Regulation No. 51-02

Name:Regulation No. 51-02
Description:Noise.
Official Title:Uniform Provisions Concerning the Approval of: Motor Vehicles Having a Least Four Wheels with Regard to their Noise Emissions.
Country:ECE - United Nations
Date of Issue:1983-01-11
Amendment Level:02 Series, Supplement 10
Number of Pages:64
Vehicle Types:Agricultural Tractor, Bus, Car, Heavy Truck, Light Truck
Subject Categories:Prior Versions
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Keywords:

vehicle, test, speed, engine, vehicles, gear, noise, approval, type, measurement, regulation, sound, acceleration, maximum, paragraph, annex, measurements, level, mass, system, line, series, microphone, surface, ratio, amendments, manufacturer, exhaust, power, reference, results, requirements, case, made, point, date, figure, measured, conditions, ece, position, force, measuring, entry, tested, target, supplement, category, rated, number

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E/ECE/324
) Rev.1/Add.50/Rev.2/Amend.3
E/ECE/TRANS/505 )
February 3, 2015
STATUS OF UNITED NATIONS REGULATION
ECE 51-02
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF:
MOTOR VEHICLES HAVING AT LEAST FOUR WHEELS
WITH REGARD TO THEIR NOISE EMISSIONS
Incorporating:
02 series of amendments
Date of Entry into Force: 18.04.95
Supplement 1 to the 02 series of amendments
Date of Entry into Force: 05.05.96
Corr. 1 to the 02 series of amendments
Dated: 15.11.96
Corr. 2 to the 02 series of amendments
Dated: 11.03.98
Corr. 3 to the 02 series of amendments
Dated: 28.04.11
Supplement 2 to the 02 series of amendments
Date of Entry into Force: 07.02.99
Supplement 3 to the 02 series of amendments
Date of Entry into Force: 17.11.99
Corr. 1 to Supplement 3 to the 02 series of amendments
Dated: 07.03.01
Supplement 4 to the 02 series of amendments
Date of Entry into Force: 02.02.07
Supplement 5 to the 02 series of amendments
Date of Entry into Force: 18.06.07
Supplement 6 to the 02 series of amendments
Date of Entry into Force: 03.02.08
Supplement 7 to the 02 series of amendments
Date of Entry into Force: 30.01.11
Corr. 1 to Revision 2 of the Regulation
Dated: 14.03.12
Supplement 8 to the 02 series of amendments
Date of Entry into Force: 13.04.12
Supplement 9 to the 02 series of amendments
Date of Entry into Force: 03.11.13
Supplement 10 to the 02 series of amendments
Date of Entry into Force: 22.01.15

REGULATION NO. 51
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF MOTOR VEHICLES HAVING AT
LEAST FOUR WHEELS WITH REGARD TO THEIR NOISE EMISSIONS
1. Scope
2. Definitions
3. Application for approval
4. Markings
5. Approval
6. Specifications
CONTENTS
7. Modifications and extension of approval of a vehicle type
8. Conformity of production
9. Penalties for non-conformity of production
10. Production definitively discontinued
11. Transitional provisions
12. Names and addresses of technical services responsible for conducting approval tests and of Type
Approval Authorities

REGULATION NO. 51
UNIFORM PROVISIONS CONCERNING THE APPROVAL OF MOTOR VEHICLES HAVING AT
LEAST FOUR WHEELS WITH REGARD TO THEIR NOISE EMISSIONS
1. SCOPE
This Regulation applies to vehicles of Category M and N
with regard to noise.
2. DEFINITIONS
For the purposes of this Regulation,
2.1. "Approval of a vehicle" means the approval of a vehicle type with regard to noise;
2.2. "Vehicle type" means a category of motor vehicles which do not differ in such essential
respects as:
2.2.1. the shape or materials of the bodywork (particularly the engine compartment and its
soundproofing);
2.2.2. the length and width of the vehicle;
2.2.3. the type of engine (positive or compression ignition, two- or four-stroke, reciprocating or rotary
piston), number and capacity of cylinders, number and type of carburettors or injection system,
arrangement of valves, rated maximum power and corresponding engine speed(s), or the type
of electric motor;
2.2.4. the transmission system, the number of gears and ratios;
2.2.5. the noise reduction system as defined in the following Paragraphs 2.3 and 2.4.
2.2.6. Notwithstanding the provisions of Paragraphs 2.2.2. and 2.2.4., vehicles other than those in
Categories M and N having the same type of engine and/or different overall gear ratios,
may be regarded as vehicles of the same type.
However, if the above differences provide for a different test method, these differences are to
be considered as a change of type.
2.3. "Noise reduction system" means a complete set of components necessary for limiting the
noise made by a motor vehicle and its exhaust;
2.4. "Noise reduction systems of different types" means noise reduction systems which differ in
such essential respects as:
2.4.1. that their components as specified in Paragraph 4.1., bear different trade names or marks;
2.4.2. that the characteristics of the materials constituting a component are different or that the
components differ in shape or size, a change in the plating procedure (galvanisation, aluminium
coating, etc.) is not deemed to produce a difference of type;

2.12. "Engine" means the power source without detachable accessories.
2.13. "Target acceleration" means an acceleration at a partial throttle condition in urban traffic and
is derived from statistical investigations.
2.14. "Reference acceleration" means the required acceleration during the acceleration test on the
test track.
2.15. "Gear ratio weighting factor k" means a dimensionless numerical quantity used to combine
the test results of two gear ratios for the acceleration test and the constant speed test.
2.16. "Partial power factor k " means a numerical quantity with no dimension used for the weighted
combination of the test results of the acceleration test and the constant speed test for vehicles.
2.17. "Pre-acceleration" means application of acceleration control device prior to AA' for the
purpose of achieving stable acceleration between AA' and BB'.
2.18. "Locked gear ratios" means the control of transmission such that the transmission gear
cannot change during a test.
2.19. "Design family of silencing system or silencing system components"
Silencing systems or components thereof belong to the same design family if all of the following
characteristics are the same:
(a)
(b)
(c)
(d)
The exhaust gases in contact with the absorbing fibrous material have net gas flow
through this material: (yes or no);
The type of the fibres (e.g. basalt wool, biosil wool, glass wool, E-type wool, etc.);
Binder material specifications (if applicable);
Average fibre dimensions (thickness, length);
(e) Minimum bulk material packing density (kg/m );
(f)
Maximum contact surface between the gas flow and the absorbing material
(e.g. perforation open area).
3. APPLICATION FOR APPROVAL
3.1. The application for approval of a vehicle type with regard to noise shall be submitted by its
manufacturer or by his duly accredited representative.
3.2. It shall be accompanied by the undermentioned documents and the following particulars in
triplicate:
3.2.1. a description of the vehicle type with regard to the items mentioned in Paragraph 2.2.
above. The numbers and/or symbols identifying the engine type and the vehicle type shall be
specified;
3.2.2. a list of the components, duly identified, constituting the noise reduction system;

5.2. An approval number shall be assigned to each type approved. Its first two digits (at present 02
corresponding to the 02 series of amendments which entered into force on April 18, 1995) shall
indicate the series of amendments incorporating the most recent major technical amendments
made to the Regulation at the time of issue of the approval. The same Contracting Party may
not assign the same number to the same vehicle type equipped with another type of noise
reduction system or to another vehicle type.
5.3. Notice of approval or of extension or of refusal or withdrawal of approval or of production
definitively discontinued of a vehicle type pursuant to this Regulation shall be communicated to
the Parties to the Agreement applying this Regulation, by means of a form conforming to the
model in Annex 1 to this Regulation.
5.4. There shall be affixed, conspicuously and in a readily accessible place specified on the
approval form, to every vehicle conforming to a vehicle type approved under this Regulation an
international approval mark consisting of:
5.4.1. a circle surrounding the Letter "E" followed by the distinguishing number of the country which
has granted approval ;
5.4.2. the number of this Regulation, followed by the Letter "R", a dash and the approval number to
the right of the circle prescribed in Paragraph 5.4.1.
5.5. If the vehicle conforms to a vehicle type approved, under one or more other Regulations
annexed to the Agreement, in the country which has granted approval under this Regulation,
the symbol prescribed in Paragraph 5.4.1. need not be repeated; in such a case the regulation
and approval numbers and the additional symbols of all the Regulations under which approval
has been granted in the country which has granted approval under this Regulation shall be
placed in vertical columns to the right of the symbol prescribed in Paragraph 5.4.1.
5.6. The approval mark shall be clearly legible and be indelible.
5.7. The approval mark shall be placed close to or on the vehicle data plate affixed by the
manufacturer.
5.8. Annex 2 to this Regulation gives examples of arrangements of the approval mark.

6.2.2. Sound level limits
6.2.2.1. Subject to the provisions of Paragraph 6.2.2.2. below, the sound level of vehicle types, as
measured by the method described in Paragraph 3.1. of Annex 3 to this Regulation, shall not
exceed the following limits:
Vehicle categories
Limit values
(dB(A))
6.2.2.1.1. Vehicles used for the carriage of passengers and capable of having not
more than nine seats, including the driver's seat 74
6.2.2.1.2.
Vehicles used for the carriage of passengers having more than nine seats,
including the driver's seat, and a maximum authorized mass of more than
3.5 t
6.2.2.1.2.1.
with an engine power less than 150 kW (ECE)
78
6.2.2.1.2.2.
with an engine power of 150 kW (ECE) or above
80
6.2.2.1.3.
Vehicles used for the carriage of passengers having more than nine seats,
including the driver's seat; vehicles used for the carriage of goods
6.2.2.1.3.1.
with a maximum authorized mass not exceeding 2 t
76
6.2.2.1.3.2.
with a maximum authorized mass greater than 2 t but not exceeding 3.5 t
77
6.2.2.1.4.
Vehicles used for the transport of goods with a maximum authorized mass
exceeding 3.5 t
6.2.2.1.4.1.
with an engine power less than 75 kW (ECE)
77
6.2.2.1.4.2.
with an engine power of 75 kW (ECE) or above but less than 150 kW
(ECE)
78
6.2.2.1.4.3.
with an engine power of 150 kW (ECE) or above
80
6.2.2.2. However,
6.2.2.2.1. For the vehicle types mentioned in Paragraphs 6.2.2.1.1. and 6.2.2.1.3. equipped with a
compression-ignition and direct-injection internal combustion engine, the limit values shall
be increased by 1 dB(A);
6.2.2.2.2.
For vehicle types designed for off-road
use and with a maximum authorised mass above
2 t, the limit values shall be increased:
6.2.2.2.2.1. by 1 dB(A) if they are equipped with an engine having a power of less than 150 kW (ECE);
6.2.2.2.2.2. by 2 dB(A) if they are equipped with an engine having a power of 150 kW (ECE) or above.
6.2.2.2.3. For vehicle types mentioned in Paragraph 6.2.2.1.1. fitted with a gear box having more than
four forward gears and equipped with an engine developing a maximum power greater than
140 kW (ECE) and having a maximum-power/maximum-mass ratio grater than 75 kW/t, the
limit values shall be increased by 1 dB(A), if the speed at which the rear of the vehicle
passes the Line BB' in third gear is greater than 61 km/h.

8.4. The competent authority which has granted type-approval may at any time verify the
conformity control method applicable to each production unit.
8.4.1. In every inspection the test books and production survey records shall be presented to the
visiting inspector.
8.4.2. The inspector may take samples at random which will be tested in the manufacturer's
laboratory. The minimum number of samples may be determined according to the results of
the manufacturer's own verification.
8.4.3. When the quality level appears unsatisfactory or when it seems necessary to verify the
validity of the tests carried out in application of Paragraph 8.4.2. the inspector shall select
samples to be sent to the technical service which has conducted the type approval tests.
8.4.4. The competent authority may carry out any test prescribed in this Regulation.
8.4.5. The normal frequency of inspections by the competent authority shall be one every two
years. If unsatisfactory results are recorded during one of these visits, the competent
authority shall ensure that, all necessary steps are taken to re-establish the conformity of
production as rapidly as possible.
9. PENALTIES FOR NON-CONFORMITY OF PRODUCTION
9.1. The approval granted in respect of a vehicle type pursuant to this Regulation may be
withdrawn if the requirements set forth above are not met.
9.2. If a Contracting Party to the Agreement applying this Regulation withdraws an approval it
has previously granted, it shall forthwith so notify the other Contracting Parties applying this
Regulation, by means of a communication form conforming to the model in Annex 1 to this
Regulation.
10. PRODUCTION DEFINITIVELY DISCONTINUED
10.1. If the holder of the approval completely ceases to manufacture a vehicle type approved in
accordance with this Regulation, he shall so inform the authority which granted the
approval. Upon receiving the relevant communication that authority shall inform thereof the
other Parties to the 1958 Agreement applying this Regulation by means of a communication
form conforming to the model in Annex 1 to this Regulation.
11. TRANSITIONAL PROVISIONS
11.1. As from the official date of entry into force of the 02 series of amendments, no Contracting
Party applying this Regulation shall refuse to grant ECE approval under this Regulation as
amended by the 02 series of amendments.
11.2. As from October 1, 1995, Contracting Parties applying this Regulation shall grant
ECE approvals only if the vehicle type to be approved meets the requirements of this
Regulation as amended by the 02 series of amendments.
11.3. As from October 1, 1996, Contracting Parties applying this Regulation may refuse first
national registration (first entry into service) of a vehicle which does not meet the
requirements of the 02 series of amendments to this Regulation.

ANNEX 1
(Maximum format: A4 (210 × 297 mm) )
COMMUNICATION
issued by:
Name of administration:
.............................................
.............................................
.............................................
concerning:
APPROVAL GRANTED
APPROVAL EXTENDED
APPROVAL REFUSED
APPROVAL WITHDRAWN
PRODUCTION DEFINITIVELY DISCONTINUED
of a vehicle type with regard to its noise emission pursuant to ECE Regulation No. 51
Approval No. .................................................. Extension No. ................................
1. Trade name or mark of the vehicle ............................................................................................
2. Vehicle type ................................................................................................................................
2.1. Maximum permissible mass including semi-trailer (where applicable) ......................................
...................................................................................................................................................
3. Manufacturer's name and address ............................................................................................
4. If applicable, name and address of manufacturer's representative ...........................................
...................................................................................................................................................
5. Engine:
5.1. Manufacturer: .............................................................................................................................
5.2. Type: .........................................................................................................................................
5.3. Model: .......................................................................................................................................
5.4. Rated maximum power (ECE): ............................... kW at ......................................... rev/min

8.1. Sound Level of Moving Vehicle:
First measurement
Second measurement
Third measurement
Fourth measurement
MEASUREMENT RESULTS
Left-hand side
dB(a)
Right-hand side
dB(A)
Position of
gear lever
Test result: ............................................................................................... dB(A)
8.2. Sound Level of Stationary Vehicle:
Position and Orientation of Microphone (According to Diagrams in Appendix of Annex 3)
First measurement
Second measurement
Third measurement
MEASUREMENT RESULTS
dB(A)
Engine speed
Test result: ............................................................................................... dB(A)
8.3. Sound Level of Compressed Air Noise:
First measurement
Second measurement
Third measurement
Fourth measurement
MEASUREMENT RESULTS
Left-hand side
dB(A)
Right-hand side
dB(A)
Test result: ................................................................................................ dB(A)

ANNEX 2
ARRANGEMENTS OF THE APPROVAL MARK
Model A
(See Paragraph 5.4. of this Regulation)
a = 8 mm min.
The above approval mark affixed to a vehicle shows that the vehicle type concerned has, with regard to
its noise emission, been approved in the Netherlands (E 4) pursuant to Regulation No. 51 under approval
No. 022439. The first two digits of the approval number indicate that Regulation No. 51 already included
the 02 series of amendments when the approval was granted.
Model B
(See Paragraph 5.5. of this Regulation)
a = 8 mm min.
The above approval mark affixed to a vehicle shows that the vehicle type concerned has been approved
in the Netherlands (E 4) pursuant to Regulations Nos. 51 and 33. The approval numbers indicate that,
at the dates when the respective approvals were granted, Regulation No. 51 included the 02 series of
amendments while Regulation No. 33 was in its original form.

2. CONDITIONS OF MEASUREMENT
2.1. Site
2.1.1. The test site shall consist of a central acceleration section surrounded by a substantially flat
test area.
The test track shall be such that the conditions of a free sound field between the sound
source and the microphone are attained to within 1 dB. This condition shall be deemed to
be met if there are no large sound-reflecting objects such as fences, rocks, bridges or
building within 50 m of the centre of the acceleration section. The surface of the site shall
be in accordance with the provisions given in Annex 8 to this Regulation or in accordance to
ISO 10844:2011 and be free of powdery snow, tall grass, loose soil or cinders.
There shall be no obstacle which could affect the sound field within the vicinity of the
microphone and the sound source. The observer carrying out the measurements must so
position himself as not to affect the readings of the measuring instrument.
2.1.2. Measurements shall not be made under adverse weather conditions. It must be ensured
that the results are not affected by gusts of wind.
Any sound peak which appears to be unrelated to the characteristics of the general sound
level of the vehicle shall be ignored in taking the readings.
2.1.2.1. The meteorological instrumentation should be positioned adjacent to the test area at a
height of 1.2 ± 0.1 m.
The measurements shall be made when the ambient air temperature is within the range
from 0° C to 40° C.
Tests shall not be carried out if the wind speed, including gusts, at microphone height
exceeds 5 m/s, during the sound measurement interval and shall be recorded during each
test run.
Values representative of temperature, wind speed and direction, relative humidity, and
barometric pressure shall be recorded during the sound measurement interval.
2.1.3. The A-weighted sound level of sound sources other than those of the vehicle to be tested
and of wind effects must be at least 10 dB(A) below the sound level produced by the
vehicle.
2.2. Vehicle
2.2.1. Measurements shall be made on unladen vehicles and, except in the case of non-separable
vehicles, without trailer or semi-trailer.
2.2.2. The tyres used for the test are selected by the vehicle manufacturer and shall comply with
commercial practice and be available on the market; they shall correspond to one of the tyre
sizes designated for the vehicle by the vehicle manufacturer and meet the minimum tread
depth of 1.6 mm in the main grooves of the tread surface.
The tyres must be inflated to the pressure(s) appropriate to the test mass of the vehicle.

3.1.2.
Determination of the Approach Speed
3.1.2.1.
Symbols used
The letter symbols used in this Paragraph have the following meaning:
S :
engine rotation speed as indicated under Item 5.4. of Annex 1.
N :
V :
V
uniform engine rotational speed at the approach of Line AA'.
uniform vehicle speed at the approach of Line AA'.
: maximum speed declared by the vehicle manufacturer.
3.1.2.2. Vehicle with no gearbox
For vehicles with no gearbox or with no transmission control, the uniform speed at the
approach of Line AA' will be such that:
either
or
V = 50 km/h;
V corresponding to N = 3/4 S and
V ≤ 50 km/h
in the case of vehicles of Category M and in the case of vehicles of categories other than
M , having an engine power not greater than 225 kW (ECE);
or
V corresponding to N = 1/2 S and
V ≤ 50 km/h
in the case of vehicles not belonging to Category M having an engine power greater than
225 kW (ECE);
or, in the case of vehicles powered by an electric motor
whichever is the lower.
3
V = V or V =
4
3.1.2.3. Vehicle with a manually-operated gearbox
3.1.2.3.1. Approach speed
50 km / h,
The vehicle shall approach the Line AA' at a steady speed with a tolerance ± 1 km/h; except
where the controlling factor is engine speed the tolerance shall be the larger of ± 2% or
± 50 min , such that:
either
V = 50 km/h;

3.1.2.3.2.3. Vehicles of categories other than M and N in which the total number of forward gear ratios
is x (including those obtained by way of an auxiliary transmission or a multi-gear axle) will
be tested sequentially, using the ratio equal to or higher than x/n.
Initial testing will be carried out using the ratio which is gear (x/n) or the next higher gear
ratio if (x/n) is not an integer. The testing shall continue from the gear (x/n) to the next
higher gear.
Shifting up gear ratios from (x/n) shall be terminating when in the gear X in which the rated
engine speed is reached just before the rear of the vehicle has passed the Line BB'.
Sample Calculation for Testing: There are 16 forward ratios for drive train having a
transmission with 8 gears and an auxiliary transmission with 2 gears. If the engine has
230 kW then (x/n) = (8 × 2)/3 = 16/3 = 5 1/3. The initial test gear ratio is 6th (includes the
gears from both the main transmission and auxiliary which is 6th out of the 16 total gear
ratios), with the next gear ratio is 7th up to ratio X.
In the case of vehicles having different overall gear ratios the representative of the vehicle
type by the test vehicle is determined as follows:
if the highest sound level is obtained between the ratio x/n and ratio X the vehicle shall be
deemed representative of its type;
if the highest sound level is obtained at ratio x/n the vehicle selected shall be deemed
representative of its type only for those vehicles which have a lower overall gear ratio at x/n;
if the highest sound level is obtained at ratio X the vehicle selected shall be deemed
representative of its type only for those vehicles which have a higher overall gear ratio than
the gear ratio X.
However the vehicle is deemed representative of its type also, if at the applicant's request
the tests are extended over more ratios than foreseen, and the highest sound level is
obtained between the extreme ratios tested.
3.1.2.4. Automatic transmission
3.1.2.4.1. Vehicles without a manual selector
3.1.2.4.1.1. Approach speed
The vehicle shall approach the Line AA' at various uniform speeds of 30, 40, 50 km/h or at
3/4 of the maximum on-road speed if this value is lower.
If the vehicle is equipped with an automatic transmission which cannot be tested with the
procedure outlined in the subsequent sections, it shall be tested at different approach
speeds, namely 30 km/h, 40 km/h, and 50 km/h, or at 3/4 of maximum vehicle speed as
specified by the manufacturer if this value is lower. The condition giving the highest noise
level shall be retained.

3.1.2.4.2.4. Prevention of Downshift
Some vehicles equipped with an automatic transmission (two or more discrete ratios) may
downshift to a gear ratio not normally used in urban driving, as defined by the
manufacturer. A gear ratio not used for urban driving includes a gear ratio intended for slow
movement, parking or braking. In these cases the operator may select any of the following
modifications:
(a)
increase the vehicle speed v to a maximum of 60 km/h in order to avoid such a
change down;
(b) maintain the vehicle speed v at 50 km/h and limit the fuel supply to the engine to 95%
of the supply necessary for full load; this condition is considered to be satisfied;
(i)
(ii)
in the case of a spark-ignition engine, when the angle of the throttle opening is
90% of the full angle,
in the case of a compression-ignition engine, when the fuel supply to the
injection pump is limited to 90% of its maximum supply;
(c)
establish and use an electronic control that will prevent a downshift to gears lower
than those used in normal urban driving as defined by the manufacturer.
3.1.3 Interpretation of Results
The measurement of noise emitted by the vehicle in motion shall be considered valid if the
difference between the two consecutive measurements on the same side of the vehicle is
not more than 2 dB(A).
The figure recorded shall be that corresponding to the highest sound level. Should that
figure exceed by more than 1 dB(A) the maximum sound level authorised for the category of
vehicle tested, a second series of two measurements at the corresponding microphone
position shall be made. Three out of the four results so obtained in this second position must
fall within the prescribed limits.
To allow for lack of precision in the measuring instrument the figures read from it during
measurement shall each be reduced by 1 dB(A).
3.2. Measurement of Noise Emitted by Stationary Vehicles
3.2.1. Sound Level in the Vicinity of Vehicles
In order to facilitate subsequent checks on vehicles in use, the sound level must be
measured close to the exhaust system outlet in accordance with the following requirements
and the measurement results entered in the test report drawn up for the purpose of issuing
the certificate referred to in Annex 1.

3.2.5.3.1. Microphone Orientation
3.2.5.3.1.1. The microphone shall be located at a distance of 0.5 m ± 0.01 m from the reference point of
the exhaust pipe defined in Figure 2 and at an angle of 45° (± 5°) to the vertical plane
containing the flow axis of the pipe termination. The microphone shall be at the height of
the reference point, but not less than 0.2 m from the ground surface. The reference axis of
the microphone shall lie in a plane parallel to the ground surface and shall be directed
towards the reference point on the exhaust outlet.
If two microphone positions are possible, the location farthest laterally from the vehicle
longitudinal centreline shall be used.
If the flow axis of the exhaust outlet pipe is at 90° to the vehicle longitudinal centreline, the
microphone shall be located at the point, which is furthest from the engine.
3.2.5.3.1.2. For vehicles having an exhaust provided with outlets spaced more than 0.3 m apart, one
measurement is made for each outlet as if it were the only one, and the highest sound
pressure level shall be noted.
3.2.5.3.1.3. If a vehicle has two or more exhaust outlets spaced less than 0.3 m apart and connected to
a single silencer, only one measurement shall be made. The microphone shall be located
relative to the outlet farthest from the vehicle longitudinal centreline, or when such outlet
does not exist, to the outlet, which is highest above the ground.
3.2.5.3.1.4. For vehicles with a vertical exhaust (e.g. commercial vehicles) the microphone shall be
placed at the height of the exhaust outlet. Its axis shall be vertical and oriented upwards. It
shall be placed at a distance of 0.5 m ± 0.01 m from the exhaust pipe reference point as
defined in Figure 2, but never less than 0.2 m from the side of the vehicle nearest to the
exhaust.
3.2.5.3.1.5. For vehicles, where the reference point of the exhaust pipe is not accessible, or located
under the vehicle body, as shown in Figures 3b and 3c, because of the presence of
obstacles which form part of the vehicle (e.g. spare wheel, fuel tank, battery compartment),
the microphone shall be located at least 0.2 m from the nearest obstacle, including the
vehicle body, and its axis of maximum sensitivity shall face the exhaust outlet from the
position least concealed by the above mentioned obstacles.
When several positions are possible, as shown in Figure 3c, the microphone position giving
the lowest value of d1 or d2 shall be used.
Note: Figures 3a to 3d show examples of the position of the microphone, depending on
the location of the exhaust pipe.

ANNEX 3 - APPENDIX
MEASURING POSITIONS FOR VEHICLES IN MOTION
Figure 1
Measuring Positions for Stationary Vehicles (Examples)

Figure 3a
Figure 3b
Figure 3c
Figure 3d

3.
Category N
Power-driven vehicles having at least four wheels and used for the carriage of
goods
3.1. Category N : Vehicles used for the carriage of goods and having a maximum mass not
exceeding 3.5 t.
3.2. Category N : Vehicles used for the carriage of goods and having a maximum mass
exceeding 3.5 t but not exceeding 12 t.
3.3. Category N : Vehicles used for the carriage of goods and having a maximum mass
exceeding 12 t.
3.4. Remarks
3.4.1. In the case of a towing vehicle designed to be coupled to a semi-trailer (tractor for
semi-trailer), the mass to be considered for classifying the vehicle is the mass of the tractor
vehicle in running trim, increased by the mass corresponding to the maximum static vertical
load transferred to the tractor vehicle by the semi-trailer and, where applicable, by the
maximum mass of the tractor vehicle's own load.
3.4.2. The equipment and installations carried on certain special-purpose vehicles (crane vehicles,
workshop vehicles, publicity vehicles, etc.) are regarded as being equivalent to goods.

1.2.3. During each six-hour period, the engine shall be run, under the following conditions:
(a)
(b)
(c)
(d)
(e)
(f)
Five minutes at idling speed;
One-hour sequence under ¼ load at ¾ of rated maximum speed (S);
One-hour sequence under ½ load at ¾ of rated maximum speed (S);
10-minute sequence under full load at ¾ of rated maximum speed (S);
15-minute sequence under ½ load at rated maximum speed (S);
30-minute sequence under ¼ load at rated maximum speed (S).
Each period shall comprise two sequenced sets of the six above-mentioned conditions in
consecutive order from (a) to (f).
1.2.4. During the test, the silencing system or components thereof shall not be cooled by a forced
draught simulating normal airflow around the vehicle. Nevertheless, at the request of the
manufacturer, the silencing system or components thereof may be cooled in order not to
exceed the temperature recorded at its inlet when the vehicle is running at maximum speed.
1.3. Conditioning by Pulsation
1.3.1. The silencing system or components thereof shall be fitted to the vehicle referred to in
Paragraph 3.3 of this Regulation or the engine referred to in Paragraph 3.4 of this
Regulation. In the former case the vehicle shall be mounted on a roller dynamometer.
In the second case, the engine shall be mounted on a dynamometer. The test apparatus, a
detailed diagram of which is shown in Figure 3 of the Appendix to this Annex shall be fitted
at the outlet of the silencing system. Any other apparatus providing equivalent results is
acceptable.
1.3.2. The test apparatus shall be adjusted in a such a way that the exhaust-gas flow is
alternatively interrupted and re-established by the quick-action valve for 2 500 cycles.
1.3.3. The valve shall open when the exhaust-gas back pressure, measured at least 100 mm
downstream of the intake flange, reaches a value of between 35 and 40 kPa. It shall close
when this pressure does not differ by more than 10% from its stabilised value with the valve
open.
1.3.4. The time-delay switch shall be set for the duration of gas exhaust resulting from the
provisions laid down in Paragraph 1.3.3 above.
1.3.5. Engine speed shall be 75% of the speed (S) at which the engine develops maximum power.
1.3.6. The power indicated by the dynamometer shall be 50% of the full-throttle power measured
at 75% of engine speed (S).
1.3.7. Any drain holes shall be closed off during the test.
1.3.8. The entire test shall be completed within 48 hours.
If necessary, one cooling period will be observed after each hour.

ANNEX 6
COMPRESSED AIR NOISE
1. METHOD OF MEASUREMENT
The measurement is performed at microphone position 2 and 6 according to Figure 1, with
the vehicle stationary. The highest A-weighted noise level is registered during venting the
pressure regulator and during ventilating after the use of both the service and parking
brakes.
The noise during venting the pressure regulator is measured with the engine at idling speed.
The ventilating noise is registered while operating the service and parking brakes; before
each measurement, the air-compressor unit has to be brought up to the highest permissible
operating pressure, and then the engine switched off.
2. EVALUATION OF THE RESULTS
For all microphone positions two measurements are taken. In order to compensate for
inaccuracies of the measuring equipment, the meter reading is reduced by 1 dB(A), and the
reduced value is taken as the result of measurement. The results are taken as valid if the
difference between the measurements as one microphone position does not exceed
2 dB(A). The highest value measured is taken as the result. If this value exceeds the noise
limit of 1 dB(A), two additional measurements are to be taken at the corresponding
microphone position.
In this case, three out of the four results of measurement obtained at this position have to
comply with the noise limit.
3. LIMITING VALUE
The sound level shall not exceed the limit of 72 dB(A).

ANNEX 7
CHECKS ON CONFORMITY OF PRODUCTION
1. GENERAL
These requirements are consistent with the test to be held to check conformity of production
according to Paragraphs 8.3.5. and 8.4.3. of this Regulation.
2. TESTING PROCEDURE
The test site and measuring instruments shall be those as described in Annex 3.
2.1. The vehicle(s) under test shall be subjected to the test for measurement of noise of vehicle
in motion as described in Paragraph 3.1. of Annex 3.
2.2. Compressed Air Noise
Vehicles having maximum mass exceeding 2 800 kg and equipped with compressed air
systems must be subjected to an additional test for measurement of the compressed air
noise as described in Paragraph 1 of Annex 6.
3. SAMPLING
One vehicle has to be chosen. If after the test of Paragraph 4.1. the vehicle is not
considered to conform to the requirements of this Regulation, two more vehicles have to be
tested.
4. EVALUATION OF THE RESULTS
4.1. If the sound level of the vehicle tested pursuant to Paragraphs 1 and 2 does not exceed by
more than 1 dB(A) the limit value prescribed in Paragraph 6.2.2. of this Regulation, for
measurement according to Paragraph 2.1. above, and in Paragraph 3 of Annex 6 to this
Regulation, for measurement according to Paragraph 2.2. above, the vehicle type shall be
considered to conform to the requirements of this Regulation.
4.2. If the vehicle tested according to Paragraph 4.1. does not satisfy the requirements laid down
in that Paragraph, two more vehicles of the same type have to be tested pursuant to
Paragraphs 1 and 2.
4.3. If the sound level of the second and/or third vehicle of Paragraph 4.2. exceeds by more than
1 dB(A) the limit values prescribed in Paragraph 6.2.2. of this Regulation, the vehicle type
shall be considered not to conform to the requirements of this Regulation and the
manufacturer shall take the necessary measures to re-establish the conformity.

2.5. Period of Testing
In order to check whether the surface continues to conform to the texture and voids content
or sound absorption requirements stipulated in this standard, periodic testing of the surface
shall be done at the following intervals:
(a)
For residual voids content or sound absorption:
when the surface is new;
if the surface meets the requirements when new, no further periodical testing is
required. If it does not meet the requirement when it is new, it may do later because
surfaces tend to become clogged and compacted with time.
(b)
For texture depth (TD):
when the surface is new;
when the noise testing starts (NB: not before four weeks after laying);
then every twelve months.
3. TEST SURFACE DESIGN
3.1. Area
When designing the test track layout it is important to ensure that, as a minimum
requirement, the area traversed by the vehicles running through the test strip is covered with
the specified test material with suitable margins for safe and practical driving. This will
require that the width of the track is at least 3 m and the length of the track extends beyond
Lines AA and BB by at least 10 m at either end. Figure 1 shows a plan of a suitable test
side and indicates the minimum area which shall be machine laid and machine compacted
with the specified test surface material. According to Annex 3, Paragraph 3.1.1.1.,
measurements have to be made on each side of the vehicle. This can be made either by
measuring with two microphone locations (one on each side of the track) and driving in one
direction, or measuring with a microphone only on one side of the track but driving the
vehicle in two directions. If the latter method is used, then there are no surface
requirements on that side of the track where there is no microphone.

3.2.2. Design Guidelines
As a guide to the surface constructor, an aggregate grading curve which will give desired
characteristics is shown in Figure 2. In addition. Table 1 gives some guidelines in order to
obtain the desired texture and durability. The grading curve fits the following formula:
P (% passing) = 100 . (d/d )
where:
d
=
square mesh sieve size, in mm
d
=
8 mm for the mean curve
d
=
10 mm for the lower tolerance curve
d
=
6.3 mm for the upper tolerance curve
Figure 2
Grading Curve of the Aggregate in the Asphaltic Mix with Tolerances
In addition to the above, the following recommendations are given:
(a)
(b)
(c)
The sand fraction (0.063 mm < square mesh sieve size < 2 mm) shall include no
more than 55% natural sand and at least 45% crushed sand;
The base and sub-base shall ensure a good stability and evenness, according to best
road construction practice;
The chippings shall be crushed (100% crushed faces) and of a material with a high
resistance to crushing;

The residual voids content has to be determined for each core, then the average value from
all cores shall be calculated and compared with the requirement of Paragraph 2.1. In
addition, no single core shall have a voids value which is higher than 10%. The test surface
constructor is reminded of the problem which may arise when the test area is heated by
pipes or electrical wires and cores must be taken from this area. Such installations must be
carefully planned with respect to future core drilling locations. It is recommended to leave a
few locations of size approximately 200 × 300 mm where there are no wires/pipes or where
the latter are located deep enough in order not to be damaged by cores taken from the
surface layer.
4.2. Sound Absorption Coefficient
The sound absorption coefficient (normal incidence) shall be measured by impedance tube
method using the procedure specified in ISO 10534-1: "Acoustic – Determination of sound
absorption coefficient and impedance by a tube method."
Regarding test specimens, the same requirements shall be followed as regarding the
residual voids content (see Paragraph 4.1.). The sound absorption shall be measured in the
range between 400 Hz and 800 Hz and in the range between 800 Hz and 1,600 Hz (at least
at the centre frequencies of their octave bands) and the maximum values shall be identified
for both of these frequency ranges. Then these values, for all test cores, shall be averaged
to constitute the final result.
4.3. Volumetric Macrotexture Measurement
For the purpose of this standard, texture depth measurements shall be made on at least
10 positions evenly spaced along the wheel tracks of the test strip and the average value
taken to compare with the specified minimum texture depth. See ISO 10844:1994 for the
description of the procedure.
5. STABILITY IN TIME AND MAINTENANCE
5.1. Age Influence
In common with any other surfaces, it is expected that the tyre/road noise level measure on
the test surface may increase slightly during the first 6-12 months after construction.
The surface will achieve its required characteristics not earlier than four weeks after
construction. The influence of age on the noise from trucks is generally less than that from
cars.
The stability over time is determined mainly by the polishing and compaction by vehicles
driving on the surface. It shall be periodically checked as stated in Paragraph 2.5.
5.2. Maintenance of the Surface
Loose debris or dust which could significantly reduce the effective texture depth must be
removed from the surface. In countries with winter climates, salt is sometimes used for
de-icing. Salt may alter the surface temporarily or even permanently in such a way as to
increase noise and is therefore not recommended.

ANNEX 9
VEHICLE AND TEST DATA PURSUANT TO MEASUREMENT METHOD B
Information reported in Annex 1 need not to be repeated
1. Trade name or mark of the vehicle ...........................................................................................
2. Vehicle type ...............................................................................................................................
2.1. Maximum mass including semi-trailer (where applicable) ........................................................
...................................................................................................................................................
3. Manufacturer's name and address ...........................................................................................
4. If applicable, name and address of manufacturer's representative ..........................................
...................................................................................................................................................
5. Engine:
5.1. Manufacturer: ............................................................................................................................
5.2. Type: .........................................................................................................................................
5.3. Model: .......................................................................................................................................
5.4. Rated maximum power (ECE): .............. kW at ...................... min (rpm)
5.5. Kind of engine: e.g. positive-ignition, compression ignition, etc
...................................................................................................................................................
5.6. Cycles: two stroke or four-stroke (if applicable) ........................................................................
5.7. Cylinder capacity (if applicable) ................................................................................................
6. Transmission: non-automatic gearbox/automatic gearbox
6.1. Number of gears .......................................................................................................................
7. Equipment:
7.1. Exhaust silencer: .......................................................................................................................
7.1.1. Manufacturer or authorised representative (if any) ...................................................................
7.1.2. Model: .......................................................................................................................................
7.1.3. Type: ............ in accordance with drawing No.: ....................

8.5. Noise level of stationary vehicle:
Position and orientation of microphone (according to Figure 2 in Appendix of Annex 3)
Test result for stationary test: ...........
dB(A)
8.6. Noise level of compressed air sound:
Test result for
(a) service brake: ............................................................ dB(A)
(b) parking brake: ............................................................ dB(A)
(c) during the pressure regulator actuation: ..................... dB(A)
9. Vehicle submitted for approval on: ............................................................................................
10. Technical service responsible for type-approval tests: .............................................................
...................................................................................................................................................
11. Date of test report issued by that service: ................................................................................
12. Number of test report issued by that service: ...........................................................................
13. Position of approval mark on the vehicle ..................................................................................
14. Place ........................................................................................................................................
15. Date ...........................................................................................................................................
16. Signature ...................................................................................................................................
17. The following documents, bearing the approval number shown above, are annexed to this
document: .................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
drawings and/or photographs, diagrams and plans of the engine and of the noise reduction
system;
list of components, duly identified constituting the noise reduction system.
18. Reason for extension of approval: ............................................................................................
19. Remarks ....................................................................................................................................

1.5. Meteorological Instrumentation
The meteorological instrumentation used to monitor the environmental conditions during
the test shall include the following devices, which meet at least the given accuracy:
(a) temperature measuring device, ± 1° C;
(b)
(c)
wind speed-measuring device, ± 1.0 m/s;
barometric pressure measuring device, ± 5 hPa;
(d) a relative humidity measuring device, ± 5%.
2. CONDITIONS OF MEASUREMENT
2.1. Test Site and Ambient Conditions
The test site shall be substantially level. The surface of the test track shall be dry. The
test site shall be such that when a small omni-directional noise source is placed on its
surface at the central point (intersection of the microphone Line PP' and the centreline of
the vehicle lane CC'), deviations from hemispherical acoustic divergence shall not
exceed ± 1 dB.
This condition is deemed to be satisfied if the following requirements are met:
(a)
(b)
(c)
Within a radius of 50 m from the centre of the track the space is free of large
reflecting objects such as fences, rocks, bridges or buildings.
The test track and the surface of the site are dry and free from absorbing materials
such as powdery snow, or loose debris.
In the vicinity of the microphone, there are no obstacle that could influence the
acoustical field and no person is positioned between the microphone and the
noise source. The meter observer is positioned so as not to influence the meter
reading.
Measurements shall not be made under adverse weather conditions. It must be ensured
that the results are not affected by gusts of wind.
The meteorological instrumentation should be positioned adjacent to the test area at a
height of 1.2 m ± 0.02 m. The measurements shall be made when the ambient air
temperature is within the range from 5° C to 40° C.
The tests shall not be carried out if the wind speed, including gusts, at microphone height
exceeds 5 m/s, during the noise measurement interval.
A value representative of temperature, wind speed and direction, relative humidity, and
barometric pressure shall be recorded during the noise measurement interval.
Any noise peak which appears to be unrelated to the characteristics of the general noise
level of the vehicle shall be ignored in taking the readings.

2.2.2. The tyres to be used for the test shall be representative for the vehicle and shall be
selected by the vehicle manufacturer and recorded in Annex 9. They shall correspond to
one of the tyre sizes designated for the vehicle as original equipment. The tyre is or will
be commercially available on the market at the same time as the vehicle . The tyres
shall be inflated to the pressure recommended by the vehicle manufacturer for the test
mass of the vehicle. The tyres shall have a tread depth of at least 80% of the full tread
depth.
2.2.3. Before the measurements are started, the engine shall be brought to its normal operating
conditions.
2.2.4. If the vehicle is fitted with more than two-wheel drive, it shall be tested in the drive which
is intended for normal road use.
2.2.5. If the vehicle is fitted with fan(s) having an automatic actuating mechanism, this system
shall not be interfered with during the measurements.
2.2.6. If the vehicle is equipped with an exhaust system containing fibrous materials, the
exhaust system is to be conditioned before the test according to Annex 5.
3. METHODS OF TESTING
3.1. Measurement of Noise of Vehicles in Motion
3.1.1. General Conditions of Test
Two Lines, AA' and BB', parallel to Line PP' and situated respectively 10 m forward and
10 m rearward of Line PP' shall be marked out on the test runway
At least four measurements shall be made on each side of the vehicle and for each gear.
Preliminary measurements may be made for adjustment purposes, but shall be
disregarded.
The microphone shall be located at a distance of 7.5 m ± 0.05 m from the reference
Line CC' of the track and 1.2 m ± 0.02 m above the ground.
The reference axis for free field conditions (see IEC 61672-1:2002) shall be horizontal
and directed perpendicularly towards the path of the vehicle Line CC'.

3.1.2.1.2.2. Calculation procedure for vehicles with automatic transmissions, adaptive transmissions
and CVT’s tested with non-locked gear ratios:
a used in the determination of gear selection shall be the average of the four
a during each valid measurement run.
If devices or measures described in Paragraph 3.1.2.1.4.2., can be used to control
transmission operation for the purpose of achieving test requirements, calculate a
using the equation:
a = ((v /3.6)² – (v /3.6)²) / (2 × (20+l))
Pre-acceleration may be used.
If no devices or measures described in Paragraph 3.1.2.1.4.2. are used, calculate a
using the equation:
a = ((v /3.6)² – (v /3.6)²) / (2 × (10+l))
Pre-acceleration shall not be used.
The location of depressing the accelerator shall be where the reference point of the
vehicle passes Line AA'.
3.1.2.1.2.3. Target Acceleration
The target acceleration a defines the typical acceleration in urban traffic and is
derived from statistical investigations. It is a function depending on the PMR of a
vehicle.
The target acceleration a is defined by:
a = 0.63 × log (PMR) – 0.09
3.1.2.1.2.4. Reference Acceleration
The reference acceleration a defines the required acceleration during the
accelerated test on the test track. It is a function depending on the power-to-mass ratio
of a vehicle. That function is different for specific vehicle categories.
The reference acceleration a is defined by:
a = 1.59 × log (PMR) – 1.41 for PMR ≥ 25
a = a = 0.63 × log (PMR) – 0.09 for PMR < 25
3.1.2.1.3. Partial Power Factor k
The partial power factor k (see Paragraph 3.1.3.1.) is used for the weighted combination
of the test results of the acceleration test and the constant speed test for vehicles of
Category M and N .
In cases other than a single gear test a
has to be used instead of a a
(see
Paragraph 3.1.3.1.).

Therefore, it is permitted to establish and use electronic or mechanical devices, including
alternate gear selector positions, to prevent a downshift to a gear ratio which is typically
not used at the specified test condition in urban traffic.
The achieved acceleration a shall be greater or equal to a .
If possible, the manufacturer shall take measures to avoid an acceleration value a
greater than 2.0 m/s .
The achieved acceleration a is then used for the calculation of the partial power
factor k (see Paragraph 3.1.2.1.3.) instead a .
3.1.2.1.5. Acceleration Test
The manufacturer shall define the position of the reference point in front of Line AA' of
fully depressing the accelerator. The accelerator shall be fully depressed (as rapidly as
is practicable) when the reference point of the vehicle reaches the defined point. The
accelerator shall be kept in this depressed condition until the rear of the vehicle reaches
Line BB'. The accelerator shall then be released as rapidly as possible. The point of
fully depressing the accelerator shall be reported in the vehicle and test data (Annex 9).
The technical service shall have the possibility of pretesting.
In the case of articulated vehicles consisting of two non-separable units regarded as a
single vehicle, the semi-trailer shall be disregarded in determining when Line BB' is
crossed.
3.1.2.1.6. Constant Speed Test
The constant speed test shall be carried out with the same gear(s) specified for the
acceleration test and a constant speed of 50 km/h with a tolerance of ± 1 km/h between
AA' and BB'. During the constant speed test the acceleration control shall be positioned
to maintain a constant speed between AA' and BB' as specified. If the gear is locked for
the acceleration test, the same gear shall be locked for the constant speed test.
The constant speed test is not required for vehicles with a PMR < 25.
3.1.2.2. Vehicles of Categories M > 3 500 kg, M , N , N
The path of the centreline of the vehicle shall follow Line CC' as closely as possible
throughout the entire test, from the approach to Line AA' until the rear of the vehicle
passes Line BB'. The test shall be conducted without a trailer or semi-trailer. If a trailer
is not readily separable from the towing vehicle the trailer shall be ignored when
considering the crossing of Line BB'. If the vehicle incorporates equipment such as a
concrete mixer, a compressor, etc, this equipment shall not be in operation during the
test. The test mass of the vehicle shall be according to the table of Paragraph 2.2.1.
Target conditions of Category M > 3 500 kg, N :

3.1.2.2.2. Acceleration Test
When the reference point of the vehicle reaches the Line AA' the accelerator control shall
be fully depressed (without operating the automatic downshift to a lower range than
normally used in urban driving) and held fully depressed until the rear of the vehicle
passes BB', but the reference point shall be at least 5 m behind BB'. The accelerator
control shall then be released.
In the case of articulated vehicles consisting of two non-separable units regarded as a
single vehicle, the semi-trailer shall be disregarded in determining when Line BB' is
crossed.
3.1.3. Interpretation of Results
The maximum A-weighted sound pressure level indicated during each passage of the
vehicle between the two Lines AA' and BB' shall be noted. If a noise peak obviously out
of character with the general sound pressure level is observed, the measurement shall
be discarded. At least four measurements for each test condition shall be made on each
side of the vehicle and for each gear ratio. Left and right side may be measured
simultaneously or sequentially. The first four valid consecutive measurement results,
within 2 dB(A), allowing for the deletion of non valid results (see Paragraph 2.1.), shall be
used for the calculation of the final result for the given side of the vehicle. The results of
each side shall be averaged separately. The intermediate result is the higher value of
the two averages mathematically rounded to the first decimal place.
The speed measurements at AA', BB', and PP' shall be noted and used in calculations to
the first significant digit after the decimal place.
The calculated acceleration a
shall be noted to the second digit after the decimal
place.
3.1.3.1. Vehicles of Categories M , N and M ≤ 3 500 kg
The calculated values for the acceleration test and the constant speed test are given by:
L = L + k × (L – L )
L = L + k × (L – L )
Where k = (a a )/(a – a )
In the case of a single gear ratio test the values are the test result of each test.
The final result is calculated by combining L and L . The equation is:
L = L – k × (L – L )
The weighting factor k gives the part power factor for urban driving. In cases other than
a single gear test k is calculated by:
k = 1 – (a / a )

3.2.5.2. Positioning and Preparation of the Vehicle
The vehicle shall be located in the centre part of the test area with the gear selector in
the neutral position and the clutch engaged. If the design of the vehicle does not allow
this, the vehicle shall be tested in conformity with the manufacturer's prescriptions for
stationary engine testing. Before each series of measurements, the engine must be
brought to its normal operating condition, as specified by the manufacturer.
If the vehicle is fitted with fan(s) having an automatic actuating mechanism, this system
shall not be interfered with during the sound level measurements.
The engine hood or compartment cover, if so fitted, shall be closed.
3.2.5.3. Measuring of Noise in Proximity to the Exhaust (see Appendix of Annex 3, Figure 1)
3.2.5.3.1. Positions of the Microphone
3.2.5.3.1.1. The microphone shall be located at a distance of 0.5 m ± 0.01 m from the reference point
of the exhaust pipe defined in Figure 1, and at an angle of 45° (± 5°) to the flow axis of
the pipe termination. The microphone shall be at the height of the reference point, but
not less than 0.2 m from the ground surface. The reference axis of the microphone shall
lie in a plane parallel to the ground surface and shall be directed toward the reference
point on the exhaust outlet. If two microphone positions are possible, the location
farthest laterally from the vehicle longitudinal centreline shall be used. If the flow axis of
the exhaust outlet pipe is at 90° to the vehicle longitudinal centreline, the microphone
shall be located at the point, which is farthest from the engine.
3.2.5.3.1.2. For vehicles having an exhaust provided with outlets spaced more than 0.3 m apart,
measurements shall be made for each outlet. The highest level shall be recorded.
3.2.5.3.1.3. In the case of an exhaust provided with two or more outlets spaced less than 0.3 m apart
and which are connected to the same silencer, only one measurement is made; the
microphone position is related to the outlet nearest to one extreme edge of the vehicle
or, when such outlet does not exist, to the outlet which is the highest above the ground.
3.2.5.3.1.4. For vehicles with a vertical exhaust (e.g. commercial vehicles) the microphone shall be
placed at the height of the exhaust outlet. Its axis shall be vertical and oriented upwards.
It shall be placed at a distance of 0.5 m ± 0.01 m from the exhaust pipe reference point,
but never less than 0.2 m from the side of the vehicle nearest to the exhaust.
3.2.5.3.1.5.1. For exhaust outlets located under the vehicle body, the microphone shall be located a
minimum of 0.2 m from the nearest part of the vehicle, at a point closest to, but never
less than 0.5 m from the exhaust pipe reference point, and at a height of 0.2 m above the
ground, and not in line with the exhaust flow. The angularity requirement in
Paragraph 3.2.5.3.1.2. may not be met in some cases.

Noise.