1. Measuring instruments
1. Use a precision sound level meter or a normal sound level meter and engine tachometer.
2. The sound level meter error should not exceed ±2dB (A).
3. Before and after measurement, the instrument should be calibrated as specified.
2. Exterior noise measurement
(1) Measurement conditions
4. The measurement site should be flat and open, and there should be no large reflectors, such as buildings, walls, etc., within a radius of 25m from the test center.
5. The runway of the test site should have a straight, dry asphalt road or concrete road with a length of more than 20m. The slope of the road surface shall not exceed 0.5%.
6. The noise floor (including wind noise) should be at least 10 dB(A) lower than the measured vehicle noise. And ensure that the measurement is not disturbed by accidental other sound sources.
Note: The noise floor refers to the noise of the surrounding environment when the noise of the measurement object does not exist.
7. In order to avoid wind noise interference, a windshield can be used, but attention should be paid to the influence of the windshield on the sensitivity of the sound level meter.
8. In addition to the measurer, there should be no other personnel near the sound level meter. If it is indispensable, it must be behind the measurer.
9. The vehicle under test is not loaded. The engine should be at normal operating temperature during the measurement, and other auxiliary equipment in the vehicle is also a source of noise.
10. The test microphones are located on both sides of the center point 0 of the 20m runway, 7.5m away from the center line and 1.2m above the ground, and fixed with a tripod. The microphones are parallel to the road surface and their axes are perpendicular to the direction of the vehicle.
