02002L0049 — EN — 02.07.2015 — 002.002

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►B 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 (OJ L 189 18.7.2002, p. 12)

Amended by:





Corrected by:









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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







Article 1

Objectives

1. The aim of this Directive shall be to define a common approach intended to avoid, prevent or reduce on a prioritised basis the harmful effects, including annoyance, due to exposure to environmental noise. To that end the following actions shall be implemented progressively:

(a) the determination of exposure to environmental noise, through noise mapping, by methods of assessment common to the Member States;

(b) ensuring that information on environmental noise and its effects is made available to the public;

(c) adoption of action plans by the Member States, based upon noise-mapping results, with a view to preventing and reducing environmental noise where necessary and particularly where exposure levels can induce harmful effects on human health and to preserving environmental noise quality where it is good.

2. This Directive shall also aim at providing a basis for developing Community measures to reduce noise emitted by the major sources, in particular road and rail vehicles and infrastructure, aircraft, outdoor and industrial equipment and mobile machinery. To this end, the Commission shall submit to the European Parliament and the Council, no later than 18 July 2006, appropriate legislative proposals. Those proposals should take into account the results of the report referred to in Article 10(1).

Article 2

Scope

1. This Directive shall apply to environmental noise to which humans are exposed in particular in built-up areas, in public parks or other quiet areas in an agglomeration, in quiet areas in open country, near schools, hospitals and other noise-sensitive buildings and areas.

2. This Directive shall not apply to noise that is caused by the exposed person himself, noise from domestic activities, noise created by neighbours, noise at work places or noise inside means of transport or due to military activities in military areas.

Article 3

Definitions

For the purposes of this Directive:

(a) ‘environmental noise’ shall mean unwanted or harmful outdoor sound created by human activities, including noise emitted by means of transport, road traffic, rail traffic, air traffic, and from sites of industrial activity such as those defined in Annex I to Council Directive 96/61/EC of 24 September 1996 concerning integrated pollution prevention and control ( 1 );

(b) ‘harmful effects’ shall mean negative effects on human health;

(c) ‘annoyance’ shall mean the degree of community noise annoyance as determined by means of field surveys;

(d) ‘noise indicator’ shall mean a physical scale for the description of environmental noise, which has a relationship with a harmful effect;

(e) ‘assessment’ shall mean any method used to calculate, predict, estimate or measure the value of a noise indicator or the related harmful effects;

(f) ‘Lden’ (day-evening-night noise indicator) shall mean the noise indicator for overall annoyance, as further defined in Annex I;

(g) ‘Lday’ (day-noise indicator) shall mean the noise indicator for annoyance during the day period, as further defined in Annex I;

(h) ‘Levening’ (evening-noise indicator) shall mean the noise indicator for annoyance during the evening period, as further defined in Annex I;

(i) ‘Lnight’ (night-time noise indicator) shall mean the noise indicator for sleep disturbance, as further defined in Annex I;

(j) ‘dose-effect relation’ shall mean the relationship between the value of a noise indicator and a harmful effect;

(k) ‘agglomeration’ shall mean part of a territory, delimited by the Member State, having a population in excess of 100 000 persons and a population density such that the Member State considers it to be an urbanised area;

(l) ‘quiet area in an agglomeration’ shall mean an area, delimited by the competent authority, for instance which is not exposed to a value of Lden or of another appropriate noise indicator greater than a certain value set by the Member State, from any noise source;

(m) ‘quiet area in open country’ shall mean an area, delimited by the competent authority, that is undisturbed by noise from traffic, industry or recreational activities;

(n) ‘major road’ shall mean a regional, national or international road, designated by the Member State, which has more than three million vehicle passages a year;

(o) ‘major railway’ shall mean a railway, designated by the Member State, which has more than 30 000 train passages per year;

(p) ‘major airport’ shall mean a civil airport, designated by the Member State, which has more than 50 000 movements per year (a movement being a take-off or a landing), excluding those purely for training purposes on light aircraft;

(q) ‘noise mapping’ shall mean the presentation of data on an existing or predicted noise situation in terms of a noise indicator, indicating breaches of any relevant limit value in force, the number of people affected in a certain area, or the number of dwellings exposed to certain values of a noise indicator in a certain area;

(r) ‘strategic noise map’ shall mean a map designed for the global assessment of noise exposure in a given area due to different noise sources or for overall predictions for such an area;

(s) ‘limit value’ shall mean a value of Lden or Lnight, and where appropriate Lday and Levening, as determined by the Member State, the exceeding of which causes competent authorities to consider or enforce mitigation measures; limit values may be different for different types of noise (road-, rail-, air-traffic noise, industrial noise, etc.), different surroundings and different noise sensitiveness of the populations; they may also be different for existing situations and for new situations (where there is a change in the situation regarding the noise source or the use of the surrounding);

(t) ‘action plans’ shall mean plans designed to manage noise issues and effects, including noise reduction if necessary;

(u) ‘acoustical planning’ shall mean controlling future noise by planned measures, such as land-use planning, systems engineering for traffic, traffic planning, abatement by sound-insulation measures and noise control of sources;

(v) ‘the public’ shall mean one or more natural or legal persons and, in accordance with national legislation or practice, their associations, organisations or groups.

Article 4

Implementation and responsibilities

1. Member States shall designate at the appropriate levels the competent authorities and bodies responsible for implementing this Directive, including the authorities responsible for:

(a) making and, where relevant, approving noise maps and action plans for agglomerations, major roads, major railways and major airports;

(b) collecting noise maps and action plans.

2. The Member States shall make the information referred to in paragraph 1 available to the Commission and to the public no later than 18 July 2005.

Article 5

Noise indicators and their application

1. Member States shall apply the noise indicators Lden and Lnight as referred to in Annex I for the preparation and revision of strategic noise mapping in accordance with Article 7.

Until the use of common assessment methods for the determination of Lden and Lnight is made obligatory, existing national noise indicators and related data may be used by Member States for this purpose and should be converted into the indicators mentioned above. These data must not be more than three years old.

2. Member States may use supplementary noise indicators for special cases such as those listed in Annex I(3).

3. For acoustical planning and noise zoning, Member States may use other noise indicators than Lden and Lnight.

4. No later than 18 July 2005, Member States shall communicate information to the Commission on any relevant limit values in force within their territories or under preparation, expressed in terms of Lden and Lnight and where appropriate, Lday and Levening, for road-traffic noise, rail-traffic noise, aircraft noise around airports and noise on industrial activity sites, together with explanations about the implementation of the limit values.

Article 6

Assessment methods

1. The values of Lden and Lnight shall be determined by means of the assessment methods defined in Annex II.

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2. The Commission shall, through a revision of Annex II, establish common assessment methods for the determination of Lden and Lnight. Those measures, designed to amend non-essential elements of this Directive, shall be adopted in accordance with the regulatory procedure with scrutiny referred to in Article 13(3). Until those methods are adopted, Member States may use assessment methods adapted in accordance with Annex II and based upon the methods laid down in their own legislation. In such case, the Member States must demonstrate that those methods give equivalent results to the results obtained with the methods set out in paragraph 2(2) of Annex II.

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3. Harmful effects may be assessed by means of the dose-effect relations referred to in Annex III.

Article 7

Strategic noise mapping

1. Member States shall ensure that no later than 30 June 2007 strategic noise maps showing the situation in the preceding calendar year have been made and, where relevant, approved by the competent authorities, for all agglomerations with more than 250 000 inhabitants and for all major roads which have more than six million vehicle passages a year, major railways which have more than 60 000 train passages per year and major airports within their territories.

No later than 30 June 2005, and thereafter every five years, Member States shall inform the Commission of the major roads which have more than six million vehicle passages a year, major railways which have more than 60 000 train passages per year, major airports and the agglomerations with more than 250 000 inhabitants within their territories.

2. Member States shall adopt the measures necessary to ensure that no later than 30 June 2012, and thereafter every five years, strategic noise maps showing the situation in the preceding calendar year have been made and, where relevant, approved by the competent authorities for all agglomerations and for all major roads and major railways within their territories.

No later than 31 December 2008, Member States shall inform the Commission of all the agglomerations and of all the major roads and major railways within their territories.

3. The strategic noise maps shall satisfy the minimum requirements laid down in Annex IV.

4. Neighbouring Member States shall cooperate on strategic noise mapping near borders.

5. The strategic noise maps shall be reviewed, and revised if necessary, at least every five years after the date of their preparation.

Article 8

Action plans

1. Member States shall ensure that no later than 18 July 2008 the competent authorities have drawn up action plans designed to manage, within their territories, noise issues and effects, including noise reduction if necessary for:

(a) places near the major roads which have more than six million vehicle passages a year, major railways which have more than 60 000 train passages per year and major airports;

(b) agglomerations with more than 250 000 inhabitants. Such plans shall also aim to protect quiet areas against an increase in noise.

The measures within the plans are at the discretion of the competent authorities, but should notably address priorities which may be identified by the exceeding of any relevant limit value or by other criteria chosen by the Member States and apply in particular to the most important areas as established by strategic noise mapping.

2. Member States shall ensure that, no later than 18 July 2013, the competent authorities have drawn up action plans notably to address priorities which may be identified by the exceeding of any relevant limit value or by other criteria chosen by the Member States for the agglomerations and for the major roads as well as the major railways within their territories.

3. Member States shall inform the Commission of the other relevant criteria referred to in paragraphs 1 and 2.

4. The action plans shall meet the minimum requirements of Annex V.

5. The action plans shall be reviewed, and revised if necessary, when a major development occurs affecting the existing noise situation, and at least every five years after the date of their approval.

6. Neighbouring Member States shall cooperate on the action plans for border regions.

7. Member States shall ensure that the public is consulted about proposals for action plans, given early and effective opportunities to participate in the preparation and review of the action plans, that the results of that participation are taken into account and that the public is informed on the decisions taken. Reasonable time-frames shall be provided allowing sufficient time for each stage of public participation.

If the obligation to carry out a public participation procedure arises simultaneously from this Directive and any other Community legislation, Member States may provide for joint procedures in order to avoid duplication.

Article 9

Information to the public

1. Member States shall ensure that the strategic noise maps they have made, and where appropriate adopted, and the action plans they have drawn up are made available and disseminated to the public in accordance with relevant Community legislation, in particular Council Directive 90/313/EEC of 7 June 1990 on the freedom of access to information on the environment ( 2 ), and in conformity with Annexes IV and V to this Directive, including by means of available information technologies.

2. This information shall be clear, comprehensible and accessible. A summary setting out the most important points shall be provided.

Article 10

Collection and publication of data by Member States and the Commission

1. No later than 18 January 2004, the Commission will submit a report to the European Parliament and the Council containing a review of existing Community measures relating to sources of environmental noise.

2. The Member States shall ensure that the information from strategic noise maps and summaries of the action plans as referred to in Annex VI are sent to the Commission within six months of the dates laid down in Articles 7 and 8 respectively.

3. The Commission shall set up a database of information on strategic noise maps in order to facilitate the compilation of the report referred to in Article 11 and other technical and informative work.

4. Every five years the Commission shall publish a summary report of data from strategic noise maps and action plans. The first report shall be submitted by 18 July 2009.

Article 11

Review and reporting

1. No later than 18 July 2009, the Commission shall submit to the European Parliament and the Council a report on the implementation of this Directive.

2. That report shall in particular assess the need for further Community actions on environmental noise and, if appropriate, propose implementing strategies on aspects such as:

(a) long-term and medium-term goals for the reduction of the number of persons harmfully affected by environmental noise, taking particularly into account the different climates and different cultures;

(b) additional measures for a reduction of the environmental noise emitted by specific sources, in particular outdoor equipment, means and infrastructures of transport and certain categories of industrial activity, building on those measures already implemented or under discussion for adoption;

(c) the protection of quiet areas in open country.

3. The report shall include a review of the acoustic environment quality in the Community based on the data referred to in Article 10 and shall take account of scientific and technical progress and any other relevant information. The reduction of harmful effects and the cost-effectiveness ratio shall be the main criteria for the selection of the strategies and measures proposed.

4. When the Commission has received the first set of strategic noise maps, it shall reconsider:

— the possibility for a 1,5 metre measurement height in Annex I, paragraph 1, in respect of areas having houses of one storey,

— the lower limit for the estimated number of people exposed to different bands of Lden and Lnight in Annex VI.

5. The report shall be reviewed every five years or more often if appropriate. It shall contain an assessment of the implementation of this Directive.

6. The report shall, if appropriate, be accompanied by proposals for the amendment of this Directive.

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Article 12

Adaptation to technical and scientific progress

The Commission shall adapt point 3 of Annex I and Annexes II and III to this Directive to technical and scientific progress. Those measures, designed to amend non-essential elements of this Directive, shall be adopted in accordance with the regulatory procedure with scrutiny referred to in Article 13(3).

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Article 13

Committee

1. The Commission shall be assisted by the committee set up by Article 18 of Directive 2000/14/EC.

2. Where reference is made to this paragraph, Articles 5 and 7 of Decision 1999/468/EC shall apply, having regard to the provisions of Article 8 thereof.

The period laid down in Article 5(6) of Decision 1999/468/EC shall be set at three months.

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3. Where reference is made to this paragraph, Article 5a(1) to (4) and Article 7 of Decision 1999/468/EC shall apply, having regard to the provisions of Article 8 thereof.

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Article 14

Transposition

1. Member States shall bring into force the laws, regulations and administrative provisions necessary to comply with this Directive no later than 18 July 2004. They shall inform the Commission thereof.

When the Member States adopt these measures, they shall contain a reference to this Directive or shall be accompanied by such a reference on the occasion of their official publication. The methods of making such a reference shall be laid down by the Member States.

2. The Member States shall communicate to the Commission the texts of the provisions of national law that they adopt in the field governed by this Directive.

Article 15

Entry into force

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

Article 16

Addressees

This Directive is addressed to the Member States.









ANNEX I

NOISE INDICATORS

referred to in Article 5

1. Definition of the day-evening-night level Lden

The day-evening-night level Lden in decibels (dB) is defined by the following formula:

in which:

— Lday is the A-weighted long-term average sound level as defined in ISO 1996-2: 1987, determined over all the day periods of a year,

— Levening is the A-weighted long-term average sound level as defined in ISO 1996-2: 1987, determined over all the evening periods of a year,

— Lnight is the A-weighted long-term average sound level as defined in ISO 1996-2: 1987, determined over all the night periods of a year;

in which:

— the day is 12 hours, the evening four hours and the night eight hours. The Member States may shorten the evening period by one or two hours and lengthen the day and/or the night period accordingly, provided that this choice is the same for all the sources and that they provide the Commission with information on any systematic difference from the default option,

— the start of the day (and consequently the start of the evening and the start of the night) shall be chosen by the Member State (that choice shall be the same for noise from all sources); the default values are 07.00 to 19.00, 19.00 to 23.00 and 23.00 to 07.00 local time,

— a year is a relevant year as regards the emission of sound and an average year as regards the meteorological circumstances;

and in which:

— the incident sound is considered, which means that no account is taken of the sound that is reflected at the façade of the dwelling under consideration (as a general rule, this implies a 3 dB correction in case of measurement).

The height of the Lden assessment point depends on the application:

— in the case of computation for the purpose of strategic noise mapping in relation to noise exposure in and near buildings, the assessment points must be 4,0 ± 0,2 m (3,8 to 4,2 m) above the ground and at the most exposed façade; for this purpose, the most exposed façade will be the external wall facing onto and nearest to the specific noise source; for other purposes other choices may be made,

— in the case of measurement for the purpose of strategic noise mapping in relation to noise exposure in and near buildings, other heights may be chosen, but they must never be less than 1,5 m above the ground, and results should be corrected in accordance with an equivalent height of 4 m,

— for other purposes such as acoustical planning and noise zoning other heights may be chosen, but they must never be less than 1,5 m above the ground, for example for: — — rural areas with one-storey houses, — the design of local measures meant to reduce the noise impact on specific dwellings, — the detailed noise mapping of a limited area, showing the noise exposure of individual dwellings.

2. Definition of the night-time noise indicator

The night-time noise indicator Lnight is the A-weighted long-term average sound level as defined in ISO 1996-2: 1987, determined over all the night periods of a year;

in which:

— the night is eight hours as defined in paragraph 1,

— a year is a relevant year as regards the emission of sound and an average year as regards the meteorological circumstances, as defined in paragraph 1,

— the incident sound is considered, as laid down in paragraph 1,

— the assessment point is the same as for Lden.

3. Supplementary noise indicators

In some cases, in addition to Lden and Lnight, and where appropriate Lday and Levening, it may be advantageous to use special noise indicators and related limit values. Some examples are given below:

— the noise source under consideration operates only for a small proportion of the time (for example, less than 20 % of the time over the total of the day periods in a year, the total of the evening periods in a year, or the total of the night periods in a year),

— the average number of noise events in one or more of the periods is very low (for example, less than one noise event an hour; a noise event could be defined as a noise that lasts less than five minutes; examples are the noise from a passing train or a passing aircraft),

— the low-frequency content of the noise is strong,

— LAmax, or SEL (sound exposure level) for night period protection in the case of noise peaks,

— extra protection at the weekend or a specific part of the year,

— extra protection of the day period,

— extra protection of the evening period,

— a combination of noises from different sources,

— quiet areas in open country,

— the noise contains strong tonal components,

— the noise has an impulsive character.

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ANNEX II

ASSESSMENT METHODS FOR THE NOISE INDICATORS

(Referred to in Article 6 of Directive 2002/49/EC)

1. INTRODUCTION

The values of Lden and Lnight shall be determined at the assessment positions by computation, according to the method set out in Chapter 2 and the data described in Chapter 3. Measurements may be performed according to Chapter 4.

2. COMMON NOISE ASSESSMENT METHODS

2.1. General provisions — Road traffic, railway and industrial noise

2.1.1. Indicators, frequency range and band definitions

Noise calculations shall be defined in ►C1 the frequency range from 63 Hz to 8 kHz octave bands ◄ . Frequency band results shall be provided at the corresponding frequency interval.

Calculations are performed in octave bands for road traffic, railway traffic and industrial noise, except for the railway noise source sound power, that 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 pressure level for the day, evening and night period, as defined in Annex I and referred to in Art. 5 of Directive 2002/49/EC, is computed by summation over all frequencies:







(2.1.1)

where

Ai denotes the A-weighting correction according to IEC 61672-1

i = frequency band index

and T is the time period corresponding to day, evening or night.

Noise parameters:







Lp Instantaneous sound pressure level [dB] (re. 2 10–5 Pa) LAeq,LT Global long-term sound level LAeq due to all sources and image sources at point R [dB] (re. 2 10–5 Pa) LW ‘In situ’ sound power level of a point source (moving or steady) [dB] (re. 10–12 W) LW,i,dir Directional ‘in situ’ sound power level for the i-th frequency band [dB] (re. 10–12 W) LW′ Average ‘in situ’ sound power level per metre of source line [dB/m] (re. 10–12 W)

Other physical parameters:







p r.m.s. of the instantaneous sound pressure [Pa] p 0 Reference sound pressure = 2 10–5 Pa [Pa] W 0 Reference sound power = 10–12 W [watt]

2.1.2. Quality framework

Accuracy of input values

All input values affecting the emission level of a source shall be determined with at least the accuracy corresponding to an uncertainty of ± 2dB(A) in the emission level of the source (leaving all other parameters unchanged).

Use of default values

In the application of the method, the input data shall reflect the actual usage. In general there shall be no reliance on default input values or assumptions. Default input values and assumptions are accepted if the collection of real data is associated with disproportionately high costs.

Quality of the software used for the calculations

Software used to perform the calculations shall prove compliance with the methods herewith described by means of certification of results against test cases.

2.2. Road traffic noise

2.2.1. Source description

Classification of vehicles

The road traffic noise source shall be determined by combining the noise emission of each individual vehicle forming the traffic flow. These vehicles are grouped into five separate categories with regard to their characteristics of noise emission:

Category 1 : Light motor vehicles

Category 2 : Medium heavy vehicles

Category 3 : Heavy vehicles

Category 4 : Powered two-wheelers

Category 5 : Open category

In the case of powered two-wheelers, two separate subclasses are defined for mopeds and more powerful motorcycles, since they operate in very different driving modes and their numbers usually vary widely.

The first four categories shall be used, and the fifth category is optional. It is foreseen for new vehicles that may be developed in the future and may be sufficiently different in their noise emission to require an additional category to be defined. This category could cover, for example, electric or hybrid vehicles or any vehicle developed in the future substantially different from those in categories 1 to 4.

The details of the different vehicle classes are given in Table [2.2.a].







Table [2.2.a] Vehicle classes Category Name Description Vehicle category in EC Whole Vehicle Type Approval (1) 1 Light motor vehicles Passenger cars, delivery vans ≤ 3,5 tons, SUVs (2), MPVs (3) including trailers and caravans M1 and N1 2 Medium heavy vehicles Medium heavy vehicles, delivery vans > 3,5 tons, buses, motorhomes, etc. with two axles and twin tyre mounting on rear axle M2, M3 and N2, N3 3 Heavy vehicles Heavy duty vehicles, touring cars, buses, with three or more axles M2 and N2 with trailer, M3 and N3 4 Powered two-wheelers 4a Two-, Three- and Four-wheel Mopeds L1, L2, L6 4b Motorcycles with and without sidecars, Tricycles and Quadricycles L3, L4, L5, L7 5 Open category To be defined according to future needs N/A (1) Directive 2007/46/EC of the European Parliament and of the Council of 5 September 2007 establishing a framework for the approval of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles (OJ L 263, 9.10.2007, p. 1). (2) Sport Utility Vehicles. (3) Multi-Purpose Vehicles.

Number and position of equivalent sound sources

In this method, each vehicle (category 1, 2, 3, 4 and 5) is represented by one single point source radiating uniformly into the 2-π half space above the ground. 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.

The traffic flow is represented by a source line. In the modelling of a road with multiple lanes, each lane should ideally be represented by a source line placed in the centre of each lane. However, it is also acceptable to model one source line in the middle of a two way road or one source line per carriageway in the outer lane of multi-lane roads.

Sound power emission

The sound power of the source is defined in the ‘semi-free field’, thus the sound power includes the effect of the reflection of the ground immediately under the modelled source where there are no disturbing objects in its immediate surroundings except for the reflection on the road surface not immediately under the modelled source.

The noise emission of a traffic flow is represented by a source line characterised by its directional sound power per metre per frequency. This corresponds to the sum of the sound emission of the individual vehicles in the traffic flow, taking into account the time spent by the vehicles in the road section considered. The implementation of the individual vehicle in the flow requires the application of a traffic flow model.

If a steady traffic flow of Qm vehicles of category m per hour is assumed, with an average speed vm (in km/h), the directional sound power per metre in frequency band i of the source line LW′, eq,line,i,m is defined by:







(2.2.1)

where LW,i,m is the directional sound power of a single vehicle. LW′,m is expressed in dB (re. 10–12 W/m). These sound power levels are calculated for ►C1 each octave band i from 63 Hz to 8 kHz ◄ .

Traffic flow data Qm shall be expressed as yearly average per hour, per time period (day-evening-night), per vehicle class and per source line. For all categories, input traffic flow data derived from traffic counting or from traffic models shall be used.

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. If local measurement data is unavailable the maximum legal speed for the vehicle category shall be used.

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

A road vehicle is modelled by a set of mathematical equations representing the two main noise sources:

1. Rolling noise due to the tyre/road interaction;

2. Propulsion noise produced by the driveline (engine, exhaust, etc.) of the vehicle.

Aerodynamic noise is incorporated in the rolling noise source.

For light, medium and heavy motor vehicles (categories 1, 2 and 3), the total sound power corresponds to the energetic sum of the rolling and the propulsion noise. Thus, the total sound power level of the source lines m = 1, 2 or 3 is defined by:







(2.2.2)

where LWR,i,m is the sound power level for rolling noise and LWP,i,m is the sound power level for propulsion noise. This is valid on all speed ranges. For speeds less than 20 km/h it shall have the same sound power level as defined by the formula for vm = 20 km/h.

For two-wheelers (category 4), only propulsion noise is considered for the source:







LW,i,m = 4 (vm = 4 ) = LWP,i,m = 4 (vm = 4 ) (2.2.3)

This is valid on all speed ranges. For speeds less than 20 km/h it shall have the same sound power level as defined by the formula for vm = 20 km/h.

2.2.2. Reference conditions

The source equations and coefficients are valid for the following reference conditions:

— a constant vehicle speed

— a flat road

— an air temperature τref = 20 °C

— a virtual reference road surface, consisting of an average of dense asphalt concrete 0/11 and stone mastic asphalt 0/11, between 2 and 7 years old and in a representative maintenance condition

— a dry road surface

— no studded tyres.

2.2.3. Rolling noise

General equation

The rolling noise sound power level in the frequency band i for a vehicle of class m = 1,2 or 3 is defined as:







(2.2.4)

The coefficients AR,i,m and BR,i,m are given in octave bands for each vehicle category and for a reference speed vref = 70 km/h. ΔLWR,i,m corresponds to the sum of the correction coefficients to be applied to the rolling noise emission for specific road or vehicle conditions deviating from the reference conditions:







ΔLWR,i,m = ΔLWR,road,i,m + ΔLstuddedtyres,i,m + ΔLWR,acc,i,m + ΔLW,temp (2.2.5)

ΔLWR,road,i,m accounts for the effect on rolling noise of a road surface with acoustic properties different from those of the virtual reference surface as defined in Chapter 2.2.2. It includes both the effect on propagation and on generation.

ΔLstudded tyres,i,m is a correction coefficient accounting for the higher rolling noise of light vehicles equipped with studded tyres.

ΔLWR,acc,i,m accounts for the effect on rolling noise of a crossing with traffic lights or a roundabout. It integrates the effect on noise of the speed variation.

ΔLW,temp is a correction term for an average temperature τ different from the reference temperature τref = 20 °C.

Correction for studded tyres

In situations where a significant number of light vehicles in the traffic flow use studded tyres during several months every year, the induced effect on rolling noise shall be taken into account. For each vehicle of category m = 1 equipped with studded tyres, a speed-dependent increase in rolling noise emission is evaluated by:







Δ stud,i ( v ) = ai + bi × lg(50/70) for v < 50 km/h (2.2.6) ai + bi × lg(v/70) for 50 ≤ v ≤ 90 km/h ai + bi × lg(90/70) for v > 90 km/h

where coefficients ai and bi are given for each octave band.

The increase in rolling noise emission shall only be attributed according to the proportion of light vehicles with studded tyres and during a limited period Ts (in months) over the year. If Qstud,ratio is the average ratio of the total volume of light vehicles per hour equipped with studded tyres during the period Ts (in months), then the yearly average proportion of vehicles equipped with studded tyres ps is expressed by:







(2.2.7)

The resulting correction to be applied to the rolling sound power emission due to the use of studded tyres for vehicles of category m = 1 in frequency band i shall be:







(2.2.8)

For vehicles of all other categories no correction shall be applied:







ΔLstuddedtyres,i,m ≠ 1 = 0 (2.2.9)

Effect of air temperature on rolling noise correction

The air temperature affects rolling noise emission; the rolling sound power level decreases when the air temperature increases. This effect is introduced in the road surface correction. Road surface corrections are usually evaluated at an air temperature of τref = 20 °C. In the case of a different yearly average air temperature °C, the road surface noise shall be corrected by:







ΔLW,temp,m (τ) = Km × (τref – τ) (2.2.10)

The correction term is positive (i.e. noise increases) for temperatures lower than 20 °C and negative (i.e. noise decreases) for higher temperatures. The coefficient K depends on the road surface and the tyre characteristics and in general exhibits some frequency dependence. A generic coefficient Km = 1 = 0,08 dB/°C for light vehicles (category 1) and Km = 2 = Km = 3 = 0,04 dB/°C for heavy vehicles (categories 2 and 3) shall be applied for all road surfaces. The correction coefficient shall be applied equally on all octave bands from 63 to 8 000 Hz.

2.2.4. Propulsion noise

General equation

The propulsion noise emission includes all contributions from engine, exhaust, gears, air intake, etc. The propulsion noise sound power level in the frequency band i for a vehicle of class m is defined as:







(2.2.11)

The coefficients AP,i,m and BP,i,m are given in octave bands for each vehicle category and for a reference speed vref = 70 km/h.

ΔLWP,i,m corresponds to the sum of the correction coefficients to be applied to the propulsion noise emission for specific driving conditions or regional conditions deviating from the reference conditions:







ΔLWP,i,m = ΔLWP,road,i,m + ΔLWP,grad,i,m + ΔLWP,acc,i,m (2.2.12)

ΔLWP,road,i,m accounts for the effect of the road surface on the propulsion noise via absorption. The calculation shall be performed according to Chapter 2.2.6.

ΔLWP,acc,i,m and ΔLWP,grad,i,m account for the effect of road gradients and of vehicle acceleration and deceleration at intersections. They shall be calculated according to Chapters 2.2.4 and 2.2.5 respectively.

Effect of road gradients

The road gradient has two effects on the noise emission of the vehicle: first, it affects the vehicle speed and thus the rolling and propulsion noise emission of the vehicle; second, it affects both the engine load and the engine speed via the choice of gear and thus the propulsion noise emission of the vehicle. Only the effect on the propulsion noise is considered in this section, where a steady speed is assumed.

The effect of the road gradient on the propulsion noise is taken into account by a correction term ΔLWP,grad,m which is a function of the slope s (in %), the vehicle speed vm (in km/h) and the vehicle class m. In the case of a bi-directional traffic flow, it is necessary to split the flow into two components and correct half for uphill and half for downhill. The correction term is attributed to all octave bands equally:

For m = 1



ΔL WP,grad,i,m = 1 ( v m ) = for s < – 6 % (2.2.13) 0 for – 6 % ≤ s ≤ 2 % for s > 2 %

For m = 2



ΔL WP,grad,i,m = 2 ( v m ) = for s < – 4 % (2.2.14) 0 for – 4 % ≤ s ≤ 0 % for s > 0 %

For m = 3



ΔL WP,grad,i,m = 3 ( v m ) = for s < – 4 % (2.2.15) 0 for – 4 % ≤ s ≤ 0 % for s > 0 %

For m = 4



ΔLWP,grad,i,m = 4 = 0 (2.2.16)

The correction ΔLWP,grad,m implicitly includes the effect of slope on speed.

2.2.5. Effect of the acceleration and deceleration of vehicles

Before and after crossings with traffic lights and roundabouts a correction shall be applied for the effect of acceleration and deceleration as described below.

The correction terms for rolling noise, ΔLWR,acc,m,k , and for propulsion noise, ΔLWP,acc,m,k , are linear functions of the distance x (in m) of the point source to the nearest intersection of the respective source line with another source line. They are attributed to all octave bands equally:







(2.2.17) (2.2.18)

The coefficients CR,m,k and CP,m,k depend on the kind of junction k (k = 1 for a crossing with traffic lights; k = 2 for a roundabout) and are given for each vehicle category. The correction includes the effect of change in speed when approaching or moving away from a crossing or a roundabout.

Note that at a distance |x| ≥ 100 m, ΔLWR,acc,m,k = ΔLWP,acc,m,k = 0.

2.2.6. Effect of the type of road surface

General principles

For road surfaces with acoustic properties different from those of the reference surface, a spectral correction term for both rolling noise and propulsion noise shall be applied.

The road surface correction term for the rolling noise emission is given by:







(2.2.19)

where

αi,m is the spectral correction in dB at reference speed vref for category m (1, 2 or 3) and spectral band i.

βm is the speed effect on the rolling noise reduction for category m (1, 2 or 3) and is identical for all frequency bands.

The road surface correction term for the propulsion noise emission is given by:







ΔLWP,road,i,m = min{αi,m ;0} (2.2.20)

Absorbing surfaces decrease the propulsion noise, while non-absorbing surfaces do not increase it.

Age effect on road surface noise properties

The noise characteristics of road surfaces vary with age and the level of maintenance, with a tendency to become louder over time. In this method the road surface parameters are derived to be representative for the acoustic performance of the road surface type averaged over its representative lifetime and assuming proper maintenance.

2.3. Railway noise

2.3.1. Source description

Classification of vehicles

For the purposes of this noise calculation method, a vehicle is defined as any single railway sub-unit of a train (typically a locomotive, a self-propelled coach, a hauled coach or a freight wagon) that can be moved independently and can be detached from the rest of the train. Some specific circumstances may occur for sub-units of a train that are a part of a non-detachable set, e.g. share one bogie between them. For the purpose of this calculation method, all these sub-units are grouped into a single vehicle.

For the purpose of this calculation method, a train consists of a series of coupled vehicles.

Table [2.3.a] defines a common language to describe the vehicle types included in the source database. It presents the relevant descriptors to be used to classify the vehicles in full. These descriptors correspond to properties of the vehicle, which affect the acoustic directional sound power per metre length of the equivalent source line modelled.

The number of vehicles for each type shall be determined on each of the track sections for each of the time periods to be used in the noise calculation. It shall be expressed as an average number of vehicles per hour, which is obtained by dividing the total number of vehicles travelling in a given time period by the duration in hours of this time period (e.g. 24 vehicles in 4 hours means 6 vehicles per hour). All vehicle types travelling on each track section shall be used.







Table [2.3.a] Classification and descriptors for railway vehicles Digit 1 2 3 4 Descriptor Vehicle type Number of axles per vehicle Brake type Wheel measure Explanation of the descriptor A letter that describes the type The actual number of axles A letter that describes the brake type A letter that describes the noise reduction measure type Possible descriptors h high speed vehicle (> 200 km/h) 1 c cast-iron block n no measure m self-propelled passenger coaches 2 k composite or sinter metal block d dampers p hauled passenger coaches 3 n non-tread braked, like disc, drum, magnetic s screens c city tram or light metro self-propelled and non-self-propelled coach 4 o other d diesel loco etc. e electric loco a any generic freight vehicle o other (i.e. maintenance vehicles etc.)

Classification of tracks and support structure

The existing tracks may differ because there are several elements contributing to and characterising their acoustic properties. The track types used in this method are listed in Table [2.3.b] below. Some of the elements have a large influence on acoustic properties, while others have only secondary effects. In general, the most relevant elements influencing the railway noise emission are: railhead roughness, rail pad stiffness, track base, rail joints and radius of curvature of the track. Alternatively, the overall track properties can be defined and, in this case, the railhead roughness and the track decay rate according to ISO 3095 are the two acoustically essential parameters, plus the radius of curvature of the track.

A track section is defined as a part of a single track, on a railway line or station or depot, on which the track's physical properties and basic components do not change.

Table [2.3.b] defines a common language to describe the track types included in the source database.







Table [2.3.b] Digit 1 2 3 4 5 6 Descriptor Track base Railhead Roughness Rail pad type Additional measures Rail joints Curvature Explanation of the descriptor Type of track base Indicator for roughness Represents an indication of the ‘acoustic’ stiffness A letter describing acoustic device Presence of joints and spacing Indicate the radius of curvature in m Codes allowed B Ballast E Well maintained and very smooth S Soft (150-250 MN/m) N None N None N Straight track S Slab track M Normally maintained M Medium (250 to 800 MN/m) D Rail damper S Single joint or switch L Low (1 000 -500 m) L Ballasted bridge N Not well maintained H Stiff (800-1 000 MN/m) B Low barrier D Two joints or switches per 100 m M Medium (Less than 500 m and more than 300 m) N Non-ballasted bridge B Not maintained and bad condition A Absorber plate on slab track M More than two joints or switches per 100 m H High (Less than 300 m) T Embedded track E Embedded rail O Other O Other

Number and position of the equivalent sound sources

The different equivalent noise line sources are placed at different heights and at the centre of the track. All heights are referred to the plane tangent to the two upper surfaces of the two rails.

The equivalent sources include different physical sources (index p). These physical sources are divided into different categories depending on the generation mechanism, and are: (1) rolling noise (including not only rail and track base vibration and wheel vibration but also, where present, superstructure noise of the freight vehicles); (2) traction noise; (3) aerodynamic noise; (4) impact noise (from crossings, switches and junctions); (5) squeal noise and (6) noise due to additional effects such as bridges and viaducts.

(1) The roughness of wheels and railheads, through three transmission paths to the radiating surfaces (rails, wheels and superstructure), constitutes the rolling noise. This is allocated to h = 0,5 m (radiating surfaces A) to represent the track contribution, including the effects of the surface of the tracks, especially slab tracks (in accordance with the propagation part), to represent the wheel contribution and to represent the contribution of the superstructure of the vehicle to noise (in freight trains).

(2) The equivalent source heights for traction noise vary between 0,5 m (source A) and 4,0 m (source B), depending on the physical position of the component concerned. Sources such as gear transmissions and electric motors will often be at an axle height of 0,5 m (source A). Louvres and cooling outlets can be at various heights; engine exhausts for diesel-powered vehicles are often at a roof height of 4,0 m (source B). Other traction sources such as fans or diesel engine blocks may be at a height of 0,5 m (source A) or 4,0 m (source B). If the exact source height is in between the model heights, the sound energy is distributed proportionately over the nearest adjacent source heights.

For this reason, two source heights are foreseen by the method at 0,5 m (source A), 4,0 m (source B), and the equivalent sound power associated with each is distributed between the two depending on the specific configuration of the sources on the unit type.

(3) Aerodynamic noise effects are associated with the source at 0,5 m (representing the shrouds and the screens, source A), and the source at 4,0 m (modelling all over roof apparatus and pantograph, source B). The choice of 4,0 m for pantograph effects is known to be a simple model, and has to be considered carefully if the objective is to choose an appropriate noise barrier height.

(4) Impact noise is associated with the source at 0,5 m (source A).

(5) Squeal noise is associated with the sources at 0,5 m (source A).

(6) Bridge noise is associated with the source at 0,5 m (source A).

2.3.2. Sound power emission

General equations

The model for railway traffic noise, analogously to road traffic noise, describes the noise sound power emission of a specific combination of vehicle type and track type which fulfils a series of requirements described in the vehicle and track classification, in terms of a set of sound power per each vehicle (LW,0).

The noise emission of a traffic flow on each track shall be represented by a set of 2 source lines characterised by its directional sound power per metre per frequency band. This corresponds to the sum of the sound emissions due to the individual vehicles passing by in the traffic flow and, in the specific case of stationary vehicles, taking into account the time spent by the vehicles in the railway section under consideration.

The directional sound power per metre per frequency band, due to all the vehicles passing by each track section on the track type (j), is defined:

— for each frequency band (i),

— for each given source height (h) (for sources at 0,5 m h = 1, at 4,0 m h = 2),

and is the energy sum of all contributions from all vehicles running on the specific j-th track section. These contributions are:

— from all vehicle types (t)

— at their different speeds (s)

— under the particular running conditions (constant speed) (c)

— for each physical source type (rolling, impact, squeal, traction, aerodynamic and additional effects sources such as for example bridge noise) (p).

To calculate the directional sound power per metre (input to the propagation part) due to the average mix of traffic on the j-th track section, the following is used:







(2.3.1)

where

Tref = reference time period for which the average traffic is considered

X = total number of existing combinations of i, t, s, c, p for each j-th track section

t = index for vehicle types on the j-th track section

s = index for train speed: there are as many indexes as the number of different average train speeds on the j-th track section

c = index for running conditions: 1 (for constant speed), 2 (idling)

p = index for physical source types: 1 (for rolling and impact noise), 2 (curve squeal), 3 (traction noise), 4 (aerodynamic noise), 5 (additional effects)

LW′,eq,line,x = x-th directional sound power per metre for a source line of one combination of t, s, c, p on each j-th track section

If a steady flow of Q vehicles per hour is assumed, with an average speed v, on average at each moment in time there will be an equivalent number of Q/v vehicles per unit length of the railway section. The noise emission of the vehicle flow in terms of directional sound power per metre LW′,eq,line (expressed in dB/m (re. 10–12 W)) is integrated by:







(for c = 1) (2.3.2)

where

— Q is the average number of vehicles per hour on the j-th track section for vehicle type t , average train speed s and running condition c

— v is their speed on the j-th track section for vehicle type t and average train speed s

— LW,0,dir is the directional sound power level of the specific noise (rolling, impact, squeal, braking, traction, aerodynamic, other effects) of a single vehicle in the directions ψ, φ defined with respect to the vehicle's direction of movement (see Figure [2.3.b]).

In the case of a stationary source, as during idling, it is assumed that the vehicle will remain for an overall time Tidle at a location within a track section with length L. Therefore, with Tref as the reference time period for the noise assessment (e.g. 12 hours, 4 hours, 8 hours), the directional sound power per unit length on that track section is defined by:







(for c = 2) (2.3.4)

In general, directional sound power is obtained from each specific source as:







LW,0,dir,i (ψ,φ) = LW,0,i + ΔLW,dir,vert,i + ΔLW,dir,hor,i (2.3.5)

where

— ΔLW,dir,vert,i is the vertical directivity correction (dimensionless) function of ψ (Figure [2.3.b])

— ΔLW,dir,hor,i is the horizontal directivity correction (dimensionless) function of φ (Figure [2.3.b]).

And where LW,0,dir,i(ψ,φ) shall, after being derived in 1/3 octave bands, be expressed in octave bands by energetically adding each pertaining 1/3 octave band together into the corresponding octave band.

For the purpose of the calculations, the source strength is then specifically expressed in terms of directional sound power per 1 m length of track LW′,tot,dir,i to account for the directivity of the sources in their vertical and horizontal direction, by means of the additional corrections.

Several LW,0,dir,i (ψ,φ) are considered for each vehicle-track-speed-running condition combination:

— for a 1/3 octave frequency band ( i )

— for each track section ( j )

— source height ( h ) (for sources at 0,5 m h = 1, at 4,0 m h = 2)

— directivity ( d ) of the source

A set of LW,0,dir,i (ψ,φ) are considered for each vehicle-track-speed-running condition combination, each track section, the heights corresponding to h = 1 and h = 2 and the directivity.

Rolling noise

The vehicle contribution and the track contribution to rolling noise are separated into four essential elements: wheel roughness, rail roughness, vehicle transfer function to the wheels and to the superstructure (vessels) and track transfer function. Wheel and rail roughness represent the cause of the excitation of the vibration at the contact point between the rail and the wheel, and the transfer functions are two empirical or modelled functions that represent the entire complex phenomena of the mechanical vibration and sound generation on the surfaces of the wheel, the rail, the sleeper and the track substructure. This separation reflects the physical evidence that roughness present on a rail may excite the vibration of the rail, but it will also excite the vibration of the wheel and vice versa. Not including one of these four parameters would prevent the decoupling of the classification of tracks and trains.

Wheel and rail roughness

Rolling noise is mainly excited by rail and wheel roughness in the wavelength range from 5-500 mm.

The roughness level Lr is defined as 10 times the logarithm to the base 10 of the square of the mean square value r2 of the roughness of the running surface of a rail or a wheel in the direction of motion (longitudinal level) measured in μm over a certain rail length or the entire wheel diameter, divided by the square of the reference value

:







dB (2.3.6)

where

r 0 = 1 μm

r = r.m.s. of the vertical displacement difference of the contact surface to the mean level

The roughness level Lr is typically obtained as a spectrum of wavelength λ and it shall be converted to a frequency spectrum f = v/λ, where f is the centre band frequency of a given 1/3 octave band in Hz, λ is the wavelength in m, ►C1 and v is the train speed in m/s ◄ . The roughness spectrum as a function of frequency shifts along the frequency axis for different speeds. In general cases, after conversion to the frequency spectrum by means of the speed, it is necessary to obtain new 1/3 octave band spectra values averaging between two corresponding 1/3 octave bands in the wavelength domain. To estimate the total effective roughness frequency spectrum corresponding to the appropriate train speed, the two corresponding 1/3 octave bands defined in the wavelength domain shall be averaged energetically and proportionally.

The rail roughness level (track side roughness) for the i-th wave-number band is defined as Lr,TR,i

By analogy, the wheel roughness level (vehicle side roughness) for the i-th wave-number band is defined as Lr,VEH,i .

The total and effective roughness level for wave-number band i (LR,tot,i ) is defined as the energy sum of the roughness levels of the rail and that of the wheel plus the ►C1 A 3(λ) ◄ contact filter to take into account the filtering effect of the contact patch between the rail and the wheel, and is in dB:







(2.3.7)

where expressed as a function of the i-th wave-number band corresponding to the wavelength λ.

The contact filter depends on the rail and wheel type and the load.

The total effective roughness for the j-th track section and each t-th vehicle type at its corresponding v speed shall be used in the method.

Vehicle, track and superstructure transfer function

Three speed-independent transfer functions, LH,TR,i LH,VEH,i and LH,VEH,SUP,i , are defined: the first for each j-th track section and the second two for each t-th vehicle type. They relate the total effective roughness level with the sound power of the track, the wheels and the superstructure respectively.

The superstructure contribution is considered only for freight wagons, therefore only for vehicle type ‘a’.

For rolling noise, therefore, the contributions from the track and from the vehicle are fully described by these transfer functions and by the total effective roughness level. When a train is idling, rolling noise shall be excluded.

For sound power per vehicle the rolling noise is calculated at axle height, and has as an input the total effective roughness level LR,TOT,i as a function of the vehicle speed v, the track, vehicle and superstructure transfer functions LH,TR,i , LH,VEH,i and LH,VEH,SUP,i , and the total number of axles Na :

for h = 1:







LW,0,TR,i = LR,TOT,i + LH,TR,i + 10 × lg(Na ) dB (2.3.8) LW,0,VEH,i = LR,TOT,i + LH,VEH,i + 10 × lg(Na ) dB (2.3.9) LW,0,VEHSUP,i = LR,TOT,i + LH,VEHSUP,i + 10 × lg(Na ) dB (2.3.10)

where Na is the number of axles per vehicle for the t-th vehicle type.

A minimum speed of 50 km/h (30 km/h only for trams and light metro) shall be used to determine the total effective roughness and therefore the sound power of the vehicles (this speed does not affect the vehicle flow calculation) to compensate for the potential error introduced by the simplification of rolling noise definition, braking noise definition and impact noise from crossings and switches definition.

Impact noise (crossings, switches and junctions)

Impact noise can be caused by crossings, switches and rail joints or points. It can vary in magnitude and can dominate rolling noise. Impact noise shall be considered for jointed tracks. For impact noise due to switches, crossings and joints in track sections with a speed of less than 50 km/h (30 km/h only for trams and light metro), since the minimum speed of 50 km/h (30 km/h only for trams and light metro) is used to include more effects according to the description of the rolling noise chapter, modelling shall be avoided. Impact noise modelling shall also be avoided under running condition c = 2 (idling).

Impact noise is included in the rolling noise term by (energy) adding a supplementary fictitious impact roughness level to the total effective roughness level on each specific j-th track section where it is present. In this case a new LR,TOT + IMPACT,i shall be used in place of LR,TOT,i and it will then become:







dB (2.3.11)

LR,IMPACT,i is a 1/3 octave band spectrum (as a function of frequency). To obtain this frequency spectrum, a spectrum is given as a function of wavelength λ and shall be converted to the required spectrum as a function of frequency using the relation λ = v/f, where f is the 1/3 octave band centre frequency in Hz ►C1 and v is the s-th vehicle speed of the t-th vehicle type in m/s ◄ .

Impact noise will depend on the severity and number of impacts per unit length or joint density, so in the case where multiple impacts are given, the impact roughness level to be used in the equation above shall be calculated as follows:







dB (2.3.12)

where LR,IMPACT–SINGLE,i is the impact roughness level as given for a single impact and nl is the joint density.

The default impact roughness level is given for a joint density nl = 0,01 m–1, which is one joint per each 100 m of track. Situations with different numbers of joints shall be approximated by adjusting the joint density nl . It should be noted that when modelling the track layout and segmentation, the rail joint density shall be taken into account, i.e. it may be necessary to take a separate source segment for a stretch of track with more joints. The LW,0 of track, wheel/bogie and superstructure contribution are incremented by means of the LR,IMPACT,i for +/– 50 m before and after the rail joint. In the case of a series of joints, the increase is extended to between – 50 m before the first joint and + 50 m after the last joint.

The applicability of these sound power spectra shall normally be verified on-site.

For jointed tracks, a default nl of 0,01 shall be used.

Squeal

Curve squeal is a special source that is only relevant for curves and is therefore localised. As it can be significant, an appropriate description is required. Curve squeal is generally dependent on curvature, friction conditions, train speed and track-wheel geometry and dynamics. The emission level to be used is determined for curves with radius below or equal to 500 m and for sharper curves and branch-outs of points with radii below 300 m. The noise emission should be specific to each type of rolling stock, as certain wheel and bogie types may be significantly less prone to squeal than others.

The applicability of these sound power spectra shall normally be verified on-site, especially for trams.

Taking a simple approach, squeal noise shall be considered by adding 8 dB for R < 300 m and 5 dB for 300 m < R < 500 m to the rolling noise sound power spectra for all frequencies. Squeal contribution shall be applied on railway track sections where the radius is within the ranges mentioned above for at least a 50 m length of track.

Traction noise

Although traction noise is generally specific to each characteristic operating condition amongst constant speed, deceleration, acceleration and idling, the only two conditions modelled are constant speed (that is valid as well when the train is decelerating or when it is accelerating) and idling. The source strength modelled only corresponds to maximum load conditions and this results in the quantities LW,0,const,i = LW,0,idling,i . Also, the LW,0,idling,i corresponds to the contribution of all physical sources of a given vehicle attributable to a specific height, as described in 2.3.1.

The LW,0,idling,i is expressed as a static noise source in the idling position, for the duration of the idling condition, and to be used modelled as a fixed point source as described in the following chapter for industrial noise. It shall be considered only if trains are idling for more than 0,5 hours.

These quantities can either be obtained from measurements of all sources at each operating condition, or the partial sources can be characterised individually, determining their parameter dependency and relative strength. This may be done by means of measurements on a stationary vehicle, by varying shaft speeds of the traction equipment, following ISO 3095:2005. As far as relevant, several traction noise sources have to be characterised which might not be all directly depending on the train speed:

— noise from the power train, such as diesel engines (including inlet, exhaust and engine block), gear transmission, electrical generators, mainly dependent on engine round per minute speed (rpm), and electrical sources such as converters, which may be mostly load-dependent,

— noise from fans and cooling systems, depending on fan rpm; in some cases fans can be directly coupled to the driveline,

— intermittent sources such as compressors, valves and others with a characteristic duration of operation and corresponding duty cycle correction for the noise emission.

As each of these sources can behave differently at each operating condition, the traction noise shall be specified accordingly. The source strength is obtained from measurements under controlled conditions. In general, locomotives will tend to show more variation in loading as the number of vehicles hauled and thereby the power output can vary significantly, whereas fixed train formations such as electric motored units (EMUs), diesel motored units (DMUs) and high-speed trains have a better defined load.

There is no a priori attribution of the source sound power to the source heights, and this choice shall depend on the specific noise and vehicle assessed. It shall be modelled to be at source A (h = 1) and at source B (h = 2).

Aerodynamic noise

Aerodynamic noise is only relevant at high speeds above 200 km/h and therefore it should first be verified whether it is actually necessary for application purposes. If the rolling noise roughness and transfer functions are known, it can be extrapolated to higher speeds and a comparison can be made with existing high-speed data to check whether higher levels are produced by aerodynamic noise. If train speeds on a network are above 200 km/h but limited to 250 km/h, in some cases it may not be necessary to include aerodynamic noise, depending on the vehicle design.

The aerodynamic noise contribution is given as a function of speed:







dB For h = 1 (2.3.13) dB For h = 2 (2.3.14)

where

v 0 is a speed at which aerodynamic noise is dominant and is fixed at 300 km/h

LW,0,1,i is a reference sound power determined from two or more measurement points, for sources at known source heights, for example the first bogie

LW,0,2,i is a reference sound power determined from two or more measurement points, for sources at known source heights, for example the pantograph recess heights

α1,i is a coefficient determined from two or more measurement points, for sources at known source heights, for example the first bogie

α2,i is a coefficient determined from two or more measurement points, for sources at known source heights, for example the pantograph recess heights.

Source directivity

The horizontal directivity ΔLW,dir,hor,i in dB is given in the horizontal plane and by default can be assumed to be a dipole for rolling, impact (rail joints etc.), squeal, braking, fans and aerodynamic effects, given for each i-th frequency band by:







ΔLW,dir,hor,i = 10 × lg(0,01 + 0,99 · sin2 φ) (2.3.15)

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 – π/2 < ψ < π/2 by:







(2.3.16)

For source B (h = 2) for the aerodynamic effect:







ΔLW,dir,ver,i = 10 × lg(cos2 ψ) for ψ < 0 (2.3.17)

ΔLW,dir,ver,i = 0 elsewhere

Directivity ΔLdir,ver,i is not considered for source B (h = 2) for other effects, as omni-directionality is assumed for these sources in this position.

2.3.3. Additional effects

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. Because it is not simple to model the bridge emission as an additional source, given the complex shapes of bridges, an increase in the rolling noise is used to account for the bridge noise. The increase shall be modelled exclusively by adding a fixed increase in the noise sound power per each third octave band. The sound power of only the rolling noise is modified when considering the correction and the new LW,0,rolling–and–bridge,i shall be used instead of LW,0,rolling-only,i :







LW,0,rolling–and–bridge,i = LW,0,rolling–only,i + Cbridge dB (2.3.18)

where Cbridge is a constant that depends on the bridge type, and LW,0,rolling–only,i is the rolling noise sound power on the given bridge that depends only on the vehicle and track properties.

Correction for other railway-related noise sources

Various sources like depots, loading/unloading areas, stations, bells, station loudspeakers, etc. can be present and are associated with the railway noise. These sources are to be treated as industrial noise sources (fixed noise sources) and shall be modelled, if relevant, according to the following chapter for industrial noise.

2.4. Industrial noise

2.4.1. Source description

Classification of source types (point, line, area)

The industrial sources are of very variable dimensions. They can be large industrial plants as well as small concentrated sources like small tools or operating machines used in factories. Therefore, it is necessary to use an appropriate modelling technique for the specific source under assessment. Depending on the dimensions and the way several single sources extend over an area, with each belonging to the same industrial site, these may be modelled as point sources, source lines or area sources. In practice, the calculations of the noise effect are always based on point sources, but several point sources can be used to represent a real complex source, which mainly extends over a line or an area.

Number and position of equivalent sound sources

The real sound sources are modelled by means of equivalent sound sources represented by one or more point sources so that the total sound power of the real source corresponds to the sum of the single sound powers attributed to the different point sources.

The general rules to be applied in defining the number of point sources to be used are:

— line or surface sources where the largest dimension is less than 1/2 of the distance between the source and the receiver can be modelled as single point sources,

— sources where the largest dimension is more than 1/2 of the distance between the source and the receiver should be modelled as a series of incoherent point sources in a line or as a series of incoherent point sources over an area, such that for each of these sources the condition of 1/2 is fulfilled. The distribution over an area can include vertical distribution of point sources,

— for sources where the largest dimensions in height are over 2 m or near the ground, special care should be administered to the height of the source. Doubling the number of sources, redistributing them only in the z-component, may not lead to a significantly better result for this source,

— in the case of any source, doubling the number of sources over the source area (in all dimensions) may not lead to a significantly better result.

The position of the equivalent sound sources cannot be fixed, given the large number of configurations that an industrial site can have. Best practices will normally apply.

Sound power emission

The following information constitutes the complete set of input data for sound propagation calculations with the methods to be used for noise mapping:

— Emitted sound power level spectrum in octave bands

— Working hours (day, evening, night, on a yearly averaged basis)

— Location (coordinates x, y) and elevation (z) of the noise source

— Type of source (point, line, area)

— Dimensions and orientation

— Operating conditions of the source

— Directivity of the source.

The point, line and area source sound power are required to be defined as:

— For a point source, sound power LW and directivity as a function of the three orthogonal coordinates (x, y, z);

— Two types of source lines can be defined:

— source lines representing conveyor belts, pipe lines, etc., sound power per metre length LW′ and directivity as a function of the two orthogonal coordinates to the axis of the source line,

— source lines representing moving vehicles, each associated with sound power LW and directivity as a function of the two orthogonal coordinates to the axis of the source line and sound power per metre LW′ derived by means of the speed and number of vehicles travelling along this line during day, evening and night; The correction for the working hours, to be added to the source sound power to define the corrected sound power that is to be used for calculations over each time period, CW in dB is calculated as follows: —



(2.4.1) — Where: — V Speed of the vehicle [km/h]; n Number of vehicles passages per period [-]; l Total length of the source [m].

— For an area source, sound power per square metre LW/m2 , and no directivity (may be horizontal or vertical).

The working hours are an essential input for the calculation of noise levels. The working hours shall be given for the day, evening and night period and, if the propagation is using different meteorological classes defined during each of the day, night and evening periods, then a finer distribution of the working hours shall be given in sub-periods matching the distribution of meteorological classes. This information shall be based on a yearly average.

The correction for the working hours, to be added to the source sound power to define the corrected sound power that shall be used for calculations over each time period, CW in dB is calculated as follows:







(2.4.2)

where

T is the active source time per period based on a yearly averaged situation, in hours;

Tref is the reference period of time in hours (e.g. day is 12 hours, evening is 4 hours, night is 8 hours).

For the more dominant sources, the yearly average working hours correction shall be estimated at least within 0,5 dB tolerance in order to achieve an acceptable accuracy (this is equivalent to an uncertainty of less than 10 % in the definition of the active period of the source).

Source directivity

The source directivity is strongly related to the position of the equivalent sound source next to nearby surfaces. Because the propagation method considers the reflection of the nearby surface as well its sound absorption, it is necessary to consider carefully the location of the nearby surfaces. In general, these two cases will always be distinguished:

— a source sound power and directivity is determined and given relative to a certain real source when this is in free field (excluding the terrain effect). This is in agreement with the definitions concerning the propagation, if it is assumed that there is no nearby surface less than 0,01 m from the source and surfaces at 0,01 m or more are included in the calculation of the propagation,

— a source sound power and directivity is determined and given relative to a certain real source when this is placed in a specific location and therefore the source sound power and directivity is in fact an ‘equivalent’ one, since it includes the modelling of the effect of the nearby surfaces. This is defined in ‘semi-free field’ according to the definitions concerning the propagation. In this case, the nearby surfaces modelled shall be excluded from the calculation of propagation.

The directivity shall be expressed in the calculation as a factor ΔLW,dir,xyz (x, y, z) to be added to the sound power to obtain the right directional sound power of a reference sound source seen by the sound propagation in the direction given. The factor can be given as a function of the direction vector defined by (x,y,z) with

. This directivity can also be expressed by means of other coordinate systems such as angular coordinate systems.

2.5. Calculation of noise propagation for road, railway, industrial sources.

2.5.1. Scope and applicability of the method

This document specifies a method for calculating the attenuation of noise during its outdoor propagation. Knowing the characteristics of the source, this method predicts the equivalent continuous sound pressure level at a receiver point corresponding to two particular types of atmospheric conditions:

— downward-refraction propagation conditions (positive vertical gradient of effective sound celerity) from the source to the receiver,

— homogeneous atmospheric conditions (null vertical gradient of effective sound celerity) over the entire area of propagation.

The method of calculation described in this document applies to industrial infrastructures and land transport infrastructures. It therefore applies in particular to road and railway infrastructures. Aircraft transport is included in the scope of the method only for the noise produced during ground operations and excludes take-off and landing.

Industrial infrastructures that emit impulsive or strong tonal noises as described in ISO 1996-2:2007 do not fall within the scope of this method.

The method of calculation does not provide results in upward-refraction propagation conditions (negative vertical gradient of effective sound speed) but these conditions are approximated by homogeneous conditions when computing Lden.

To calculate the attenuation due to atmospheric absorption in the case of transport infrastructure, the temperature and humidity conditions are calculated according to ISO 9613-1:1996.

The method provides results per octave band, from 63 Hz to 8 000 Hz. The calculations are made for each of the centre frequencies.

Partial covers and obstacles sloping, when modelled, more than 15° in relation to the vertical are out of the scope of this calculation method.

A single screen is calculated as a single diffraction calculation, two or more screens in a single path are treated as a subsequent set of single diffractions by applying the procedure described further.

2.5.2. Definitions used

All distances, heights, dimensions and altitudes used in this document are expressed in metres (m).

The notation MN stands for the distance in 3 dimensions (3D) between the points M and N, measured according to a straight line joining these points.

The notation ^MN stands for the curved path length between the points M and N, in favourable conditions.

It is customary for real heights to be measured vertically in a direction perpendicular to the horizontal plane. Heights of points above the local ground are denoted h, absolute heights of points and absolute height of the ground are to be noted by the letter H.

To take into account the actual relief of the land along a propagation path, the notion of ‘equivalent height’ is introduced, to be noted by the letter z. This substitutes real heights in the ground effect equations.

The sound levels, noted by the capital letter L, are expressed in decibels (dB) per frequency band when index A is omitted. The sound levels in decibels dB(A) are given the index A.

The sum of the sound levels due to mutually incoherent sources is noted by the sign in accordance with the following definition:







(2.5.1)

2.5.3. Geometrical considerations

Source segmentation

Real sources are described by a set of point sources or, in the case of railway traffic or road traffic, by incoherent source lines. The propagation method assumes that line or area sources have previously been split up to be represented by a series of equivalent point sources. This may have occurred as pre-processing of the source data, or may occur within the pathfinder component of the calculation software. The means by which this has occurred is outside the scope of the current methodology.

Propagation paths

The method operates on a geometrical model consisting of a set of connected ground and obstacles surfaces. A vertical propagation path is deployed on one or more vertical planes with respect to the horizontal plane. For trajectories including reflections onto vertical surfaces not orthogonal to the incident plane, another vertical plane is subsequently considered including the reflected part of the propagation path. In these cases, where more vertical planes are used to describe the entire trajectory from the source to the receiver, the vertical planes are then flattened, like an unfolding Chinese screen.

Significant heights above the ground

The equivalent heights are obtained from the mean ground plane between the source and the receiver. This replaces the actual ground with a fictitious plane representing the mean profile of the land.

1 : Actual relief

2 : Mean plane

The equivalent height of a point is its orthogonal height in relation to the mean ground plane. The equivalent source height zs and the equivalent receiver height zr can therefore be defined. The distance between the source and receiver in projection over the mean ground plane is noted by dp .

If the equivalent height of a point becomes negative, i.e. if the point is located below the mean ground plane, a null height is retained, and the equivalent point is then identical with its possible image.

Calculation of the mean plane

In the plane of the path, the topography (including terrain, mounds, embankments and other man-made obstacles, buildings, …) may be described by an ordered set of discrete points (xk, Hk ); k є {1,…,n}. This set of points defines a polyline, or equivalently, a sequence of straight segments Hk = akx + bk, x є [xk, xk + 1 ]; k є {1,…n}, where:







ak = (Hk + 1 – Hk )/(xk + 1 – xk ) (2.5.2) bk = (Hk · xk + 1 – Hk + 1 · xk )/(xk + 1 – xk )

The mean plane is represented by the straight line Z = ax + b; x є [x 1, xn ], which is adjusted to the polyline by means of a least-square approximation. The equation of the mean line can be worked out analytically.

Using:







(2.5.3)

The coefficients of the straight line are given by:







(2.5.4)

Where segments with xk + 1 = xk shall be ignored when evaluating eq. 2.5.3.

Reflections by building façades and other vertical obstacles

Contributions from reflections are taken into account by the introduction of image sources as described further.

2.5.4. Sound propagation model

For a receiver R the calculations are made according to the following steps:

(1) on each propagation path:

— calculation of the attenuation in favourable conditions,

— calculation of the attenuation in homogeneous conditions,

— calculation of the long-term sound level for each path;

(2) accumulation of the long-term sound levels for all paths affecting a specific receiver, therefore allowing the total sound level to be calculated at the receiver point.

It should be noted that only the attenuations due to the ground effect (Aground ) and diffraction (Adif ) are affected by meteorological conditions.

2.5.5. Calculation process

For a point source S of directional sound power Lw,0,dir and for a given frequency band, the equivalent continuous sound pressure level at a receiver point R in given atmospheric conditions is obtained according to the equations following below.

Sound level in favourable conditions (LF) for a path (S,R)







LF = LW,0,dir – AF (2.5.5)

The term AF represents the total attenuation along the propagation path in favourable conditions, and is broken down as follows:







LF = Adiv + Aatm + Aboundary,F (2.5.6)

where

Adiv is the attenuation due to geometrical divergence;

Aatm is the attenuation due to atmospheric absorption;

Aboundary,F is the attenuation due to the boundary of the propagation medium in favourable conditions. It may contain the following terms: Aground,F which is the attenuation due to the ground in favourable conditions; Adif,F which is the attenuation due to diffraction in favourable conditions.

For a given path and frequency band, the following two scenarios are possible:

— either Aground,F is calculated with no diffraction (Adif,F = 0 dB) and Aboundary,F = Aground,F ;

— or Adif,F is calculated. The ground effect is taken into account in the Adif,F equation itself (Aground,F = 0 dB). This therefore gives Aboundary,F = Adif,F .

Sound level in homogeneous conditions (LH) for a path (S,R)

The procedure is strictly identical to the case of favourable conditions presented in the previous section.







LH = LW,0,dir – AH (2.5.7)

The term AH represents the total attenuation along the propagation path in homogeneous conditions and is broken down as follows:







AH = Adiv + Aatm + Aboundary,H (2.5.8)

where

Adiv is the attenuation due to geometrical divergence;

Αatm is the attenuation due to atmospheric absorption;

Aboundary,H is the attenuation due to the boundary of the propagation medium in homogeneous conditions. It may contain the following terms: Αground,H which is the attenuation due to the ground in homogeneous conditions; Adif,H which is the attenuation due to diffraction in homogeneous conditions.

For a given path and frequency band, the following two scenarios are possible:

— either Αground,H (Adif,H = 0 dB) is calculated with no diffraction and Aboundary,H = Αground,H ;

— or Adif,H (Αground,H = 0 dB) is calculated. The ground effect is taken into account in the Adif,H equation itself. This therefore gives Aboundary,H = Adif,H

Statistical approach inside urban areas for a path (S,R)

Inside urban areas, a statistical approach to the calculation of the sound propagation behind the first line of buildings is also allowed, provided that such a method is duly documented, including relevant information on the quality of the method. This method may replace the calculation of the Aboundary,H and Aboundary,F by an approximation of the total attenuation for the direct path and all reflections. The calculation will be based on the average building density and the average height of all buildings in the area.

Long-term sound level for a path (S,R)

The ‘long-term’ sound level along a path starting from a given point source is obtained from the logarithmic sum of the weighted sound energy in homogeneous conditions and the sound energy in favourable conditions.

These sound levels are weighted by the mean occurrence p of favourable conditions in the direction of the path (S,R):







(2.5.9)

NB: The occurrence values for p are expressed in percentages. So for example, if the occurrence value is 82 %, equation (2.5.9) would have p = 0,82.

Long-term sound level at point R for all paths

The total long-term sound level at the receiver for a frequency band is obtained by energy summing contributions from all N paths, all types included:







(2.5.10)

where

n is the index of the paths between S and R.

Taking reflections into account by means of image sources is described further. The percentage of occurrences of favourable conditions in the case of a path reflected on a vertical obstacle is taken to be identical to the occurrence of the direct path.

If S′ is the image source of S, then the occurrence p′ of the path (S′,R) is taken to be equal to the occurrence p of the path (Si,R).

Long-term sound level at point R in decibels A (dBA)

The total sound level in decibels A (dBA) is obtained by summing levels in each frequency band:







(2.5.11)

where i is the index of the frequency band. AWC is the A-weighting correction according to the international standard IEC 61672-1:2003.

This level LAeq,LT constitutes the final result, i.e. the long-term A-weighted sound pressure level at the receiver point on a specific reference time interval (e.g. day or evening, or night or a shorter time during day, evening or night).

2.5.6. Calculation of noise propagation for road, railway, industrial sources.

Geometrical divergence

The attenuation due to geometrical divergence, Adiv, corresponds to a reduction in the sound level due to the propagation distance. For a point sound source in free field, the attenuation in dB is given by:







Adiv = 20 × lg(d) + 11 (2.5.12)

where d is the direct 3D slant distance between the source and the receiver.

Atmospheric absorption

The attenuation due to atmospheric absorption Aatm during propagation over a distance d is given in dB by the equation:







Aatm = αatm · d/1 000 (2.5.13)

where

d is the direct 3D slant distance between the source and the receiver in m;

αatm is the atmospheric attenuation coefficient in dB/km at the nominal centre frequency for each frequency band, in accordance with ISO 9613-1.

The values of the αatm coefficient are given for a temperature of 15 °C, a relative humidity of 70 % and an atmospheric pressure of 101 325 Pa. They are calculated with the exact centre frequencies of the frequency band. These values comply with ISO 9613-1. Meteorological average over the long term shall be used if meteorological data is available.

Ground effect

The attenuation due to the ground effect is mainly the result of the interference between the reflected sound and the sound that is propagated directly from the source to the receiver. It is physically linked to the acoustic absorption of the ground above which the sound wave is propagated. However, it is also significantly dependent on atmospheric conditions during propagation, as ray bending modifies the height of the path above the ground and makes the ground effects and land located near the source more or less significant.

In case the propagation between the source and the receiver is affected by any obstacle in the propagation plane, the ground effect is calculated separately on the source and receiver side. In this case, zs and zr refer to the equivalent source and/or receiver position as indicated further where the calculation of the diffraction Adif is presented.

Acoustic characterisation of ground

The acoustic absorption properties of the ground are mainly linked to its porosity. Compact ground is generally reflective and porous ground is absorbent.

For operational calculation requirements, the acoustic absorption of a ground is represented by a dimensionless coefficient G, between 0 and 1. G is independent of the frequency. Table 2.5.a gives the G values for the ground outdoors. In general, the average of the coefficient G over a path takes values between 0 and 1.







Table 2.5.a G values for different types of ground Description Type (kPa · s/m2) G value Very soft (snow or moss-like) A 12,5 1 Soft forest floor (short, dense heather-like or thick moss) B 31,5 1 Uncompacted, loose ground (turf, grass, loose soil) C 80 1 Normal uncompacted ground (forest floors, pasture field) D 200 1 Compacted field and gravel (compacted lawns, park area) E 500 0,7 Compacted dense ground (gravel road, car park) F 2 000 0,3 Hard surfaces (most normal asphalt, concrete) G 20 000 0 Very hard and dense surfaces (dense asphalt, concrete, water) H 200 000 0

Gpath is defined as the fraction of absorbent ground present over the entire path covered.

When the source and receiver are close-by so that dp ≤ 30(zs + zr ), the distinction between the type of ground located near the source and the type of ground located near the receiver is negligible. To take this comment into account, the ground factor Gpath is therefore ultimately corrected as follows:







G′ path = if dp ≤ 30(zs + zr ) (2.5.14) Gpath otherwise

where Gs is the ground factor of the source area. Gs = 0 for road platforms ( 3 ), slab tracks. Gs = 1 for rail tracks on ballast. There is no general answer in the case of industrial sources and plants.

G may be linked to the flow resistivity.

The following two subsections on calculations in homogeneous and favourable conditions introduce the generic

w and

m notations for the absorption of the ground. Table 2.5.b gives the correspondence between these notations and the Gpath and G′path variables.







Table 2.5.b Correspondence between w and m and (Gpath , G′path ) Homogeneous conditions Favourable conditions Aground Δground(S,O) Δground(O,R) Ag round Δground(S,O) Δground(O,R) w G′path Gpath m G′path Gpath G′path Gpath

Calculations in homogeneous conditions

The attenuation due to the ground effect in homogeneous conditions is calculated according to the following equations:

if Gpath ≠ 0







(2.5.15)

where

fm is the nominal centre frequency of the frequency band considered, in Hz, c is the speed of the sound in the air, taken as equal to 340 m/s, and Cf is defined by:







(2.5.16)

where the values of w are given by the equation below:







(2.5.17)

w may be equal to either Gpath or G′path depending on whether the ground effect is calculated with or without diffraction, and according to the nature of the ground under the source (real source or diffracted). This is specified in the following subsections and summarised in Table 2.5.b.







(2.5.18)

is the lower bound of Aground,H .

For a path (Si,R) in homogeneous conditions without diffraction:

w = G′path

m = G′path

With diffraction, refer to the section on diffraction for the definitions of

w and

m .

if Gpath = 0: Aground,H = – 3 dB

The term – 3(1 –

m ) takes into account the fact that when the source and the receiver are far apart, the first reflection source side is no longer on the platform but on natural land.

Calculation in favourable conditions

The ground effect in favourable conditions is calculated with the equation of Aground,H , provided that the following modifications are made:

If Gpath ≠ 0 (a) In the equation of Aground,H , the heights zs and zr are replaced by zs + δ zs + δ zT and zr + δ zr + δ zT respectively where



(2.5.19) ao =2 × 10–4 m–1 is the reverse of the radius of curvature (b) The lower bound of Aground,F depends on the geometry of the path:



►C1 ◄ (2.5.20)

If Gpath = 0 Aground,F = Aground,F,min

The height corrections δ zs and δ zr convey the effect of the sound ray bending. δ zT accounts for the effect of the turbulence.

m may also be equal to either Gpath or G′path depending on whether the ground effect is calculated with or without diffraction, and according to the nature of the ground under the source (real source or diffracted). This is specified in the following subsections.

For a path (Si,R) in favourable conditions without diffraction:

w = Gpath in equation (2.5.17);

m = G′path .

With diffraction, refer to the next section for the definitions of

w and

m .

Diffraction

As a general rule, the diffraction shall be studied at the top of each obstacle located on the propagation path. If the path passes ‘high enough’ over the diffraction edge, Adif = 0 can be set and a direct view calculated, in particular by evaluating Aground .

In practice, for each frequency band centre frequency, the path difference δ is compared with the quantity – λ/20. If an obstacle does not produce diffraction, this for instance being determined according to Rayleigh's criterion, there is no need to calculate Adif for the frequency band considered. In other words, Adif = 0 in this case. Otherwise, Adif is calculated as described in the remainder of this part. This rule applies in both homogeneous and favourable conditions, for both single and multiple diffraction.

When, for a given frequency band, a calculation is made according to the procedure described in this section, Aground is set as equal to 0 dB when calculating the total attenuation. The ground effect is taken into account directly in the general diffraction calculation equation.

The equations proposed here are used to process the diffraction on thin screens, thick screens, buildings, earth berms (natural or artificial), and by the edges of embankments, cuttings and viaducts.

When several diffracting obstacles are encountered on a propagation path, they are treated as a multiple diffraction by applying the procedure described in the following section on calculation of the path difference.

The procedures presented here are used to calculate the attenuations in both homogeneous conditions and favourable conditions. Ray bending is taken into account in the calculation of the path difference and to calculate the ground effects before and after diffraction.

General principles

Figure 2.5.c illustrates the general method of calculation of the attenuation due to diffraction. This method is based on breaking down the propagation path into two parts: the ‘source side’ path, located between the source and the diffraction point, and the ‘receiver side’ path, located between the diffraction point and the receiver.

The following are calculated:

— a ground effect, source side, Δ ground(S,O)

— a ground effect, receiver side, Δ ground(O,R)

— and three diffractions: — — between the source S and the receiver R: Δ dif(S,R) — between the image source S′ and R: Δ dif(S′,R) — between S and the image receiver R′: Δ dif(S,R′) .

1 : Source side

2 : Receiver side

where

S is the source;

R is the receiver;

S′ is the image source in relation to the mean ground plane source side;

R′ is the image receiver in relation to the mean ground plane receiver side;

O is the diffraction point;

z s is the equivalent height of the source S in relation to the mean plane source side;

z o,s is the equivalent height of the diffraction point O in relation to the mean ground plane source side;

z r is the equivalent height of the receiver R in relation to the mean plane receiver side;

z o,r is the equivalent height of the diffraction point O in relation to the mean ground plane receiver side.

The irregularity of the ground between the source and the diffraction point, and between the diffraction point and the receiver, is taken into account by means of equivalent heights calculated in relation to the mean ground plane, source side first and receiver side second (two mean ground planes), according to the method described in the subsection on significant heights above the ground.

Pure diffraction

For pure diffraction, with no ground effects, the attenuation is given by:







Δ dif = if (2.5.21) 0 otherwise

where







Ch = 1 (2.5.22)

λ is the wavelength at the nominal centre frequency of the frequency band considered;

δ is the path difference between the diffracted path and the direct path (see next subsection on calculation of the path difference);

C″ is a coefficient used to take into account multiple diffractions:

C″ = 1 for a single diffraction.

For a multiple diffraction, if e is the total distance along the path, O1 to O2 + O2 to O3 + O3 to O4 from the ‘rubber band method’, (see Figures 2.5.d and 2.5.f) and if e exceeds 0,3 m (otherwise C″ = 1), this coefficient is defined by:







(2.5.23)

The values of Δdif shall be bound:

— if Δ dif < 0: Δ dif = 0 dB

— if Δ dif > 25: Δ dif = 25 dB for a diffraction on a horizontal edge and only on the term Δdif which figures in the calculation of Adif . This upper bound shall not be applied in the Δdif terms that intervene in the calculation of Δ ground , or for a diffraction on a vertical edge (lateral diffraction) in the case of industrial noise mapping.

Calculation of the path difference

The path difference δ is calculated in a vertical plane containing the source and the receiver. This is an approximation in relation to the Fermat principle. The approximation remains applicable here (source lines). The path difference δ is calculated as in the following Figures, based on the situations encountered.

Homogeneous conditions

Note: For each configuration, the expression of δ is given.

Favourable conditions

In favourable conditions, it is considered that the three curved sound rays ►C1 , and ◄ have an identical radius of curvature Γ defined by:







Γ = max(1 000,8 d) (2.5.24)

The length of a sound ray curve MN is noted ^MN in favourable conditions. This length is equal to:







(2.5.25)

In principle, three scenarios should be considered in the calculation of the path difference in favourable conditions δF (see Figure 2.5.e). In practice, two equations are sufficient:

— if the straight sound ray SR is masked by the obstacle (1st and 2nd case in Figure 2.5.e): —



(2.5.26)

— if the straight sound ray SR is not masked by the obstacle (3rd case in Figure 2.5.e): —



(2.5.27)

where A is the intersection of the straight sound ray SR and the extension of the diffracting obstacle.

For the multiple diffractions in favourable conditions:

— determine the convex hull defined by the various potential diffraction edges;

— eliminate the diffraction edges which are not on the boundary of the convex hull;

— calculate δF based on the lengths of the curved sound ray, by breaking down the diffracted path into as many curved segments as necessary (see Figure 2.5.f) —



(2.5.28)

In the scenario presented in Figure 2.5.f, the pat