Microsoft Word C042211e doc Reference number ISO 362 2 2009(E) © ISO 2009 INTERNATIONAL STANDARD ISO 362 2 First edition 2009 07 15 Measurement of noise emitted by accelerating road vehicles — Enginee[.]
General
Vehicle acceleration is calculated using different speeds measured on the test track The formulas in section 5.2 are applied to determine acceleration values at various points, such as a_wot(i), a_wot(i+1), and during the WOT test The vehicle's speed at reference points AA′ (v AA′) or PP′ (v PP′) is recorded when the vehicle passes these points, while the speed at BB′ (v BB′) is measured when the rear of the vehicle passes BB′ The chosen method for calculating acceleration must be clearly documented in the test report to ensure transparency and consistency.
With the front of the vehicle as the reference point, l ref = l veh is the length of vehicle
The dimensions of the test track are used in the calculation of the acceleration These dimensions are defined as follows: l 20 = 20 m, l 10 = 10 m
Given the wide range of automotive technologies, it is essential to employ different methods of calculation to ensure accuracy Modern systems like continuously variable transmissions (CVT) and traditional automatics without electronic controls require tailored approaches for precise acceleration determination The calculation methods provided are designed to address the unique characteristics of both new and older transmission technologies, ensuring comprehensive and reliable results.
Calculation of acceleration
5.2.1 Calculation procedure for vehicles with manual transmission, automatic transmission, adaptive transmission and continuously variable transmission (CVT) tested with locked gear ratios
The value of a wot test used in the determination of gear selection shall be the average of the four a wot test, j values during each valid measurement run
Calculate a wot test, j using Equation (2):
The article discusses key parameters involved in testing and measurement, including the WOT test, where 'j' represents the acceleration in meters per second squared It highlights the importance of speed measurements, with 'v BB′' and 'v AA′' expressed in kilometers per hour, in assessing vehicle or object performance Additionally, length measurements such as 'l 20' and 'l ref' are provided in meters, emphasizing precise dimensional analysis crucial for accurate testing and evaluation.
Pre-acceleration may be used
5.2.2 Calculation procedure for vehicles with automatic transmission, adaptive transmission and
CVT tested with non-locked gear ratios
The value of a wot test used in the determination of gear selection shall be the average of the four a wot test, j values during each valid measurement run
If devices or measures described in 8.3.1.3.3 are used to control transmission operation for the purpose of achieving test requirements, calculate a wot test, j using Equation (2)
Pre-acceleration may be used
If no devices or measures described in 8.3.1.3.3 are used, calculate a wot test, j using Equation (3):
The article defines key parameters used in WOT testing, including the acceleration value 'j,' measured in meters per second squared, and vehicle speeds 'v_PP′' and 'v_BB′,' expressed in kilometers per hour It also references length measurements 'l_10' and 'l_ref,' provided in meters These parameters are essential for accurate assessment and analysis during vehicle testing procedures.
Pre-acceleration shall not be used
Recording vehicle speeds at points AA′, PP′, and BB′ is essential for enhancing the accuracy of data collection This information will support future revisions of ISO 362, ensuring better standardization and safety in vehicle testing protocols Incorporating speed recordings at these key locations improves the quality and reliability of vehicle performance assessments, making it a valuable practice for industry stakeholders.
Calculation of the target acceleration
Calculate a urban using Equation (4) or (5): a urban = 1,37 lg(PMR) − 1,08 for 25 < PMR u 50 (4) a urban = 1,28 lg(PMR) − 1,19 for PMR > 50 (5) where a urban is the numerical value of acceleration, expressed in metres per second squared;
PMR is the dimensionless value of the power-to-mass index
Calculation of the reference acceleration
Calculate the reference acceleration (a_wot_ref) using the equations: for PMR values between 25 and 50, a_wot_ref = 2.47 * lg(PMR) - 2.52; for PMR values greater than 50, a_wot_ref = 3.33 * lg(PMR) - 4.16 The a_wot_ref represents the numerical value of the reference acceleration measured in meters per second squared, while PMR is a dimensionless index indicating the power-to-mass ratio These formulas help determine the appropriate reference acceleration based on the PMR value for accurate engineering assessments.
NOTE Calculations of a wot ref and a urban for a specific vehicle are based on statistical analyses of in-use vehicle data
As such, this is not strictly a calculation of acceleration based on the independent non-dimensional variable PMR, since this is used as a function to identify the appropriate target acceleration.
Partial power factor k P
Partial power factor k P is: k P = 1 − (a urban / a wot test ) (8)
In cases other than a single gear test, a wot ref shall be used instead of a wot test as defined in 8.4.3.1
Instruments for acoustical measurement
To accurately measure sound pressure levels, a Class 1 sound level meter or an equivalent measurement system must be used, complying with IEC 61672-1 standards The instrument should include the recommended windscreen, if applicable, to ensure precise and reliable measurements.
The entire measurement system shall be checked by means of a sound calibrator that fulfils the requirements of Class 1 sound calibrators according to IEC 60942
Measurements shall be carried out using the time weighting “F” of the acoustic measuring instrument and the
The "A" frequency weighting curve, as defined in IEC 61672-1, is essential for accurately measuring sound pressure levels When utilizing a system that periodically monitors A-weighted sound levels, it is important to take each reading at intervals no longer than 30 milliseconds to ensure precise and reliable data collection.
The instruments shall be maintained and calibrated in accordance with the instructions of the instrument manufacturer
Before and after each measurement session, the entire acoustic measurement system must be verified using a sound calibrator as outlined in section 6.1.1 The calibration check should show a difference of no more than 0.5 dB; if this limit is exceeded, all subsequent measurement results must be discarded to ensure accuracy.
Annual verification of the sound calibrator’s compliance with IEC 60942 is essential to maintain calibration accuracy Additionally, the instrumentation system must be checked for compliance with IEC 61672-1 at least every two years to ensure measurement reliability All compliance testing should be carried out by an authorized laboratory qualified to perform calibrations traceable to recognized standards.
Instrumentation for engine and vehicle speed measurements
The engine speed shall be measured with an instrument meeting specification limits of at least ± 2 % at the engine speeds required for the measurements being performed
The road speed of the vehicle shall be measured with instruments meeting specification limits of at least ± 0,5 km/h when using continuous measuring devices
If testing uses independent measurements of speed, this instrumentation shall meet specification limits of at least ± 0,2 km/h
Independent speed measurements involve using two or more separate devices to determine the values of v AA′, v BB′, and v PP′ In contrast, a continuous measuring device can obtain all necessary speed information with a single measurement system Accurate speed assessment is essential for precise data analysis and system performance evaluation Using multiple devices ensures measurement redundancy and reliability, while continuous devices offer streamlined data collection for efficient operations.
Meteorological instrumentation
The meteorological instrumentation used to monitor the environmental conditions during the test shall meet the following specifications:
⎯ ± 1 °C or less for a temperature measuring device;
⎯ ± 1,0 m/s for a wind speed measuring device;
⎯ ± 5 hPa for a barometric pressure measuring device;
⎯ ± 5 % for a relative humidity measuring device
7 Acoustical environment, meteorological conditions and background noise
Test site
The test site shall be substantially level The test track construction and surface shall meet the requirements of ISO 10844 The test site dimensions are shown in Figure 1
NOTE 1 The symbols in Figure 1 are directly copied from ISO 10844 and are not necessarily consistent with the symbols in this part of ISO 362
Ensure that within 50 meters of the track center, the area is clear of large reflective objects like fences, rocks, bridges, or buildings The test track and surrounding surface must be dry and free from absorbent materials such as powdery snow or loose debris to guarantee optimal testing conditions.
Ensure there are no obstacles around the microphone that could affect the acoustical field, and prevent any persons from standing between the noise source and the microphone The meter observer must be positioned in a way that does not influence the accuracy of the noise measurement.
NOTE 2 Buildings outside the 50 m radius can have significant influence if their reflection focuses on the test track
Key minimum area covered with test road surface, i.e test area microphone positions (height 1,2 m)
CC′ line of vehicle travel through test zone
PP′ line perpendicular to vehicle travel between microphone locations
R50 radius of 50 m around the centre of the track
NOTE The shaded area (“test area”) is the minimum area to be covered with a surface complying with ISO 10844
Meteorological conditions
Meteorological instrumentation must provide accurate data reflective of the test site conditions It should be strategically positioned adjacent to the test area at a height that matches the measuring microphone's elevation, ensuring precise and relevant environmental measurements.
Measurement of ambient noise should be conducted when the air temperature is between 5 °C and 40 °C to ensure accuracy Noise tests must be avoided if wind speeds at microphone height exceed 5 m/s, including gusts, during the measurement period to maintain reliable results.
A value representative of temperature, wind speed and direction, relative humidity and barometric pressure shall be recorded during the noise measurement interval
NOTE Refer to Annex B for the effects of temperature and other factors
Background noise
Any sound peak which appears to be unrelated to the characteristics of the general level of noise of the vehicle shall be ignored when taking the readings
Background noise measurements should be taken for 10 seconds immediately prior to and following each vehicle test, using the same microphones and locations employed during the testing process The key metric to report is the maximum A-weighted sound pressure level observed during these measurements, ensuring consistency and accuracy in noise level assessment.
Background noise, including wind noise, must be at least 10 dB below the A-weighted sound pressure level produced by the vehicle during testing If the background sound pressure level is within 10 to 15 dB of the measured vehicle noise, an appropriate correction, as detailed in Table 2, must be subtracted from the sound level meter readings to ensure accurate test results This correction process is essential for obtaining precise vehicle sound measurements and maintaining compliance with noise regulation standards.
Table 2 — Correction applied to an individual measured test value
Background sound pressure level difference to measured sound pressure level, in dB
10 11 12 13 14 greater than or equal to 15
Microphone positions
The distance from the microphone positions on the microphone line PP′ to the perpendicular reference line CC′ (see Figure 1) on the test track shall be 7,5 m ± 0,05 m
The microphone should be positioned 1.2 meters ± 0.02 meters above ground level to ensure accurate sound measurement For free-field conditions, the reference direction must be horizontal and perpendicular to the vehicle's path, as specified by IEC 61672-1 standards Proper microphone placement according to these guidelines guarantees reliable and consistent audio assessments in vehicle noise testing.
Conditions of the vehicle
The vehicle shall be supplied as specified by the vehicle manufacturer
Before the measurements are started, the vehicle shall be brought to its normal operating conditions
The variation of results between runs may be reduced if there is an approximate 60 s wait, at idle in neutral, between runs
8.2.2 Test mass of the vehicle
Measurements shall be made on vehicles at the test mass m t , in kilograms, specified as: m t = m ref = m kerb + m d = m kerb + 75 kg ± 5 kg
NOTE 75 kg ± 5 kg equates to mass of the driver, m d
The tyres shall be appropriate for the vehicle and shall be inflated to the pressure recommended by the tyre manufacturer for the test mass of the vehicle
For certification purposes, specific regulatory requirements for tyres are essential to ensure compliance The vehicle manufacturer must select tyres that match one of the approved sizes and types designated for the vehicle, with the tyres being commercially available on the market at the time of the vehicle’s release Additionally, the tyres used in tests must have a minimum tread depth of at least 80% of the full tread depth, ensuring safety and performance standards are met.
NOTE The tread depth and pattern can have a significant influence on the test result.
Operating conditions
8.3.1 Vehicles of category L3 with PMR > 25
The vehicle’s centerline should follow line CC′ as closely as possible throughout the test, from approaching line AA′ until the rear passes line BB′ (see Figure 1) Trailers that cannot be easily separated from the towing vehicle should be disregarded when assessing crossing line BB′ For vehicles with more than two-wheel drive, testing should be conducted in the drive mode intended for normal road use, and if equipped with an auxiliary manual transmission or multi-gear axle, the urban driving gear setting should be used Gear ratios used for slow movements, parking, or braking are to be excluded from the test results.
The test speed, v test , shall be:
The test speed is considered reached when the reference point (3.5) aligns with line PP′ If the exit speed (v BB′) exceeds 75% of the maximum speed (v max), the test speed should be decreased incrementally by 10% These guidelines ensure accurate and consistent testing protocols for vehicle performance assessments.
It is the responsibility of the manufacturer to determine the correct manner of testing to achieve the required accelerations
Annex C gives gear selection criteria and test run criteria in a flowchart form as an aid to test operation
8.3.1.3.2 Manual transmission, automatic transmissions, adaptive transmissions or transmissions with continuously variable gear ratios (CVTs) tested with locked gear ratios
The selection of gear ratios for testing is based on the vehicle's specific acceleration potential at wide-open throttle (WOT), as outlined in section 5.2 This ensures the actual acceleration (a_wot_i) aligns with the reference acceleration (a_wot_ref) required for the WOT acceleration test Proper gear ratio choice is determined in relation to equations (6) or (7) in section 5.4, facilitating accurate and standardized testing conditions.
The following conditions for selection of gear ratios are possible
When selecting gear ratios for testing based on acceleration tolerance, if two gear ratios fall within ±10% of the reference acceleration, both should be used with a gear ratio weighting factor calculated accordingly If only one gear ratio meets the ±10% tolerance, that ratio should be used for the test In cases where no gear ratios meet the required acceleration, select one with higher acceleration (gear ratio i) and another with lower acceleration (gear ratio i + 1), and use both for testing The gear ratio weighting factor is determined by the formula: k = [a_wot_ref – a_wot(i + 1)] / [a_wot i – a_wot(i + 1)].
For vehicles with a single-gear ratio transmission, the wide-open-throttle (WOT) test is conducted using this gear setting The acceleration achieved during the WOT test is utilized to calculate the partial power factor, k_P, instead of relying on a WOT reference.
If rated engine speed is exceeded in a gear ratio before the vehicle passes BB′, the next higher gear shall be used
8.3.1.3.3 Automatic transmission, adaptive transmissions and transmissions with variable gear ratios tested with non-locked gear ratios
The gear selector position for full automatic operation shall be used
The acceleration a wot test shall be calculated by either Equation (2) or Equation (3) as specified in 5.2
During testing, it is essential to include a gear change to a lower gear ratio to achieve higher acceleration, while shifting to a higher gear range with lower acceleration is not permitted Gear shifts to ratios that are not typically used in the specified urban traffic conditions should be avoided to ensure accurate and compliant testing procedures.
Electronic and mechanical devices, including alternative gear selector positions, are permitted to prevent downshifting to gear ratios that are not typically used under specific test conditions in urban traffic This ensures optimal vehicle performance and compliance with testing standards, making the use of such devices essential for urban driving scenarios.
The achieved acceleration, a wot test , shall be greater or equal to a urban
The achieved acceleration, a wot test , is then used for the calculation of the partial power factor, k P (see 3.9) instead of a wot ref
The acceleration test shall be carried out in all gear ratios specified for the vehicle according to 8.3.1.3 with the test speed specified in 8.3.1.2
The acceleration control unit is fully engaged when the front of the vehicle reaches point AA′ and remains engaged until the rear reaches point BB′, after which it should be released If there is a delay in acceleration beyond point AA′, pre-acceleration can be utilized to ensure smooth vehicle operation The precise starting point of acceleration must be reported for accurate monitoring and compliance with operational protocols.
The calculated acceleration, a wot test , shall be mathematically rounded to the nearest second decimal place
For vehicles with transmissions specified in section 8.3.1.3.2, the constant speed test must be conducted using the same gears used during the acceleration test to ensure consistency Conversely, for vehicles with transmissions specified in section 8.3.1.3.3, the gear selector should be set to full automatic operation during testing If the gear is locked for the acceleration test, the same gear lock should be maintained during the constant speed test for accurate results.
During the constant speed test, the acceleration control unit shall be positioned to maintain a constant speed between AA′ and BB′ as specified in 8.3.1.2
8.3.2 Vehicles of category L3 with PMR u 25
The sole operating condition involves conducting a wide-open-throttle acceleration test under specified general conditions outlined in 8.3.1.1 The initial test speed should align with the parameters set in 8.3.1.2 If the exit speed v BB′ exceeds 75% of the maximum speed v max or if the engine speed surpasses the rated engine speed S at BB′, the test speed must be decreased in 10% decrements of the initial test speed v test The chosen gear ratio should be the lowest that does not cause the engine to exceed the rated speed S during testing Final test conditions are established at the lowest possible gear ratio and highest test speed that stay within the 75% v max limit and do not exceed the rated engine speed S at BB′.
The only operating condition is a wide-open-throttle acceleration test
The vehicle shall approach AA′ at a constant speed corresponding to the lower of the following speeds:
⎯ the vehicle speed corresponding to an engine speed equal to 75 % of S
If there is a downshift to first gear during the test, the vehicle speed can be increased up to a maximum of
60 km/h to avoid the downshift
The test must be conducted with the manual selector set to the highest position Any automatic downshift to the first gear should be disregarded during the test If an automatic downshift occurs to the second or third highest gear ratios, the selector should be adjusted to the highest position to prevent automatic downshifting, ensuring accurate test results.
If an electronic transmission cannot be tested, a programme shall be established and used that prevents a downshift to a gear not normal for urban driving
The vehicle shall approach AA′ at a constant speed corresponding to the lower of the following speeds:
⎯ the vehicle speed corresponding to an engine speed equal to 75 % of S
Vehicles equipped with gearboxes of four or fewer gears must be tested in second gear If the engine speed at point BB′ surpasses the limit S, the test should then be conducted in the next higher gear ratio This procedure ensures accurate assessment of vehicle performance and compliance with emissions standards.
Vehicles fitted with five or more gears shall be tested in the following gears
⎯ Vehicles fitted with an engine having a cylinder capacity not exceeding 175 cm 3 shall be tested only in third gear
⎯ Vehicles fitted with an engine having a cylinder capacity exceeding 175 cm 3 shall be tested in second gear and in third gear
⎯ If the engine speed at the line BB′ exceeds S, test only in third gear
Vehicles without a manual selector shall approach AA′ at the various uniform speeds of 30 km/h, 40 km/h and
50 km/h, or at 75 % of v max if this value is lower.
Measurement readings and reported values
At least four measurements for all test conditions shall be made on each side of the vehicle and for each gear ratio
During each vehicle passage between points AA′ and BB′ (refer to Figure 1), the maximum A-weighted sound pressure level should be recorded and rounded to the nearest first decimal place (e.g., XX.X) If an anomalous sound peak significantly deviates from the overall sound pressure level, that measurement must be discarded to ensure accurate noise assessment.
For each test condition, the first four valid consecutive measurement results, within a tolerance of 2.0 dB, should be used to calculate the intermediate or final measurement Non-valid results may be omitted to ensure accuracy This process guarantees reliable and consistent measurement outcomes.
The speed measurements at AA′ (v AA′ ), BB′ (v BB′ ) and PP′ (v PP′ ) shall be mathematically rounded to the nearest first decimal place
When evaluating test conditions, the results for each side of the vehicle should be averaged separately The final intermediate result is determined by selecting the higher of the two averages This value should be rounded to the first decimal place to ensure accuracy and consistency in reporting.
All calculations to determine L urban should be performed separately for the left and right sides of the vehicle The final test result should be reported as the higher value between the two sides.
8.4.3 Vehicles of category L3 with PMR > 25
The average acceleration during the WOT (Wide Open Throttle) test is calculated by taking the mean of four test runs, expressed as: a WOT test = 1/4 (a WOT test 1 + a WOT test 2 + a WOT test 3 + a WOT test 4) This formula ensures an accurate representation of the vehicle's acceleration performance across multiple test scenarios.
8.4.3.2 Reported value and final results
Calculate the reported value L wot rep for the wide-open-throttle test using the equation:
L wot rep = L wot (i + 1) + k [L wot i − L wot (i + 1)] (11)
`,,```,,,,````-`-`,,`,,`,`,,` - where k is the gear ratio weighting factor
Calculate the reported value L crs rep for the constant speed test using the equation:
L crs rep = L crs (i + 1) + k [L crs i − L crs (i + 1)] (12)
In the case of a single gear ratio test, the reported values are directly derived from the test result itself
The partial power factor, kP, is calculated using specific equations depending on testing conditions When conducting tests involving multiple gears, kP is determined by subtracting the ratio of a urban to a reference value from one: kP = 1 − (a urban / a wot ref) If only a single gear is tested, the calculation adjusts accordingly, with kP = 1 − (a urban / a wot test) In cases where the a wot test value is less than the a urban value, the partial power factor is set to zero, kP = 0 These equations are essential for accurately assessing gear performance under different testing scenarios.
The final result is calculated by combining Equation (11) for L wot rep and Equation (12) for L crs rep :
L urban = L wot rep − k P (L wot rep − L crs rep ) (16)
8.4.4 Vehicles of category L3 with PMR u 25
The intermediate result in 8.4.2 shall be the final result
The final result depends on the testing method used: for vehicles tested in a single gear, it is the intermediate result as specified in section 8.4.2; for vehicles tested in two gears, it is the arithmetic average of the intermediate results for each gear; and for vehicles tested at multiple speeds, it is the highest intermediate result among all tested speeds.
Measurement uncertainty
The measurement procedure outlined in section 8.4 is influenced by various parameters, such as surface texture variations per ISO 10844, environmental conditions, and measurement system uncertainties, leading to variability in the observed levels for the same subject These sources of perturbation are not fully understood and can sometimes unpredictably impact the final results To assess the uncertainty of measurements conducted according to ISO 362, the recommended evaluation procedure should be followed.
According to ISO/IEC Guide 98-3 and ISO 5725 standards, uncertainty estimates were derived in the absence of extensive inter- and intra-laboratory data by following ISO/IEC Guide 98-3 procedures These uncertainties were based on existing statistical data, analysis of tolerances in ISO 362, and engineering judgment They are categorized into three groups: (a) variations within the same test laboratory and minor ambient changes during a single test series (run-to-run); (b) variations within the same laboratory over a year, accounting for daily ambient and equipment differences; and (c) differences between test laboratories, considering variations in ambient conditions, equipment, staff, and road surface conditions (site-to-site).
When reporting measurement results, it is essential to provide the expanded uncertainty along with the corresponding coverage probability, as specified in ISO/IEC Guide 98-3 Details on how to determine the expanded uncertainty are explained in Annex B, ensuring transparency and compliance with international standards.
NOTE Annex B gives a framework for analysis in accordance with ISO/IEC Guide 98-3, which can be used to conduct future research on measurement uncertainty for this part of ISO 362
The data given in Table 3 express the variability of results for vehicles of category L for a coverage probability of 80 % These data do not cover product variation
Table 3 — Variability of measurement results for a coverage probability of 80 %
Until more specific knowledge is available, the data for site-to-site variability might be used in test reports to state the expanded measurement uncertainty for a coverage probability of 80 %
The test report must include comprehensive details such as references to ISO 362 standards, test site information, and environmental conditions like wind speed, air temperature, wind direction, barometric pressure, and humidity It should specify the measuring equipment used, including the windscreen, and record the background noise level measured in A-weighted sound pressure levels The report must identify the vehicle, detailing its engine, transmission system with ratios, tyre size and type, tyre pressure and production, power, test mass, power-to-mass ratio, and vehicle dimensions It should also specify the transmission gears or ratios employed during the test, along with vehicle and engine speeds at the start and end of acceleration, including the location where acceleration begins Calculation methods for acceleration, auxiliary equipment, and operating conditions should be documented Finally, all valid A-weighted sound pressure level measurements must be listed, distinguished by the vehicle side and movement direction during testing.
Technical background for development of vehicle noise test procedure based on in-use operation in urban conditions
This annex offers technical background on the development of the vehicle noise testing procedure, based on real-world in-use data It includes examples from actual in-use studies to illustrate the process, while not revealing the complete in-use databases.
The procedure outlined in ISO 362 measures vehicle noise emissions that vehicle manufacturers can control However, other significant factors affecting traffic noise, such as road surfaces, traffic regulations, and aftermarket parts, are outside the manufacturer's influence Effective traffic noise management also depends on in-use noise emission monitoring and strong enforcement mechanisms to address external contributors.
A.2 The need for a new test procedure
The current regulation procedure for vehicle noise measurement is outlined in ISO 362:1998, which specifies testing on a designated surface in accordance with ISO 10844 During testing, the vehicle accelerates with wide-open throttle in second and/or third gear, approaching the microphone at a speed of 50 km/h from 10 meters away The measured sound pressure level reflects the noise produced in a single gear test, with the final value being the average of second and third gear measurements This standardized procedure has contributed to a significant reduction in regulatory noise limits, decreasing from 86 dB in 1980 to 80 dB by 1999 within the European Union.
The current noise test procedure for motorcycles, outlined in ISO 362:1998, is widely recognized within the legislative and motorcycle industries as inadequate, as it fails to accurately replicate real-world motorcycle behavior Additionally, its lack of robustness in cycle-bypassing and sub-optimization compromises the reliability of noise measurements This ongoing concern underscores the need for improved testing standards to ensure more accurate assessments of motorcycle noise emissions.
Recent in-use data indicates that most motorcycle operation involves partial throttle rather than wide-open throttle To accurately simulate real-world conditions, the new noise test procedure uses mathematical interpolation between wide-open throttle and steady-state, constant speed tests This approach addresses the control challenges of replicating partial throttle acceleration, focusing on test conditions that reflect typical urban motorcycle usage By selecting test parameters aligned with vehicle acceleration capabilities and engine speeds common in urban environments, the procedure ensures consistency, repeatability, and comparability across different motorcycle types.
A.3 In-use data collection and analysis
The vehicle noise depends mainly on three vehicle parameters:
3) engine speed n (for internal combustion engines only)
Tyre and road noise are influenced by vehicle speed and acceleration, with noise levels increasing alongside higher speeds and rapid acceleration In category L vehicles, tyre/road noise can be considered negligible due to their typically lower speeds Vehicle speed and acceleration not only reflect driving behavior but are also affected by driver commands, vehicle performance, and the surrounding traffic environment, highlighting the complex interplay of factors that contribute to noise generation.
The third key parameter, engine speed, is influenced by vehicle acceleration and overall vehicle speed Therefore, urban traffic studies must independently analyze vehicle speed and acceleration to accurately understand engine performance and traffic flow dynamics.
A comprehensive study of real-world urban motorcycle driving was conducted, focusing on collecting in-use data related to vehicle and engine speeds This data was essential for developing the Worldwide Motorcycle Exhaust Emission Test Cycle (WMTC) under the UN Economic Commission for Europe Additionally, supplementary data was gathered specifically to create a new noise test procedure, ensuring accurate and representative testing methods for motorcycle emissions and noise levels in urban environments.
In-use data was collected in locations throughout Europe, Asia and the US with the following particulars:
⎯ 43 vehicles (11 in Europe; 5 in the US; 27 in Asia);
To ensure optimum consistency with the WMTC development process, the same driving module characterization criteria were used as shown in Table A.1
Table A.1 — Characterization criteria for driving modules
Allocation of driving Part 1 0 km/h to 60 km/h W 80 %
90+ km/h = 0 % v max u 80 km/h Additionally: length of sequence W 1 m
A primary goal was to develop a new noise test procedure that accurately mimics typical motorcycle operating conditions, especially when motorcycles are in close proximity to the majority of the population Consequently, the focus was placed on analyzing the Part 1 driving modules, which represent the most relevant operational scenarios Using the characterization criteria outlined in Table A.1, a total of 5,978 Part 1 driving modules were identified, covering a total driving distance of 3,965 kilometers.
Analysis of these modules resulted in the following median vehicle speeds:
50 km/h for PMR > 50 These median vehicle speeds defined the following vehicle speed windows:
The in-use data was analyzed within specific time windows, focusing on engine speed ratio (n/S 95) and urban traffic acceleration (a_urban) The analysis examined how these parameters vary as a function of the power-to-mass ratio, with detailed results illustrated in Figures A.1 and A.2.
PMR power-to-mass ratio
(n/S) 95 95th percentile engine speed ratio
PMR power-to-mass ratio a urban urban traffic acceleration
Figure A.2 — Regression curve a urban = f(PMR)
A.4 Determination of wide-open-throttle acceleration
A relationship was established between vehicle acceleration and the power-to-mass ratio by analyzing the connection between engine speed ratio and power-to-mass ratio This new noise test procedure is designed to be independent of engine speed, ensuring its applicability across various propulsion technologies, including electric and alternative power sources, not limited to internal combustion engines.
To this end, test track measurements were performed on 36 motorcycles with wide-open-throttle acceleration