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IS0
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
IS0 RECOMMENDATION
R 362
MEASUREMENT OF NOISE EMITTED BY VEHICLES
1st EDITION
February 1964
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized &herefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Rinted in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 362, Measurement of Noise Emitted by Vehicles, was
drawn up by Technical Committee ISO/TC 43, Acoustics, the Secretariat of which is held
by the British Standards Institution (B.S.I.).
Work on this question by the Technical Committee began in 1958 and led, in 1960, to
the adoption of a Draft IS0 Recommendation.
This first Draft IS0 Recommendation (No. 419) was circulated to all the IS0 Member
Bodies for enquiry, in November 1960. Taking into account the observations put forward
by the Technical Committee ISO/TC 22, Automobiles, regarding mechanical specifications,
Technical Committee ISO/TC 43 presented a Second Draft IS0 Recommendation, which
was circulated to all the IS0 Member Bodies in May 1962, and which was approved,
subject to a few modifications of an editorial nature, by the following Member Bodies:
Australia France Poland
Austria Germany Portugal
Belgium Greece Spain
Brazil Hungary Sweden
Canada India Switzerland
Chile Ir e 1 and United Kingdom
Czechoslovakia Israel U.S.A.
Denmark Netherlands U.S.S.R.
Finland New Zealand Yugoslavia
One Member Body opposed the approval of the Draft : Japan.
The second Draft IS0 Recommendation was then submitted by correspondence to the
IS0 Council, which decided, in February 1964, to accept it as an IS0 RECOMMEN-
DATION.
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iSO/ R 362 - 1964 (E)
IS0 Recommendation R 362 February 1964
MEASUREMENT OF NOISE EMITTED BY VEHICLES
1. SCOPE
This IS0 Recommendation describes methods of determining the noise emitted by motor vehicles,
these being intended to meet the requirements of simplicity as far as is consistent with repro-
ducibility of results and realism in the operating conditions of the vehicle.
2. GENERAL. REQUIREMENTS
2.1 Test conditions
This IS0 Recommendation is based primarily on a test with vehicles in motion, the IS0
reference test. It is generally recognized to be of primary importance that the measurements
should relate to normal town driving conditions, thus including transmission noise etc.
Measurements should also relate to vehicle conditions which give the highest noise level
consistent with normal driving and which lead to reproducible noise emission. Therefore,
an acceleration test at full throttle from a stated running condition is specified.
Recognizing, however, that different practices already exist, specifications of two other
methods used are also given in the Appendix. These relate to:
(a) a test with stationary vehicles (see Appendix Al) and
(b) a test with vehicles in motion, under vehicle conditions which (in the case of certain
vehicles) are different from those in the IS0 reference test (see Appendix A2).
When either of these tests is used, the relation between the results and those obtained by
the IS0 reference test should be established for typical examples of the model concerned.
2.2 Test site
The test methods prescribed call for an acoustical environment which can only be obtained
in an extensive open space. Such conditions can usually be provided
for type-approval measurements of vehicles,
.
for measurements at the manufacturing stage, and
for measurements at official testing stations.
It is desirable that spot checking of vehicles on the road should be made in a similar
acoustical environment. If measurements have to be carried out on the road in an acoustical
environment which does not fulfil the requirements stated in this IS0 Recommendation,
it should be recognized that the results obtained may deviate appreciably from the results
obtained using the specified conditions.
2.3 Interpretation of results
The results obtained by the methods specified give an objective measure of the noise emitted
under the prescribed conditions of test. Owing, however, to the fact that the subjective
appraisal of the annoyance or noisiness of different classes of motor vehicles is not simply
related to the indications of a sound level meter, it is recognized that the correct interpre-
tation of results of the measurements in this IS0 Recommendation may require different
limits to be set for the corresponding annoyance of different classes of vehicles.
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iSO/ R 362 - 1964 (E)
3. MEASUREMENT EQUIPMENT
A high quality sound level meter should be used. The weighting network and meter time constant
employed should be curve " A " and " fast response " respectively, as specified in Recommen-
dation No. 123 of the International Electrotechnical Commission for Sound Level Meters. A
detailed technical description of the instrument used should be supplied.
NOTES
1. The sound level measured using sound level meters having the microphone close to the instrument
case may depend on the orientation of the instrument with respect to the sound source, as well as on
the position of the observer making the measurement. The instructions given by the manufacturer
concerning the orientation of the sound level meter with respect to the sound source and the observer
should therefore be carefully followed.
2. If a wind shield is used for the microphone, it should be remembered that this may have an influence
on the sensitivity of the sound level meter.
3. To ensure accurate measurements, it is recommended that before each series of measurements the
anîplification of the sound level meter be checked, using a standard noise source and adjusting as
necessary.
4. it is recommended that the sound level meter and the standard noise source be calibrated periodically
at a laboratory equipped with the necessary facilities for free-field calibration.
Any peak which is obviously out of character with the general sound level being read should be
ignored.
4. ACOUSTICAL ENVIRONMENT
The test site should be such that hemispherical divergence exists to within f 1 dB.
NoTE.-A suitable test site, which could be considered ideal for the purpose of the measurements, would
consist of an open space of some 50 m radius, of which the central 20 m, for example, would consist of
concrete, asphalt or similar hard material.
In practice, departure from the so-called " ideal " conditions arises from four main causes:
(a) sound absorption by the surface of the ground;
(b) reflections from objects, such as buildings, and trees, or from persons;
(c) ground which is not level or of uniform slope over a sufficient area;
(d) wind.
It is impracticable to specify in detail the effect produced by each of these influences. It is con-
sidered important, however, that the surface of the ground within the measurement area be free
from powdery snow, long grass, loose soil or ashes.
To minimise the effect of reflections, it is further recommended that the sum of the angles sub-
tended at the position of the test vehicle by surrounding buildings within 50 m radius should not
exceed 90" and that there be no substantial obstructions within a radius of 25 m from the vehicle.
Acoustical focussing effects and sites between parallel walls should be avoided.
Wherever possible, the level of ambient noise (including wind noise and-for stationary tests-
on the meter is at least
roller stand and tyre noise) should be such that the reading produced
10 dB below that produced by the test vehicle. In other cases, the prevailing noise level should be
stated in terms of the reading of the meter.
NOTE.-Care should be taken that gusts of wind do not distort the results of the measurements.
The presence of bystanders may have an appreciable influence on the meter reading, if such
persons are in the vicinity of the vehicle or the microphone. No person other than the observer
reading the meter should therefore remain in the neighbourhood of the vehicle or the microphone.
NoTE.-Suitabie conditions exist, if bystanders are at a distance from the vehicle which is at least twice
th
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