(1)

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.’.

(2)

Section 2.2.1 is amended as follows:

(3)

Table 2.3.b is amended as follows:

(4)

Section 2.3.2 is amended as follows:

(d)

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 for - π/2< ψ <=0 is ΔLW,dir,ver,i = 0 (2.3.16)’

(5)

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

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.’.

(6)

Section 2.4.1 is amended as follows:

(7)

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.’.

(8)

Section 2.5.5 is amended as follows:

(9)

Section 2.5.6 is amended as follows:

(d)

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: (2.5.23)’

(e)	the Figure 2.5.d is replaced by the following:

(f)

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 , , and have an identical radius of curvature Γ defined by: Γ = max (1 000,8 d) (2.5.24) Where d is defined by the 3D distance between source and receiver of the unfolded path.’;

(g)

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: ‘ (2.5.28)’ 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. In the scenario presented in Figure 2.5.f, the path difference is: ‘ (2.5.29)’

(h)

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) (2.5.31) where — 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: — zr=zo,s; — Gpath is calculated between S and O; — In homogeneous conditions: in Equation (2.5.17), in Equation (2.5.18); — In favourable conditions: in Equation (2.5.17), 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) (2.5.32) where — 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, in Equation (2.5.17) and in Equation (2.5.18). — In favourable conditions, in Equation (2.5.17) and 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 ) ’’;

(i)

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: (2.5.33) (2.5.34) 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.’;

(k)

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. The sound power of the equivalent source is expressed by: (2.5.39) 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 With: LW the sound power of the real source ΔLgeo,n a correction term for spherical divergence ΔLdif,n a correction term for diffraction by the top of the obstacle ΔLabs,n a correction term for the absorption at the inner side of the obstacle ΔLref,n a correction term for reflection from the railway vehicle body ΔLretrodif,n a correction term for the finite height of the obstacle as a reflector The correction for spherical divergence is given by (2.5.40) (2.5.41) The correction for diffraction by the top of the obstacle is given by: (2.5.42) ΔLdif,n = D0 - Dn (2.5.42) 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|) (2.5.43) The correction for absorption on the inner side of the obstacle is given by: ΔLabs,n = 10•n•lg (1-α) (2.5.44) The correction for reflection from the railway vehicle body is given by: ΔLref,n = 10•n•lg (Cref) (2.5.45) 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: (2.5.46) 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 (2.5.47) (2.5.48)’

(10)

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.’.

(11)

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

‘ Lateral track dispersion ’.

(12)

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.’.

(13)

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:

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)	(2.7.3)
	(2.7.4)
ε = ε1 + f · (ε2 - ε1)	(2.7.5)
	(2.7.6)

where

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

and hence the change of velocity along a segment is

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

(2.7.10)

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

(2.7.11)

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):

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

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.

(2.7.13)

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

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).

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:

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:

where:

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:

(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

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:

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

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  (****).

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:

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°.’."

(14)

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).

If Pi and Pi+ 1 are engine power values for which noise level versus distance data are tabulated, the noise level L(P) at a given distance for intermediate power P, between Pi and Pi+ 1 ,is given by:

(2.7.19)

If, at any power setting, di and di+ 1 are distances for which noise data are tabulated, the noise level L(d) for an intermediate distance d, between di and di+ 1 is given by

(2.7.20)

By using equations (2.7.19) and (2.7.20), a noise level L(P,d) can be obtained for any power setting P and any distance d that is within the envelope of the NPD data base.

For distances d that lie outside the NPD envelope, equation 2.7.20 is used to extrapolate from the last two values, namely inwards from L(d1) and L(d2) or outwards from L(dI-1) and L(dI) where I is the total number of NPD points on the curve. Thus

Inwards:

(2.7.21)

Outwards:

(2.7.22)

As, at short distances d, noise levels increase very rapidly with decreasing propagation distance, it is recommended that a lower limit of 30 m be imposed on d, namely d = max(d, 30 m).

Impedance adjustment of standard NPD data

The NPD data provided in the ANP database are normalized to reference atmospheric conditions (temperature of 25 °C and pressure of 101,325 kPa). Before applying the interpolation/extrapolation method previously described, an acoustic impedance adjustment shall be applied to these standard NPD data.

Acoustic impedance is related to the propagation of sound waves in an acoustic medium, and is defined as the product of the density of air and the speed of sound. For a given sound intensity (power per unit area) perceived at a specific distance from the source, the associated sound pressure (used to define SEL and LAmax metrics) depends on the acoustic impedance of the air at the measurement location. It is a function of temperature, atmospheric pressure (and indirectly altitude). There is therefore a need to adjust the standard NPD data of the ANP database to account for the actual temperature and pressure conditions at the receiver point, which are generally different from the normalized conditions of the ANP data.

The impedance adjustment to be applied to the standard NPD levels is expressed as follows:

(2.7.23)

where:

Impedance ρ·c is calculated as follows:

(2.7.24)

The acoustic impedance adjustment is usually less than a few tenths of one dB. In particular, it should be noted that under the standard atmospheric conditions (p0 = 101,325 kPa and T0 = 15,0 °C), the impedance adjustment is less than 0,1 dB (0,074 dB). However, when there is a significant variation in temperature and atmospheric pressure relative to the reference atmospheric conditions of the NPD data, the adjustment can be more substantial.

(*)  Although the notion of an infinitely long flight path is important to the definition of event sound exposure level LE , it has less relevance in the case of event maximum level Lmax which is governed by the noise emitted by the aircraft when at a particular position at or near its closest point of approach to the observer. For modelling purposes the NPD distance parameter is taken to be the minimum distance between the observer and segment.’."

(15)

In Section 2.7.18. ‘Flight path segment parameters’, the paragraph under the headings ‘Segment power P’ is replaced by the following:

‘ Segment power P

The tabulated NPD data describe the noise of an aircraft in steady straight flight on an infinite flight path, that is to say, at constant engine power P. The recommended methodology breaks actual flight paths, along which speed and direction vary, into a number of finite segments, each of which is then taken to be part of a uniform, infinite flight path for which the NPD data are valid. But the methodology provides for changes of power along the length of a segment; it is taken to change quadratically with distance from P1 at its start to P2 at its end. It is therefore necessary to define an equivalent steady segment value P. This is taken to be the value at the point on the segment that is closest to the observer. If the observer is alongside the segment (Figure 2.7.k) it is obtained by interpolation as given by equation 2.7.8 between the end values, namely

(2.7.31)

If the observer is behind or ahead of the segment, it is that at the nearest end point, P1 or P2 .’.

(16)

Section 2.7.19 is amended as follows

(a)

in the paragraph under the headings ‘The duration correction DV (Exposure levels LE only)’ until and including the formula 2.7.34 is replaced by the following: ‘ The duration correction ΔV (Exposure levels LE only) This correction (*) accounts for a change in exposure levels if the actual segment groundspeed is different to the aircraft reference speed Vref to which the basic NPD-data relate. Like engine power, speed varies along the flight path segment (from VT1 to VT2, which are the speeds output from Appendix B or from a previously pre-calculated flight profile). For airborne segments, Vseg is the segment speed at the closest point of approach, S, interpolated between the segment end-point values assuming it varies quadratically with time; namely if the observer is alongside the segment: (2.7.32) (*)  This is known as the duration correction because it makes allowance for the effects of aircraft speed on the duration of the sound event – implementing the simple assumption that, other things being equal, duration, and thus received event sound energy, is inversely proportional to source velocity.’;"

(e)

the text under the Figure 2.7.p is replaced by the following: ‘To calculate the lateral attenuation using equation (2.7.40) (where β is measured in a vertical plane), an extended level flight path is recommended. An extended level flight path is defined in the vertical plane through S1S2 and with the same perpendicular slant distance dp from the observer. This is visualised by rotating the triangle ORS, and its attached flight path about OR (see Figure 2.7p) through angle γ thus forming the triangle ORS’. The elevation angle of this equivalent level path (now in a vertical plane) is β = tan-1(h/ℓ) (ℓ remains unchanged). In this case, for an observer alongside, angle β and the resulting lateral attenuation Λ(β, ℓ) are the same for LE and Lmax metrics. Figure 2.7.r illustrates the situation when the observer point O lies behind the finite segment, not alongside. Here the segment is observed as a more distant part of an infinite path; a perpendicular can only be drawn to point Sp on its extension. The triangle OS1S2 accords with Figure 2.7.j which defines the segment correction Δ F . But in this case the parameters for lateral directivity and attenuation are less obvious. For maximum level metrics, the NPD distance parameter is taken as the shortest distance to the segment, namely d = d 1. For exposure level metrics, it is the shortest distance dp from O to Sp on the extended flight path; namely the level interpolated from the NPD table is LE ∞ (P 1, dp ). The geometrical parameters for lateral attenuation also differ for maximum and exposure level calculations. For maximum level metrics the adjustment Λ(β,ℓ) is given by equation 2.7.40 with β = β1 = sin-1 (z 1 /d 1) and where β1 and d1 are defined by the triangle OC1S1 in the vertical plane through O and S1 . When calculating the lateral attenuation for airborne segments only and exposure level metrics, ℓ remains the shortest lateral displacement from the segment extension (OC). But to define an appropriate value of β it is again necessary to visualise an (infinite) equivalent level flight path of which the segment can be considered part. This is drawn through S1', height h above the surface, where h is equal to the length of RS1 the perpendicular from the ground track to the segment. This is equivalent to rotating the actual extended flight path through angle γ about point R (see Figure 2.7.q). Insofar as R is on the perpendicular to S1 , the point on the segment that is closest to O, the construction of the equivalent level path is the same as when O is alongside the segment. The closest point of approach of the equivalent level path to the observer O is at S’, slant distance d, so that the triangle OCS’ so formed in the vertical plane then defines the elevation angle β = cos -1(ℓ/d). Although this transformation might seem rather convoluted, it should be noted that the basic source geometry (defined by d1 , d2 and φ) remains untouched, the sound travelling from the segment towards the observer is simply what it would be if the entire flight along the infinitely extended inclined segment (of which for modelling purposes the segment forms part) were at constant speed V and power P1 . The lateral attenuation of sound from the segment received by the observer, on the other hand, is related not to β p , the elevation angle of the extended path, but to β, that of the equivalent level path. Remembering that, as conceived for modelling purposes, the engine installation effect Δ I is two-dimensional, the defining depression angle φ is still measured laterally from the aircraft wing plane (the baseline event level is still that generated by the aircraft traversing the infinite flight path represented by the extended segment). Thus the depression angle is determined at the closest point of approach, namely φ = β p  – ε where β p is angle SpOC. The case of an observer ahead of the segment is not described separately; it is evident that this is essentially the same as the case of the observer behind. However, for exposure level metrics where observer locations are behind ground segments during the takeoff roll and ahead of ground segments during the landing roll, the value of β becomes the same as that for maximum level metrics. For locations behind takeoff roll segments:   β = β 1 = sin-1(z 1/d 1) and For locations ahead of landing roll segments:   β = β 2 = sin-1(z 2/d 2) and The rationale for using these particular expressions is related to the application of the start-of-roll directivity function behind takeoff roll segments and a semi-circular directivity assumption ahead of landing roll segments. The finite segment correction Δ F (Exposure levels LE only) The adjusted baseline noise exposure level relates to an aircraft in continuous, straight, steady level flight (albeit with a bank angle ε that is inconsistent with straight flight). Applying the (negative) finite segment correction Δ F = 10•lg(F), where F is the energy fraction, further adjusts the level to what it would be if the aircraft traversed the finite segment only (or were completely silent for the remainder of the infinite flight path). The energy fraction term accounts for the pronounced longitudinal directivity of aircraft noise and the angle subtended by the segment at the observer position. Although the processes that cause the directionality are very complex, studies have shown that the resulting contours are quite insensitive to the precise directional characteristics assumed. The expression for Δ F below is based on a fourth-power 90-degree dipole model of sound radiation. It is assumed to be unaffected by lateral directivity and attenuation. How this correction is derived is described in detail in Appendix E. The energy fraction F is a function of the “view” triangle OS1S2 defined in Figures 2.7.j to 2.7.l such that: (2.7.45) With ; ; ; where dλ is known as the “scaled distance” (see Appendix E) and Vref = 270,05 ft/s (for the 160 knots reference speed). Note that Lmax(P, dp) is the maximum level, from NPD data, for perpendicular distance dp , NOT the segment Lmax .It is advised to apply a lower limit of -150 dB to Δ F. In the particular case of observer locations behind every takeoff ground-roll segment, a reduced form of the noise fraction expressed in Equation 2.7.45 is used, which corresponds to the specific case of q = 0. This is denoted where “d” clarifies its use for departure operations, and is computed as: (2.7.46.a) where α2 = λ / dλ. This particular form of the noise fraction is used in conjunction with the start-of-roll directivity function, whose application method is further explained in the section below. In the particular case of observer locations ahead of every landing ground-roll segment, a reduced form of the noise fraction expressed in equation 2.7.45 is used, which corresponds to the specific case of q = λ. This is denoted Δ’F,a where “a” clarifies its use for arrival operations, and is computed as: (2.7.46.b) where α1 = -λ / dλ. The use of this form, without the application of any further horizontal directivity adjustment (unlike the case of locations behind takeoff ground-roll segments – see section on start-of-roll directivity), implicitly assumes a semi-circular horizontal directivity ahead of landing ground roll segments. The start-of-roll directivity function Δ SOR The noise of aircraft – especially jet aircraft equipped with lower by-pass ratio engines – exhibits a lobed radiation pattern in the rearward arc, which is characteristic of jet exhaust noise. This pattern is the more pronounced the higher the jet velocity and the lower the aircraft speed. This is of special significance for observer locations behind the start of roll, where both conditions are fulfilled. This effect is taken into account by a directivity function Δ SOR . The function Δ SOR has been derived from several noise measurement campaigns using microphones adequately positioned behind and on the side of the SOR of departing jet aircraft. Figure 2.7.r shows the relevant geometry. The azimuth angle Ψ between the aircraft longitudinal axis and the vector to the observer is defined by (2.7.47) The relative distance q is negative (see Figure 2.7.j) so that Ψ ranges from 90° relative to the aircraft forward heading, to 180° in the reverse direction. The function Δ SOR represents the variation of the overall noise emanating from the takeoff ground roll measured behind the start of roll, relatively to the overall noise from takeoff ground roll measured on the side of the SOR, at the same distance: LTGR (dSOR , ψ) = LTGR (dSOR ,90°) +Δ SOR (dSOR ,ψ) (2.7.48) where LTGR (dSOR ,90°) is the overall takeoff ground roll noise level at the point distance dSOR to the side of the SOR. ΔSOR is implemented as an adjustment to the noise level from one flight path segment (e.g. Lmax,seg or LE,seg), as described in equation 2.7.28. The SOR directivity function, in decibels, for turbofan-powered jet aircraft is given by the following equation:   For 90° ≤ Ψ < 180° then: (2.7.49) The SOR directivity function, in decibels, for turboprop-powered aircraft is given by the following equation:   For 90° ≤ Ψ < 180° then: (2.7.50) If the distance dSOR exceeds the normalising distance dSOR,0 , the directivity correction is multiplied by a correction factor to account for the fact that the directivity becomes less pronounced for greater distances from the aircraft; namely if dSOR ≤ dSOR,0 (2.7.51) if dSOR > dSOR,0 (2.7.52) The normalising distance dSOR,0 equals 762 m (2 500 ft). The Δ SOR function described above mostly captures the pronounced directivity effect of the initial portion of the takeoff roll at locations behind the SOR (because it is the closest to the receivers, with the highest jet velocity to aircraft speed ratio). However, the use of the hence established Δ SOR is “generalised” to positions behind each individual takeoff ground roll segment, so not only behind the start-of-roll point (in the case of takeoff). The established Δ SOR is not applied to positions ahead of individual takeoff ground roll segments, nor is it applied to positions behind or ahead of individual landing ground roll segments. The parameters dSOR and Ψ are calculated relative to the start of each individual ground roll segment. The event level LSEG for a location behind a given takeoff ground-roll segment is calculated to comply with the formalism of the Δ SOR function: it is essentially calculated for the reference point located on the side of the start point of the segment, at the same distance dSOR as the actual point, and is further adjusted with Δ SOR to obtain the event level at the actual point. Note: Formulas (2.7.53), (2.7.54) and (2.7.55) were removed in the latest amendment of this Annex. ’.

(17)

Section 2.8 is replaced by the following:

‘2.8   Exposure to noise

Determination of the area exposed to noise

The assessment of the area exposed to noise is based on noise assessment points at 4 m ± 0,2 above the ground, corresponding to the receiver points as defined in 2.5, 2.6 and 2.7, calculated on a grid for individual sources.

Grid points that are located inside buildings shall be assigned a noise level result by assigning the quietest nearby noise receiver points outside buildings, except for aircraft noise where the calculation is performed without considering the presence of buildings and in which case the noise receiver point falling within a building is directly used.

Depending on the grid resolution, the corresponding area is assigned to each calculation point in the grid. For example, with a 10 m × 10 m grid, each assessment point represents an area of 100 square metres that is exposed to the calculated noise level.

Assigning noise assessment points to buildings not containing dwellings

The assessment of the exposure of buildings not containing dwellings such as schools and hospitals to noise is based on noise assessment points at 4 ± 0,2 m above the ground, corresponding to the receiver points as defined in 2.5, 2.6 and 2.7

For the assessment of buildings not containing dwellings and exposed to aircraft noise, each building is associated to the noisiest noise receiver point falling within the building itself or, if not present, on the grid surrounding the building.

For the assessment of buildings not containing dwellings and exposed to land-based noise sources, receiver points are placed at approximately 0,1 m in front of building façades. Reflections from the façade being considered shall be excluded from the calculation. The building is then associated to the noisiest receiver point on its façades.

Determination of the dwellings and people living in dwellings exposed to noise

For the assessment of the noise exposure of dwellings and the exposure of people living in dwellings, only residential buildings shall be considered. No dwellings or people shall be assigned to other buildings without residential use such as buildings exclusively used as schools, hospitals, office buildings or factories. The assignment of the dwellings, and people living in dwellings, to the residential buildings shall be based on the latest official data (depending on the Member State’s relevant regulations).

The number of dwellings, and people living in dwellings, in residential buildings are important intermediate parameters for the estimation of the exposure to noise. Unfortunately, data on these parameters is not always available. Below, it is specified how these parameters can be derived from data more readily available.

Symbols used in the following are:

BA = base area of the building

DFS = dwelling floor space

DUFS = dwelling unit floor space

H = height of the building

FSI = dwelling floor space per person living in dwellings

Dw = number of dwellings

Inh = number of people living in dwellings

NF = number of floors

V = volume of residential buildings

For the calculation of the number of dwellings, and people living in dwellings, either the following Case 1 procedure or the Case 2 procedure shall be used, depending on the availability of data.

Case 1: the data on the number of dwellings and people living in dwellings is available

1A:

The number of people living in dwellings is known or has been estimated on the basis of the number of dwelling units. In this case the number of people living in dwellings for a building is the sum of the number of people living in all dwelling units in the building:

(2.8.1)

1B:

The number of dwellings or people living in dwellings is only known for entities larger than a building, e.g., enumeration areas, city blocks, districts or even an entire municipality. In this case the number of dwellings, and people living in dwellings, in a building is estimated based on the volume of the building:

(2.8.2a)

(2.8.2b)

The index “total” here refers to the respective entity considered. The volume of the building is the product of its base area and its height:

If the height of the building is not known, it shall be estimated based on the number of floors NFbuilding , assuming an average height per floor of 3 m:

If the number of floors is also not known, a default value for the number of floors, representative of the district or the borough, shall be used. The total volume of residential buildings in the entity considered Vtotal is calculated as the sum of the volumes of all residential buildings in the entity:

(2.8.5)

(2.8.5)

Case 2: no data on the number of people living in dwellings is available

In this case, the number of people living in dwellings is estimated based on the average dwelling floor space per person living in dwellings FSI. If this parameter is not known, a default value shall be used.

2A:

The dwelling floor space is known on the basis of dwelling units.

In this case the number of people living in each dwelling unit is estimated as follows:

(2.8.6)

The total number of people living in dwellings for the building can now be estimated as in Case 1A.

2B:

The dwelling floor space is known for the entire building, that is to say, the sum of the dwelling floor spaces of all dwelling units in the building is known.

In this case the number of people living in dwellings is estimated as follows:

(2.8.7)

2C:

The dwelling floor space is known only for entities larger than a building, e.g., enumeration areas, city blocks, districts or even an entire municipality.

In this case the number of people living in dwellings for a building is estimated based on the volume of the building as described in Case 1B with the total number of people living in dwellings estimated as follows:

(2.8.8)

2D:

The dwelling floor space is unknown.

In this case the number of people living in dwellings for a building is estimated as described in Case 2B with the dwelling floor space estimated as follows:

(2.8.9)

The factor 0,8 is the conversion factor gross floor area → dwelling floor space. If a different factor is known to be representative of the area it shall be used instead and clearly documented. If the number of floors of the building is not known, it shall be estimated based on the height of the building, Hbuilding , which typically results in a non-integer number of floors:

(2.8.10)

If neither the height of the building nor the number of floors is known, a default value for the number of floors, representative of the district or the borough, shall be used.

Assigning noise assessment points to dwellings and people living in dwellings

The assessment of the exposure of dwellings, and people living in dwellings, to noise is based on noise assessment points at 4 ± 0,2 m above the ground, corresponding to the receiver points as defined in 2.5, 2.6 and 2.7.

For the calculation of the number of dwellings, and people living in dwellings for aircraft noise, all dwellings, and people living in dwellings, within a building are associated to the noisiest noise receiver point falling within the building itself or, if not present, on the grid surrounding the building.

For the calculation of the number of dwellings, and people living in dwellings for land-based noise sources, receiver points are placed at approximately 0,1 m in front of building façades of residential buildings. Reflections from the façade being considered shall be excluded from the calculation. Either the following Case 1 procedure or the Case 2 procedure shall be used to locate the receiver points.

Case 1: façades split up in regular intervals on each façade

Case 2: façades split up at set distance from start of polygon

Assigning dwellings and people living in dwellings to receiver points

Where information on the location of dwellings within building footprints is available, that dwelling and the people living in that dwelling are assigned to the receiver point at the most exposed façade of that dwelling. For example, for detached houses, for semi-detached and terrace houses, or apartment buildings, where the internal division of the building is known, or for buildings with a floor size that indicates a single dwelling per floor level, or for buildings with a floor size and height that indicates a single dwelling per building.

Where no information on the location of dwellings within building footprints as explained above is available, one of the two following methods shall be used, as appropriate, on a building by building basis to estimate the exposure to noise of the dwellings and people in dwellings within the buildings.

(*)  The medium value is the value separating the higher half (50 %) from the lower half (50 %) of a data set."

(**)  The lower half of the data asset may be assimilated with the presence of relatively calm façades. In case it is known in advance, e.g. based on the location of buildings relative to the dominant noise sources, which receiver locations will give way to the highest / lowest noise levels, there is no need to calculate noise for the lower half.’."

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Appendix D is amended as follows:

(b)

in the third sub-paragraph under Table D-1, points 2 and 3 are replaced by the following: ‘2. Next the corrected spectrum is adjusted to each of the ten standard NPD distances di using attenuation rates for both (i) the SAE AIR-1845 atmosphere; and (ii) the user-specified atmosphere (based on SAE ARP-5534). (i) For the SAE AIR-1845 atmosphere: Ln,ref (di ) = Ln (dref )-20.lg(di/dref ) - α n,ref · di (D-2) (ii) For the user-specified atmosphere: Ln, 5534(T,RH,di ) = Ln (dref ) - 20.lg(di/dref ) - α n, 5534(T,RH) di (D-3) where α n,5534 is the coefficient of atmospheric absorption for the frequency band n (expressed in dB/m) calculated using SAE ARP-5534 with temperature T, and relative humidity RH. 3. At each NPD distance di the two spectra are A-weighted and decibel-summed to determine the resulting A-weighted levels LA,5534 and LA,ref – which are then subtracted arithmetically: (D-4)’

(19)

Appendix F is amended as follows:

(20)

Appendix G is amended as follows: