GB/T 22036-2017Coast-by methods for measurement of tyre-to-road sound emission (English PDF)

7.1 Acoustic Measuring Instruments

The sound level meter or equivalent measuring system, including the windproof cover recommended by the microphone manufacturer, shall meet the minimum requirements for Type

1 equipment in IEC 61672-1 or IEC 61672-3.

Measurements shall be performed using “A” frequency weighting characteristics and “F” time weighting characteristics.

At the start of the measurement, the sound level meter shall be calibrated and recorded using a standard sound source (for example, a piston generator) in accordance with the instrument manufacturer’s instructions. At the end of the test, the sound level meter shall be calibrated and recorded again. The sound calibrator shall meet the requirements for Type 1 equipment in IEC

60942.

During measurement, if the sound level meter readings obtained from a series of measurement calibrations differ by more than 0.5 dB, the tests during that period shall be considered invalid.

Any deviation shall be recorded in the test report.

The sound level meter shall be submitted for inspection in accordance with the requirements of

IEC 61672-1 and IEC 61672-3, and the metrological calibration cycle shall not exceed 2 years.

The sound calibrator shall be submitted for inspection in accordance with the requirements of

IEC 60942, and the metrological calibration cycle shall not exceed 1 year.

The microphones shall be equipped with a windproof cover, and the use of the windproof cover shall meet the requirements of the microphone manufacturer.

When it cannot be confirmed whether the sound level meter model conforms to all specifications of IEC 61672-1, the sound level meter or equivalent measurement system used for measurement shall conform to the requirements for Type 1 equipment in IEC 61672-3.

NOTE. the tests in IEC 61672-3 only cover a finite subset of the specifications in IEC 61672-1, which has a relatively wide scope (temperature range, frequency requirements up to 20 kHz, etc.). From an economic perspective, it is not feasible to verify every item of a computerized data acquisition system model against the requirements of IEC 61672-1.

Currently, no commercially available computer-based data acquisition system fully meets all the requirements of IEC 61672-1.Furthermore, this does not mean that the user needs to prove that these systems meet the equipment requirements in accordance with the test requirements.

7.2 Microphones

Two microphones shall be used in the test, one on each side of the vehicle. There shall be no reflective objects affecting the sound field near the microphones, and no person or object shall be left between the microphones and the sound source. Test personnel shall be in a location that does not interfere with the acoustic testing, and in particular, they shall not be positioned within the test area.

The microphones shall be positioned 7.5 m ± 0.05 m from the centerline of driving of the test vehicle and 1.2 m ± 0.02 m above the ground. In addition, it shall be determined by the sound level meter manufacturer’s requirements based on the actual position of the test vehicle when it passes through the centerline of driving as shown in Figure 1.

7.3 Temperature Measurement

7.3.1 General rules

For both air and test road surface temperatures, the accuracy of the temperature measuring instrument shall be within ± 1 °C. Infrared temperature measuring instruments shall not be used to measure air temperature.

Continuous temperature recording is possible through instruments and equipment; if not, single-value measurements and recordings can be performed.

Air and road surface temperatures shall be measured, and the measuring instruments shall be used in accordance with the instrument manufacturer’s instructions.

Temperature measurements shall be performed throughout the entire noise measurement process, or the average value of the initial and final test temperatures shall be used.

7.3.2 Air temperature

Place the temperature sensor near the microphones in an unobstructed location, exposed to airflow. A sunshade or similar device may be used to avoid direct sunlight. The temperature sensor shall be located 1.2 m ± 0.1 m above the test road surface to minimize the impact of thermal radiation from the test road surface caused by low airflow (too low wind velocity).

7.3.3 Test road surface temperature

Install the temperature sensor at a location that allows measurement of the temperature of the wheel tracks without obstructing tyre noise measurements.

If a contact-type temperature sensor is used, a thermally conductive adhesive shall be used between the road surface and the sensor to ensure sufficient heat conduction.

If a radiation-type thermometer is used, the height shall be chosen to ensure coverage of the measurement area within a range of at least 0.1 m from the thermometer diameter.

Before or during the test, artificial cooling of the test road surface shall not be performed.

7.4 Wind Velocity Measurement

The anemometer accuracy shall be within ±1 m/s. The anemometer shall be placed between points A-A and B-B, no more than 20 m from the centerline of driving (see Figure 1), at the same height as the microphones. Meanwhile, the wind direction relative to the driving direction shall also be recorded.

7.5 Velocity Measurement

The velocity measuring device shall be able to measure the velocity of the test vehicle, and the error shall not exceed ± 1 km/h.

8.1 Meteorological Conditions

Measurements shall not be conducted under extreme weather conditions and shall not be affected by gusts. During testing, the wind velocity at the microphone height shall not exceed

5 m/s.

Tests shall be conducted within an air temperature range of 5 °C to 40 °C and a road surface temperature range of 5 °C to 50 °C.

......