In the wind tunnel, the base and modified parts were installed on an EV (Hyundai Motor Company) to measure the cabin noise intercepted by the driver's inner ear and the proximity sound at a distance of 100 mm at a wind speed of 110 kph and a yaw angle of 10. Consequently, it was confirmed that the noise was improved to the level of 1.0 dB(A) and 1.2 dB(A) for the cabin noise and proximity noise, respectively (Figure 19). Vehicles of the same model were evaluated at Hyundai Motor Group California Proving Ground, USA. The crosswind speed was 32 kph, which was a suitable weather environment to test the fluctuation sound owing to wind variability. At 130 kph, both the cabin and proximity noise were measured in the same manner as in the wind tunnel test, and the improvement was clearly seen at a high frequency (2–8 kHz) area (Figure 20).