally similar, aircrafts that are listed.

This data was derived to calculate noise contours for an average or representative fleet and traffic mix at an airport. It may not be appropriate to predict absolute noise levels of an individual aircraft model and is not suitable to compare the noise performance and characteristics of specific aircraft types, models or a specific fleet of aircraft. Instead, to determine which aircraft types, models or specific fleet of aircrafts are the noisiest contributors, the noise certificates shall be looked at.

The ANP database includes one or several default take-off and landing profiles for each aircraft type listed. The applicability of these profiles to the airport under consideration shall be examined, and either the fixed-point profiles or the procedural steps that best represent the flight operations at this airport shall be determined.’.


In Section 2.7.11, the title of the second paragraph under the headings ‘Track dispersion’ is replaced by the following:

Lateral track dispersion ’.


In Section 2.7.12, after the sixth sub-paragraph and before the seventh and last sub-paragraph, the following sub-paragraph is inserted:

‘An aircraft noise source should be entered at a minimum height of 1,0m (3,3ft) above the aerodrome level, or above the terrain elevation levels of the runway, as relevant.’.


Section 2.7.13, ‘Construction of flight path segments’, is replaced by the following:

‘2.7.13    Construction of flight path segments

Each flight path has to be defined by a set of segment coordinates (nodes) and flight parameters. The starting point is to determine the co-ordinates of the ground track segments. The flight profile is then calculated, remembering that for a given set of procedural steps, the profile depends on the ground track; e.g. at the same thrust and speed the aircraft climb rate is less in turns than in straight flight. Sub-segmentation is then undertaken for the aircraft on the runway (takeoff or landing ground roll), and for the aircraft near to the runway (initial climb or final approach). Airborne segments with significantly different speeds at their start and end points should then be sub-segmented. The two-dimensional co-ordinates of the ground track (*) segments are determined and merged with the two-dimensional flight profile to construct the three-dimensional flight path segments. Finally, any flight path points that are too close together are removed.

Flight profile

The parameters describing each flight profile segment at the start (suffix 1) and end (suffix 2) of the segment are:

s1, s2

distance along the ground track,

z1, z2

aeroplane height,

V1 , V2


P1 , P2

noise-related power parameter (matching that for which the NPD-curves are defined), and

ε1, ε 2

bank angle.

To build a flight profile from a set of procedural steps (flight path synthesis), segments are constructed in sequence to achieve required conditions at the end points. The end-point parameters for each segment become the start-point parameters for the next segment. In any segment calculation the parameters are known at the start; required conditions at the end are specified by the procedural step. The steps themselves are defined either by the ANP defaults or by the user (e.g. from aircraft flight manuals). The end conditions are usually height and speed; the profile building task is to determine the track distance covered in reaching those conditions. The undefined parameters are determined via flight performance calculations described in Appendix B.

If the ground track is straight, the profile points and associated flight parameters can be determined independently of the ground track (bank angle is always zero). However ground tracks are rarely straight; they usually incorporate turns and, to achieve best results, these have to be accounted for when determining the 2-dimensional flight profile, where necessary splitting profile segments at ground track nodes to inject changes of bank angle. As a rule the length of the next segment is unknown at the outset and it is calculated provisionally assuming no change of bank angle. If the provisional segment is then found to span one or more ground track nodes, the first being at s, namely s1 < s < s2 , the segment is truncated at s, calculating the parameters there by interpolation (see below). These become the end-point parameters of the current segment and the start-point parameters of a new segment – which still has the same target end conditions. If there is no intervening ground track node the provisional segment is confirmed.

If the effects of turns on the flight profile are to be disregarded, the straight flight, single segment solution is adopted although the bank angle information is retained for subsequent use.

Whether or not turn effects are fully modelled, each 3-dimensional flight path is generated by merging its 2-dimensional flight profile with its 2-dimensional ground track. The result is a sequence of co-ordinate sets (x,y,z), each being either a node of the segmented ground track, a node of the flight profile or both, the profile points being accompanied by the corresponding values of height z, ground speed V, bank angle ε and engine power P. For a track point (x,y) which lies between the end points of a flight profile segment, the flight parameters are interpolated as follows:

z = z1 + f ·(z2 – z1)


Image 28


ε = ε1 + f · (ε2 - ε1)


Image 29



f = (s - s 1)/(s 2 - s 1)


Note that whilst z and ε are assumed to vary linearly with distance, V and P are assumed to vary linearly with time (namely constant acceleration (**)).

When matching flight profile segments to radar data (flight path analysis) all end-point distances, heights, speeds and bank angles are determined directly from the data; only the power settings have to be calculated using the performance equations. As the ground track and flight profile coordinates can also be matched appropriately, this is usually quite straightforward.

Takeoff ground roll

When taking off, as an aircraft accelerates between the point of brake release (alternatively termed Start-of-Roll SOR) and the point of lift-off, speed changes dramatically over a distance of 1 500 to 2 500 m, from zero to between around 80 and 100 m/s.

The takeoff roll is thus divided into segments with variable lengths over each of which the aircraft speed changes by specific increment ΔV of no more than 10 m/s (about 20 kt). Although it actually varies during the takeoff roll, an assumption of constant acceleration is adequate for this purpose. In this case, for the takeoff phase, V1 is initial speed, V2 is the takeoff speed, nTO is the number of takeoff segment and sTO is the equivalent takeoff distance. For equivalent takeoff distance sTO (see Appendix B) and takeoff speed V1 and takeoff speed VTO the number nTO of segments for the ground roll is

nTO = int (1 + (VTO - V 1) /10)


and hence the change of velocity along a segment is



and the time Δt on each segment is (constant acceleration assumed)

Image 30


The length sTO,k of segment k (1 ≤ k ≤ nTO) of the takeoff roll is then:

Image 31


Example: For a takeoff distance sTO  = 1 600 m, V1 = 0m/s and V2 = 75 m/s, this yields nTO  = 8 segments with lengths ranging from 25 to 375 metres (see Figure 2.7.g):

Image 32
Figure 2.7.g Segmentation of a takeoff roll (example for 8 segments)

Similarly to the speed changes, the aircraft thrust changes over each segment by a constant increment ΔP, calculated as

ΔP = (PTO - Pinit ) / nTO


where PTO and P init respectively designate the aircraft thrust at the point of lift-off and the aircraft thrust at the start of takeoff roll.

The use of this constant thrust increment (instead of using the quadratic form equation 2.7.6) aims at being consistent with the linear relationship between thrust and speed in the case of jet-engine aircraft.

Important note: The above equations and example implicitly assume that the initial speed of the aircraft at the start of the takeoff phase is zero. This corresponds to the common situation where the aircraft starts to roll and accelerate from the brake release point. However, there are also situations where the aircraft may start to accelerate from its taxiing speed, without stopping at the runway threshold. In that case of non-zero initial speed Vinit the following “generalised” equations should be used in replacement of equations 2.7.8, 2.7.9. 2.7.10 and 2.7.11.

Image 33


In this case, for the takeoff phase, V1  is initial speed Vinit , V2  is the takeoff speed VTO , n is the number of takeoff segment nTO , s is the equivalent takeoff distance sTO and sk  is the length sTO,k  of segment k (1[Symbol]k[Symbol]n).

The landing ground roll

Although the landing ground roll is essentially a reversal of the takeoff ground roll, special account has to be taken of

reverse thrust which is sometimes applied to decelerate the aircraft, and

aeroplanes leaving the runway after deceleration (aircraft that leave the runway no longer contribute to air noise as noise from taxiing is disregarded).

In contrast to the takeoff roll distance, which is derived from aircraft performance parameters, the stop distance sstop (namely the distance from touchdown to the point where the aircraft leaves the runway) is not purely aircraft specific. Although a minimum stop distance can be estimated from aircraft mass and performance (and available reverse thrust), the actual stop distance depends also on the location of the taxiways, on the traffic situation, and on airport-specific regulations on the use of reverse thrust.

The use of reverse thrust is not a standard procedure – it is only applied if the needed deceleration cannot be achieved by the use of the wheel brakes. (Reverse thrust can be exceptionally disturbing as a rapid change of engine power from idle to reverse settings produces a sudden burst of noise.)

However, most runways are used for departures as well as for landings so that reverse thrust has a very small effect on the noise contours since the total sound energy in the vicinity of the runway is dominated by the noise produced from takeoff operations. Reverse thrust contributions to contours may only be significant when runway use is limited to landing operations.

Physically, reverse thrust noise is a very complex process but because of its relatively minor significance to air noise contours it can be modelled simplistically – the rapid change in engine power being taken into account by suitable segmentation.

It is clear that modelling the landing ground roll is less straightforward than for takeoff roll noise. The following simplified modelling assumptions are recommended for general use, when no detailed information is available (see Figure 2.7.h.1).

Image 34
Figure 2.7.h.1 Modelling of landing ground roll

The aircraft crosses the landing threshold (which has the co-ordinate s = 0 along the approach ground track) at an altitude of 50 feet, and then continues to descend on its glideslope until it touches down on the runway. For a 3° glideslope, the touch-down point is 291 m beyond the landing threshold (as illustrated in Figure 2.7.h.1). The aircraft is then decelerated over a stop-distance sstop – aircraft specific values of which are given in the ANP database – from final approach speed Vfinal to 15 m/s. Because of the rapid changes in speed during this segment it should be sub-segmented in the same manner as for the takeoff ground roll (or airborne segments with rapid speed changes), using the generalised equations 2.7.13 (as taxi-in speed is not equal to zero). The engine power changes from final approach power at touchdown to a reverse thrust power setting Prev over a distance 0,1•sstop , then decreases to 10 % of the maximum available power over the remaining 90 percent of the stop distance. Up to the end of the runway (at s = -s RWY) aircraft speed remains constant.

NPD curves for reverse thrust are not at present included in the ANP database, and it is therefore necessary to rely on the conventional curves for modelling this effect. Typically the reverse thrust power Prev is around 20 % of the full power setting and this is recommended when no operational information is available. However, at a given power setting, reverse thrust tends to generate significantly more noise than forward thrust and an increment ΔL shall be applied to the NPD-derived event level, increasing from zero to a value ΔLrev (5 dB is recommended provisionally (***)) along 0,1•sstop and then falling linearly to zero along the remainder of the stop distance.

Segmentation of the initial climb and final approach segments

The segment-to-receiver geometry changes rapidly along the initial climb and final approach airborne segments, particularly with respect to observer locations to the side of the flight track, where the elevation angle (beta angle) also changes rapidly as the aircraft climbs or descends through these initial/final segments. Comparisons with very small segment calculations show that using a single (or a limited number of) climb or approach airborne segment(s) below a certain height (relative to the runway) results in a poor approximation of noise to the side of the flight track for integrated metrics. This is due to the application of a single lateral attenuation adjustment on each segment, corresponding to a single segment-specific value of the elevation angle, whereas the rapid change of this parameter results in significant variations of the lateral attenuation effect along each segment. Calculation accuracy is improved by sub-segmenting the initial climb and last approach airborne segments. The number of sub-segments and the length of each determine the lateral attenuation change “granularity” which will be accounted for. Noting the expression of total lateral attenuation for aircraft with fuselage-mounted engines, it can be shown that for a limiting change in lateral attenuation of 1,5 dB per sub-segment, the climb and approach airborne segments located below a height of 1 289,6 m (4 231 ft) above the runway should be sub-segmented based on the following set of height values:


z = {18,9, 41,5, 68,3, 102,1, 147,5, 214,9, 334,9, 609,6, 1 289,6} metres, or


z = {62, 136, 224, 335, 484, 705, 1 099, 2 000, 4 231} feet

For each original segment below 1 289,6 m (4 231 ft), the above heights are implemented by identifying which height in the set above is closest to the original endpoint height (for a climb segment) or start-point height (for an approach segment). The actual sub-segment heights, zi, would then be calculated using:


zi = ze [z’i / z’N] (i = k..N)



is the original segment endpoint height (climb) or start-point height (approach)


is the ith member of the set of height values listed above


is the closest height from the set of height values listed above to height ze


denotes the index of the first member of the set of height values for which the calculated zk is strictly greater than the endpoint height of the previous original climb segment or the start-point height of the next original approach segment to be sub-segmented.

In the specific case of an initial climb segment or last approach segment, k = 1, but in the more general case of airborne segments not connected to the runway, k will be greater than 1.

Example for an initial climb segment:

If the original segment endpoint height is ze = 304,8 m, then from the set of height values, 214,9 m < ze < 334,9 m and the closest height from the set to ze is z’7 = 334,9 m. The sub-segment endpoint heights are then computed by:


zi = 304,8 [z’i / 334,9] for i = 1 to 7

(noting that k =1 in that case, as this is an initial climb segment)

Thus z1 would be 17,2 m and z2 would be 37,8 m, etc.

Segmentation of airborne segments

For airborne segments where there is a significant speed change along a segment, this shall be subdivided as for the ground roll, namely

nseg = int (1 + |V 2 - V 1|/10)


where V1 and V2 are the segment start and end speeds respectively. The corresponding sub-segment parameters are calculated in a similar manner as for the takeoff ground roll, using equations 2.7.9 to 2.7.11.

Ground track

A ground track, whether a backbone track or a dispersed sub-track, is defined by a series of (x,y) co-ordinates in the ground plane (e.g. from radar information) or by a sequence of vectoring commands describing straight segments and circular arcs (turns of defined radius r and change of heading Δξ).

For segmentation modelling, an arc is represented by a sequence of straight segments fitted to sub-arcs. Although they do not appear explicitly in the ground-track segments, the banking of aircraft during turns influences their definition. Appendix B4 explains how to calculate bank angles during a steady turn but of course these are not actually applied or removed instantaneously. How to handle the transitions between straight and turning flight, or between one turn and an immediately sequential one, is not prescribed. As a rule, the details, which are left to the user (see Section 2.7.11), are likely to have a negligible effect on the final contours; the requirement is mainly to avoid sharp discontinuities at the ends of the turn and this can be achieved simply, for example, by inserting short transition segments over which the bank angle changes linearly with distance. Only in the special case that a particular turn is likely to have a dominating effect on the final contours would it be necessary to model the dynamics of the transition more realistically, to relate bank angle to particular aircraft types and to adopt appropriate roll rates. Here it is sufficient to state that the end sub-arcs Δξtrans in any turn are dictated by bank angle change requirements. The remainder of the arc with change of heading Δξ - 2·Δξtrans degrees is divided into nsub sub-arcs according to the equation:

nsub = int (1 + (Δξ – 2•Δξ trans ) / 10


where int(x) is a function that returns the integer part of x. Then the change of heading Δξ sub of each sub-arc is computed as

Δξ = (ξ-2•Δξ trans ) / nsub


where nsub needs to be large enough to ensure that Δξ sub ≤ 10 degrees. The segmentation of an arc (excluding the terminating transition sub-segments) is illustrated in Figure 2.7.h.2  (****).

Image 35
Figure 2.7.h.2 Construction of flight path segments dividing turn into segments of length Δs (upper view in horizontal plane, lower view in vertical plane) s

Once the ground track segments have been established in the x-y plane, the flight profile segments (in the s-z plane) are overlaid to produce the three-dimensional (x, y, z) track segments.

The ground track should always extend from the runway to beyond the extent of the calculation grid. This can be achieved, if necessary, by adding a straight segment of suitable length to the last segment of the ground track.

The total length of the flight profile, once merged with the ground track, must also extend from the runway to beyond the extent of the calculation grid. This can be achieved, if necessary, by adding an extra profile point:

to the end of a departure profile with speed and thrust values equal to those of the last departure profile point, and height extrapolated linearly from the last and penultimate profile points, or

to the beginning of an arrival profile with speed and thrust value equal to those of the first arrival profile point, and height extrapolated linearly back from the first and second profile points.

Segmentation adjustments of airborne segments

After the 3-D flight path segments have been derived according to the procedure described in Section 2.7.13, further segmentation adjustments may be necessary to remove flight path points which are too close together.

When adjacent points are within 10 metres of each other, and when the associated speeds and thrusts are the same, one of the points should be eliminated.

(*)  For this purpose the total length of the ground track should always exceed that of the flight profile. This can be achieved, if necessary, by adding straight segments of suitable length to the last segment of the ground track."

(**)  Even if engine power settings remain constant along a segment, propulsive force and acceleration can change due to variation of air density with height. However, for the purposes of noise modelling these changes are normally negligible."

(***)  This was recommended in the previous edition of ECAC Doc 29 but is still considered provisional pending the acquisition of further corroborative experimental data."

(****)  Defined in this simple way, the total length of the segmented path is slightly less than that of the circular path. However the consequent contour error is negligible if the angular increments are below 30°.’."


Section 2.7.16. ‘Determination of event levels from NPD-data’, is replaced by the following:

‘2.7.16    Determination of event levels from NPD-data

The principal source of aircraft noise data is the international Aircraft Noise and Performance (ANP) database. This tabulates Lmax and LE as functions of propagation distance d – for specific aircraft types, variants, flight configurations (approach, departure, flap settings), and power settings P. They relate to steady flight at specific reference speeds Vref along a notionally infinite, straight flight path (*).

How values of the independent variables P and d are specified is described later. In a single look-up, with input values P and d, the output values required are the baseline levels Lmax(P,d) and/or LE (P,d) (applicable to an infinite flight path). Unless values happen to be tabulated for P and/or d exactly, it will generally be necessary to estimate the required event noise level(s) by interpolation. A linear interpolation is used between tabulated power-settings, whereas a logarithmic interpolation is used between tabulated distances (see Figure 2.7.i).