ISO 16254:2024
(Main)Acoustics — Measurement of sound emitted by road vehicles of category M and N at standstill and low speed operation — Engineering method
Acoustics — Measurement of sound emitted by road vehicles of category M and N at standstill and low speed operation — Engineering method
This document is derived from ISO 362-1[2] and specifies an engineering method for measuring the sound emitted by M and N category road vehicles at standstill and low speed operating conditions. The specifications reproduce the level of sound which is generated by the principal vehicle sound sources consistent with stationary and low speed vehicle operating conditions relevant for pedestrian safety. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. The test method requires an acoustic environment which is only obtained in an extensive open space. Such conditions usually exist during the following: — measurements of vehicles for regulatory certification; — measurements at the manufacturing stage; — measurements at official testing stations. The results obtained by this method give an objective measure of the sound emitted under the specified conditions of test. It is necessary to consider the fact that the subjective appraisal of the annoyance, perceptibility, and/or detectability of different motor vehicles or classes of motor vehicles due to their sound emission are not simply related to the indications of a sound measurement system. As annoyance, perceptibility and/or detectability are strongly related to personal human perception, physiological human condition, culture, and environmental conditions, there are large variations and therefore these terms are not useful as parameters to describe a specific vehicle condition. Spot checks of vehicles chosen at random rarely occur in an ideal acoustic environment. If measurements are carried out on the road in an acoustic environment which does not fulfil the requirements stated in this document, the results obtained might deviate appreciably from the results obtained using the specified conditions. In addition, this document provides an engineering method to measure the performance of external sound generation systems intended for the purpose of providing acoustic information to pedestrians on a vehicle’s operating condition. This information is reported as objective criteria related to the external sound generation system’s sound pressure level, frequency content, and changes in sound pressure level and frequency content as a function of vehicle speed. This document adds a metric related to the human perception of tonal loudness, the psychoacoustic tonality. The psychoacoustic tonality can be used to estimate audible frequency shifts of the sounds by identifying the most audible component in each auditory frequency band (critical band), as well as to determine if the band(s) so identified meet audibility criteria. Annex A and Annex C contains background information relevant in the development of this document.
Acoustique — Mesurage du bruit émis par les véhicules routiers de catégories M et N à l'arrêt et en fonctionnement à basse vitesse — Méthode d'expertise
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Standards Content (Sample)
International
Standard
ISO 16254
Second edition
Acoustics — Measurement of sound
2024-12
emitted by road vehicles of category
M and N at standstill and low speed
operation — Engineering method
Acoustique — Mesurage du bruit émis par les véhicules routiers
de catégories M et N à l'arrêt et en fonctionnement à basse vitesse
— Méthode d'expertise
Reference number
© ISO 2024
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Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms. 3
5 Instrumentation . 6
5.1 Instruments for acoustic measurement .6
5.1.1 General .6
5.1.2 Daily verification and adjustment.7
5.1.3 Conformity with requirements .7
5.2 Instrumentation for speed measurements .7
5.3 Meteorological instrumentation .8
6 Acoustic environment, meteorological conditions, and background noise . 8
6.1 Test site .8
6.1.1 General .8
6.1.2 Outdoor testing .8
6.1.3 Indoor hemi anechoic or anechoic testing .9
6.1.4 Indoor external sound generation system testing .11
6.2 Meteorological conditions .11
6.2.1 General .11
6.2.2 Outdoor measurements .11
6.2.3 Indoor measurements .11
6.3 Background noise.11
6.3.1 Measurement criteria for A-weighted sound pressure level .11
6.3.2 Background noise requirements when analysing in one-third octave bands . 12
6.3.3 Measurement background noise when testing a component . 13
7 Test procedures .13
7.1 Full vehicle testing . 13
7.1.1 Microphone positions . . . 13
7.1.2 Conditions of the vehicle . 13
7.1.3 Test mass of vehicle.14
7.1.4 Tyre selection and condition .14
7.1.5 Operating conditions .14
7.1.6 Measurement readings and reported values .16
7.1.7 Data compilation .18
7.1.8 Reported standstill results .19
7.1.9 Reported slow speed cruise result at 10 km/h . 20
7.2 Measurement of sound to determine frequency shift . 20
7.2.1 General . 20
7.2.2 Instrumentation. 20
7.2.3 Signal processing requirements . 20
7.2.4 Test facilities . 20
7.2.5 Frequency shift measurement test procedure .21
7.3 Measurement uncertainty . . 23
8 Test report .24
Annex A (informative) Information on development of ISO 16254 .27
Annex B (informative) Development of frequency shift information .29
Annex C (informative) Relevance of objective acoustic data to pedestrian safety .31
iii
Annex D (informative) Measurement uncertainty – Framework for analysis according to ISO/
IEC Guide 98-3 (GUM) .33
Annex E (informative) Testing requirements for reduced uncertainty . 41
Annex F (informative) Frequency identification of tones using the fast Fourier transformation .42
Annex G (informative) Flowchart of the procedure for measurement and reporting of
background noise.44
Annex H (informative) Flowchart for the procedure to measure and report A-weighted sound
pressure levels .45
Annex I (informative) Flowchart for the procedure to report A-weighted one-third octave band
sound pressure levels . 47
Annex J (informative) Tonality .48
Bibliography .54
iv
Foreword
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This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise, in
collaboration with ISO/TC 22, Road vehicles.
This second edition cancels and replaces the first edition (ISO 16254:2016), which has been tech
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