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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
輪胎慣性滑行通過噪聲測試方法
1 范圍
本標準規定了在慣性滑行條件下，測量安裝在試驗車輛或拖車上輪胎噪聲的測試方法。慣性滑行是指發動機關閉，沒有動力驅動、變速器空擋和試驗輪胎處于自由滾動狀態的條件。車輛法比拖車法輪胎噪聲測試結果更接近實際效果，但輪胎噪聲受懸架參數的影響；拖車法測試結果更接近單個輪胎實際產生的噪聲。
本標準適用于新的轎車輪胎和載重汽車輪胎。既不適用于測量車輛在正常行駛條件下輪胎噪聲（聲場分布），也不適用于測量車輛在正常行駛條件下給定位置上的交通噪聲及危害程度。
2 規范性引用文件
下列文件對于本文件的應用是必不可少的。凡是注日期的引用文件，僅注日期的版本適用于本文件。凡是不注日期的引用文件，其最新版本（包括所有的修改單）適用于本文件。
GB/T 3785.1—2010 電聲學 聲級計 第1部分：規范（IEC 61672-1：2002，IDT）
GB/T 6326 輪胎術語及其定義（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 電聲學 聲校準器（IEC 60942：2003，IDT）
ISO 362.1 加速道路車輛輻射噪聲測量工程法第1部分：M和N類（Measurement of noise emitted by accelerating road vehicles—Engineering method—Part 1：M and N categories）
ISO 10844 聲學 測量道路車輛噪聲用試驗路面的規定（Acoustics—Specification of test tracks for measuring noise emitted by road vehicles and their tyres）
3 術語和定義
GB/T 6326界定的術語及定義適用于本文件。
4 總則
本標準適用于試驗車輛（見附錄A）或拖車（見附錄B）在慣性滑行條件下測量輪胎噪聲。
試驗結果是在規定試驗條件下測得的輪胎噪聲客觀量，即A聲級。
5 試驗場地
試驗場地應由連續的水平區域組成一個半自由聲場。試驗場地應達到的聲場條件是：在該場地的中心放置一個無指向小聲源時，半球面上各方向的聲壓級偏差不超過±1 dB。應滿足在試驗區域中心50 m以內的范圍內沒有大的聲音反射物體的條件，如：柵欄、巖石、橋梁或建筑物等。
試驗路面（包括孔隙），在整個測量過程中應該是干燥、清潔的，試驗區域和道路表面應符合ISO 10844的要求。測量區域和傳聲器位置如圖1所示。
說明：
●——傳聲器位置（高度1.2 m）；
CC′——行駛中心線；
ls——加速區長度；
la——穩定速度行駛區（試驗延長區）長度；
淺灰色區域：擴展區；
帶虛線的深灰色區域：試驗車道。
圖1 試驗場地平面尺寸圖
圖1中在A—A、B—B外側是長度為la和至少3 m寬的穩定速度行駛車道。la值的選取如表1所示。建議試驗場加速區長度ls至少為60 m。
表1 行車車道最小延伸長度
長度 參考點與前橋之間的距離超過10 m的后置發動機
加長型車輛（參考點在ISO 362-1中定義） 其他車輛
la 20 ma 10 m
a 雙向行駛試驗場兩端距離均為20 m；單向行駛試驗場進場段也可以為10 m，出場區段為20 m。
6 測量儀器
6.1 聲學測量儀器
聲級計或等效的測試系統（包括防風球）應至少符合GB/T 15173—2010中對第1類型設備的要求。
測量應使用“A”頻率計權特性和“F”時間計權特性。
測量開始時，聲級計的校準應按照儀器生產廠的說明書進行檢查和調節，并用標準聲源（如活塞發生器）進行校準，試驗結束時重新檢查和記錄。校準設備應符合GB/T 15173—2010中相應的第1類型規定的要求。
在進行測量時，如果通過校準的聲級計每次測得的數據誤差（變化范圍）超過0.5 dB，該試驗視為無效，校準時的讀數應記錄在試驗報告中。
聲級計和校準設備應該在間隔不超過1年的時間內根據GB/T 3785.1—2010和GB/T 15173—2010的要求進行檢驗。
當風速達到2 m/s以上時，傳聲器應使用防風罩。
試驗場地和表面應符合ISO 10844要求，如圖1所示，另外，在圖1所示的半徑范圍內沒有聲學反射物。
6.2 傳聲器
試驗中使用2個傳聲器，車輛（或拖車）的兩側各1個，在傳聲器附近，應該沒有聲反射物，并且聲源與傳聲器之間沒有任何人站留。進行測量的觀察者也應站在距傳聲器至少20 m外不致影響儀器測量結果的位置。
傳聲器應該布置在離地面高1.2 m±0.02 m，距離車輛行駛中心線7.5 m±0.05 m處，其參考軸線應保持水平并垂直指向車輛行駛中心線。
6.3 溫度測量
6.3.1 總論
對于空氣和試驗路面溫度，溫度計或其他溫度測量儀的精度應該在±1℃以內。紅外溫度測量儀不能用來測量空氣溫度。
應記錄所使用的溫度傳感器類型。
可以通過儀器設備對溫度進行連續記錄。如果條件不允許，也可以進行單值測量和記錄。
空氣溫度和試驗路面溫度測量是強制性的，最后讀數近似到實際測得值的攝氏度整數位。
無論是車輛法還是拖車法，溫度測量應該是貫穿輪胎噪聲測量的全過程，或者使用試驗開始和結束時的溫度的平均值。
6.3.2 空氣溫度
將溫度傳感器置于傳聲器附近有遮擋的地方，例如：暴露在氣流下，不受太陽光直射，可以采用遮陽屏或類似裝置達到同樣效果。溫度傳感器應位于距試驗路面上方1.2 m±0.1 m的地方，以減少試驗路面熱輻射引起的低氣流影響。
6.3.3 試驗路面溫度
將溫度傳感器置于能夠測得代表車輪印跡溫度的位置，同時不妨礙輪胎噪聲的測量。
如果使用接觸式的溫度傳感器，應該在路面和傳感器之間使用導熱性能好的粘接劑，以確保足夠的熱傳導。
如果使用熱輻射溫度計，高度的選擇應確保覆蓋測量場地距溫度計直徑≥0.1 m的范圍。
試驗路面在試驗前及試驗中不應進行人工冷卻。
6.4 風速的測量
風速儀的精度應該在±1 m/s以內。風速儀應該在傳聲器高度、在A—A和B—B之間、距行駛中心線不超過20 m（見圖1）的位置，并同時記錄風向。
6.5 速度的測量
速度測量裝置應該能測試試驗車輛或拖車的速度，并保證誤差在±1 km/h以內。
7 氣象條件和背景噪聲
7.1 氣象條件
測量應在良好天氣條件下進行。測試時，傳聲器高度的風速不應該超過5 m/s。當空氣溫度在5℃～40℃范圍內或路面溫度為在5℃～50℃范圍內時，可以進行試驗。應注意測量結果不受陣風的影響。
