The noise measurement is carried out on a noise test track which satisfies the ISO 10844 requirements. The 2 microphones are positioned at 7.5 m distance from the track centerline (both sides) and 1.20 m height over the measurement surface. Both microphones are calibrated on site before the testing start. For the measurements, the vehicle is driven on the measurement surface with the engine switched off and the gear in neutral position. The sound pressure levels (SPL) in dB (A) are measured by both left and right microphones together with the vehicle speed. For each run the maximum SPL between the entrance gate (10m before the microphones line) and the exit gate (10m after) are recorded. Those recording are carried out 8 times at different speeds between 70 and 90 km/h; the different speeds are distributed as evenly as possible across the defined speed range. Regression analysis is used to establish the relationship between the results and the reference speed of 80 km/h.
