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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 22036-2008 Coast-by methods for measurement of tyre-to-road sound emission, and the following main technical changes have been made with respect to GB/T 22036-2008:
—— Sub-clause 3.1 in 2008 Edition is deleted;
—— Sub-clause 3.2 in 2008 Edition is deleted;
—— The requirement “Windscreens shall be used when the wind speed reaches 2 m/s or more” is added (see Sub-clause 6.1);
—— The test range that requires at least 20m is added (see Sub-clause 6.2);
—— "Sound Pressure Level A" is changed to "sound pressure level corresponding to the frequency of each one-third frequency band center" (see Sub-clause 7.2);
—— Test surface verification is added (see Clause 9);
—— The content “Deviation of left and right tyre loads shall be less than 10%” is added. [See Sub-clause A.1.4 c)];
—— The test report and examples of test records are deleted (see Sub-clauses A.3 and B.5 in 2008 Edition).
This standard has been redrafted and modified adoption of International Standard ISO 13325:2003 Tyres - Coast-by methods for measurement of tyre-to-road sound emission (English version).
Technical deviations between this standard and the International Standard ISO 13325:2003 and their justifications are as follows:
—— The adjustments of technical difference are made for the normative references in this standard so as to adapt to the technical conditions in China. The adjustment conditions are mainly reflected in Clause 2 "Normative references"; the specific adjustments are as follows:
GB/T 3785.1-2010 identical to the international standard is used to replace ISO 60651:2001 sound-level meter; see Sub-clause 6.1);
GB/T 6326 non-equivalent to the international standard is used to replace ISO 4223-1 (see Clause 3);
GB/T 15173-2010 identical to the international standard is used to replace IEC 60942:1997 (see Sub-clause 6.1);
Referenced document ISO 362.1:2015 is added (see Clause 5).
—— Sub-clause 3.1 is deleted and directly described by definition in the text;
—— Sub-clause 3.2 is deleted as the term is already in GB/T 6326.
—— The requirement “Windscreens shall be used when the wind speed reaches 2m/s or more” is added (see Sub-clause 6.1) to minimize the influence on the test results;
—— The test range that requires at least 20m (see Sub-clause 6.2) is added to avoid influence on test results;
—— "Sound Pressure Level A" is changed to "sound pressure level corresponding to the frequency of each one-third frequency band center" (see Sub-clause 7.2) as such expression is more accurate;
—— Test surface verification is added (see Clause 9) to ensure more accurate test conditions;
—— “Deviation of left and right tyre loads” shall be less than 10%” is added to ensure more accurate test results. [See A.1.4 c)];
—— The test report and examples of test records are deleted (see Sub-clauses A.3 and B.5 in 2008 Edition). It is quite feasible to design test report and test record table according to the contents of requirements.
The following editorial changes have been made in this standard:
—— the standard name is modified;
—— the bibliography is deleted.
This standard was proposed by China Petroleum and Chemical Industry Association.
This standard is under the jurisdiction of the National Technical Committee on Tyres and Rims of Standardization Administration of China (SAC/TC 19).
The previous edition replaced by this standard is as follows:
—— GB/T 22036-2008.
Coast-by methods for measurement of tyre-to-road sound emission
1 Scope
This standard specifies methods for measuring tyre-to-road sound emissions from tyres fitted on a motor vehicle or towed trailer under coast-by conditions, i.e. when the vehicle or trailer is in free-rolling, non-powered operation, with transmission in the neutral position and the engine as well as all auxiliary systems not necessary for safe driving switched off. Whereas the results of the vehicle method are closer to the tyres sound than those of hat the trailer method, the tyre sound is affected by suspension; the test results of trailer method can be even closer to sound emissions produced by the tyres alone.
This standard is applicable to new tyres of passenger cars and trucks. It is neither applicable to determine the sound contribution (sound field distribution) of tyres of vehicles running in normal condition nor to the determination of traffic sound and its damage degree at a given location.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 3785.1-2010 Electroacoustics - Sound level meters - Part 1 Specification (IEC 61672-1:2002, IDT)
GB/T 6326 Tyre terms and definitions (GB/T 6326-2014, ISO 4223-1:2002, Definitions of some terms used in tyre industry - Part 1: Pneumatic tyres, NEQ)
GB/T 15173-2010 Electroacoustics - Sound calibrators (IEC 60942:2003, IDT)
ISO 362.1 Measurement of noise emitted by accelerating road vehicles - Engineering method - Part 1: M and N categories
ISO 10844 Acoustics - Specification of test tracks for measuring noise emitted by road vehicles and their tyres
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 6326 apply.
4 General
This standard is applicable to measurement of sound emitted from the tyre of a test motor vehicle (see Annex A) or trailer (see Annex B) in coast-by conditions.
The test results are an objective measure of the sound emitted under the prescribed conditions of the test, i.e. A-weighted sound pressure level.
5 Test site
The test site shall be a semi-free acoustical field consisting of a substantially flat and level area. Conditions of the acoustical field are: a non-directional sound source is placed in the center of the site, and the sound pressure deviation in all directions on the hemisphere surface shall not exceed ±1dB. These conditions shall be deemed to be met if there is no large sound reflecting object, such as fences, rocks, bridges or buildings, within 50m of the center of the test area.
The test surface, including voids, shall be dry and clean for all measurements. The test area and surface shall meet the requirements of ISO 10844. The measurement zone and the microphone location are shown in Figure 1.
Keys:
● —— the microphone location (1.2 m high);
CC′ —— the centerline of travel;
ls —— the length of acceleration zone;
la ——the length of steady speed driving zone (test extension zone);
Light gray zone: extension zone;
Deep gray zone with dotted line: test track.
Figure 1 Plan dimensions of test site
In Figure 1, on the outer sides of A-A and B-B are stable speed driving tracks with the length of la and the width of at least 3 m. The selection of la value is shown in Table 1. It is recommended that the length of acceleration zone ls of the test be at least 60 m.
Table 1 Minimum extension length of driving tracks
Length Rear engines with a distance of more than 10 m between the reference point and the front axle
Extended vehicles (reference point is defined in ISO 362-1) Other vehicles
la 20 ma 10 m
a The distance between both ends of the two-way driving test site is 20 m; the approach section of one-way driving test site can also be 10 m, and the exit section is 20 m.
6 Instrumentation
6.1 Instrumentation for acoustical measurements
The sound pressure level meter or equivalent measuring system (including anti-wind ball) shall at least meet the requirements of Type 1 instrument in accordance with GB/T 15173-2010.
The measurements shall be made using the “A” frequency-weighted characteristic, and “F” time-weighted characteristic.
The calibration of the sound pressure level meter shall be checked and adjusted in accordance with the manufacturer’s instructions or with a standard sound source (e.g. pistonphone) at the beginning of the measurements and rechecked and recorded at the end of them. The calibration device shall meet the requirements of Class 1 in accordance with GB/T 15173-2010.
If the sound pressure level meter indications obtained from these calibrations differs by more than 0.5dB during a series of measurements, the test shall be considered invalid. Any deviation shall be recorded in the test report.
At intervals of not more than one year, the sound pressure level meter and the calibration device shall be verified with the requirements of GB/T 3785.1-2010 and GB/T 15173-2010.
Windscreens shall be used when the wind speed reaches 2 m/s or more.
The test area and surface shall be in accordance with ISO 10844, as shown in Figure 1. Additionally, there shall be no large acoustically reflective objects within the radius shown in Figure 1.
6.2 Microphones
Two microphones shall be used in the test, one on each side of the vehicle/trailer. In the vicinity of the microphones, there shall be no obstacle that could influence the acoustical field and no person shall remain between the microphones and the sound source. Any observer or observers shall be positioned at least 20 m away from the microphone so as not to influence the measurement result of the instrument.
The distance from the microphone positions to the centerline of travel on the test track shall be (7.5 ± 0.05) m. Each microphone shall be located (1.2 ± 0.02) m above the test area surface. The reference axis shall be horizontal and vertically directing to the centerline of travel.
6.3 Temperature measurement
6.3.1 General
For air as well as test surface temperature, the measuring instrument shall have an overall accuracy within ±1℃. Meters utilizing the infrared technique shall not be used for air temperature measurements.
The type of sensor shall be reported.
Continuous record of temperature via instruments may be employed. If such an option is not available, single values are to be measured and recorded.
Measurements of air as well as test surface temperatures are mandatory. The final results are the readings rounded to the nearest integer in degrees Celsius.
Temperature measurements shall correspond reasonably over time with sound measurements of tyres in both vehicle and trailer methods. Alternatively, the average of the temperature at the beginning and the end of the set of tests may be used in both methods.
6.3.2 Air temperature
Position the temperature sensor in an unobstructed and sheltered location close to the microphone, such that it is exposed to the airflow and protected from direct solar radiation. The latter may be achieved by any shading screen or similar device. The sensor shall be positioned 1.2 m±0.1m above the test surface level, to minimize the influence of low airflows caused by test surface thermal radiation.
6.3.3 Test surface temperature
Position the temperature sensor in a location where the temperature is representative of the temperature in the wheel tracks, without interfering with the sound measurement.
If an instrument with a contact temperature sensor is used, apply heat-conductive paste between the surface and the sensor to ensure adequate thermal contact.
If a radiation thermometer is used, the height shall be chosen to ensure that a measuring spot with a diameter of ≥0.1 m is covered.
The test surface shall not be artificially cooled during or prior to testing.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General
5 Test site
6 Instrumentation
7 Meteorological conditions and background sound
8 Preparation and adjustments with respect to tyres
9 Test surface verification
Annex A (Normative) Vehicle method
Annex B (Normative) Trailer method
轮胎惯性滑行通过噪声测试方法
1 范围
本标准规定了在惯性滑行条件下，测量安装在试验车辆或拖车上轮胎噪声的测试方法。惯性滑行是指发动机关闭，没有动力驱动、变速器空挡和试验轮胎处于自由滚动状态的条件。车辆法比拖车法轮胎噪声测试结果更接近实际效果，但轮胎噪声受悬架参数的影响；拖车法测试结果更接近单个轮胎实际产生的噪声。
本标准适用于新的轿车轮胎和载重汽车轮胎。既不适用于测量车辆在正常行驶条件下轮胎噪声（声场分布），也不适用于测量车辆在正常行驶条件下给定位置上的交通噪声及危害程度。
2 规范性引用文件
下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本（包括所有的修改单）适用于本文件。
GB/T 3785.1—2010 电声学 声级计 第1部分：规范（IEC 61672-1：2002，IDT）
GB/T 6326 轮胎术语及其定义（GB/T 6326—2014，ISO 4223-1：2002，Definitions of some terms used in tyre industry—Part 1：Pneumatic tyres，NEQ）
GB/T 15173—2010 电声学 声校准器（IEC 60942：2003，IDT）
ISO 362.1 加速道路车辆辐射噪声测量工程法第1部分：M和N类（Measurement of noise emitted by accelerating road vehicles—Engineering method—Part 1：M and N categories）
ISO 10844 声学 测量道路车辆噪声用试验路面的规定（Acoustics—Specification of test tracks for measuring noise emitted by road vehicles and their tyres）
3 术语和定义
GB/T 6326界定的术语及定义适用于本文件。
4 总则
本标准适用于试验车辆（见附录A）或拖车（见附录B）在惯性滑行条件下测量轮胎噪声。
试验结果是在规定试验条件下测得的轮胎噪声客观量，即A声级。
5 试验场地
试验场地应由连续的水平区域组成一个半自由声场。试验场地应达到的声场条件是：在该场地的中心放置一个无指向小声源时，半球面上各方向的声压级偏差不超过±1 dB。应满足在试验区域中心50 m以内的范围内没有大的声音反射物体的条件，如：栅栏、岩石、桥梁或建筑物等。
试验路面（包括孔隙），在整个测量过程中应该是干燥、清洁的，试验区域和道路表面应符合ISO 10844的要求。测量区域和传声器位置如图1所示。
说明：
●——传声器位置（高度1.2 m）；
CC′——行驶中心线；
ls——加速区长度；
la——稳定速度行驶区（试验延长区）长度；
浅灰色区域：扩展区；
带虚线的深灰色区域：试验车道。
图1 试验场地平面尺寸图
图1中在A—A、B—B外侧是长度为la和至少3 m宽的稳定速度行驶车道。la值的选取如表1所示。建议试验场加速区长度ls至少为60 m。
表1 行车车道最小延伸长度
长度 参考点与前桥之间的距离超过10 m的后置发动机
加长型车辆（参考点在ISO 362-1中定义） 其他车辆
la 20 ma 10 m
a 双向行驶试验场两端距离均为20 m；单向行驶试验场进场段也可以为10 m，出场区段为20 m。
6 测量仪器
6.1 声学测量仪器
声级计或等效的测试系统（包括防风球）应至少符合GB/T 15173—2010中对第1类型设备的要求。
测量应使用“A”频率计权特性和“F”时间计权特性。
测量开始时，声级计的校准应按照仪器生产厂的说明书进行检查和调节，并用标准声源（如活塞发生器）进行校准，试验结束时重新检查和记录。校准设备应符合GB/T 15173—2010中相应的第1类型规定的要求。
在进行测量时，如果通过校准的声级计每次测得的数据误差（变化范围）超过0.5 dB，该试验视为无效，校准时的读数应记录在试验报告中。
声级计和校准设备应该在间隔不超过1年的时间内根据GB/T 3785.1—2010和GB/T 15173—2010的要求进行检验。
当风速达到2 m/s以上时，传声器应使用防风罩。
试验场地和表面应符合ISO 10844要求，如图1所示，另外，在图1所示的半径范围内没有声学反射物。
6.2 传声器
试验中使用2个传声器，车辆（或拖车）的两侧各1个，在传声器附近，应该没有声反射物，并且声源与传声器之间没有任何人站留。进行测量的观察者也应站在距传声器至少20 m外不致影响仪器测量结果的位置。
传声器应该布置在离地面高1.2 m±0.02 m，距离车辆行驶中心线7.5 m±0.05 m处，其参考轴线应保持水平并垂直指向车辆行驶中心线。
6.3 温度测量
6.3.1 总论
对于空气和试验路面温度，温度计或其他温度测量仪的精度应该在±1℃以内。红外温度测量仪不能用来测量空气温度。
应记录所使用的温度传感器类型。
可以通过仪器设备对温度进行连续记录。如果条件不允许，也可以进行单值测量和记录。
空气温度和试验路面温度测量是强制性的，最后读数近似到实际测得值的摄氏度整数位。
无论是车辆法还是拖车法，温度测量应该是贯穿轮胎噪声测量的全过程，或者使用试验开始和结束时的温度的平均值。
6.3.2 空气温度
将温度传感器置于传声器附近有遮挡的地方，例如：暴露在气流下，不受太阳光直射，可以采用遮阳屏或类似装置达到同样效果。温度传感器应位于距试验路面上方1.2 m±0.1 m的地方，以减少试验路面热辐射引起的低气流影响。
6.3.3 试验路面温度
将温度传感器置于能够测得代表车轮印迹温度的位置，同时不妨碍轮胎噪声的测量。
如果使用接触式的温度传感器，应该在路面和传感器之间使用导热性能好的粘接剂，以确保足够的热传导。
如果使用热辐射温度计，高度的选择应确保覆盖测量场地距温度计直径≥0.1 m的范围。
试验路面在试验前及试验中不应进行人工冷却。
6.4 风速的测量
风速仪的精度应该在±1 m/s以内。风速仪应该在传声器高度、在A—A和B—B之间、距行驶中心线不超过20 m（见图1）的位置，并同时记录风向。
6.5 速度的测量
速度测量装置应该能测试试验车辆或拖车的速度，并保证误差在±1 km/h以内。
7 气象条件和背景噪声
7.1 气象条件
测量应在良好天气条件下进行。测试时，传声器高度的风速不应该超过5 m/s。当空气温度在5℃～40℃范围内或路面温度为在5℃～50℃范围内时，可以进行试验。应注意测量结果不受阵风的影响。
