In vehicle development, noise reduction is critical for ensuring passenger comfort. As electric
vehicles become prevalent and engine noise is minimized, wind noise becomes more noticeable.
Modulated wind noise, which causes a sense of fluctuation due to atmospheric turbulence,
wind gusts, and preceding vehicle wakes, causes significant discomfort. This noise is
characterized as a high-frequency sound above 1 kHz, modulated at low frequencies owing to
the wind velocity and direction fluctuating at several Hz. However, the mechanisms behind
wind noise modulation are not fully understood, and no established countermeasures have
been developed. This is because wind noise perceived through the side window is primarily
caused by the A-pillar vortex and door mirror wake, which coexist as complex turbulent flows
around the vehicle. Therefore, identifying the source of modulated wind noise around vehicles
under fluctuating wind conditions is difficult. This study aims to identify the source of the
modulated wind noise and to clarify the underlying flow mechanisms. Numerical analysis
(CFD) simulated windy conditions, where the wind velocity and direction fluctuated at several
Hz, successfully reproducing modulated wind noise around the vehicle. Using the modulation
power spectrum to quantitatively evaluate the modulated wind noise, the contributions of Apillar
separation and door mirror wake to modulation power were clarified, identifying the
source of the modulated wind noise around the vehicle. Additionally, we examined vehicle
shape effects, such as door mirror presence and A-pillar modifications, which can suppress
modulated wind noise. No significant difference in wind noise modulation power was observed
with or without door mirrors, but it was found that the A-pillar shape modification contributed
significantly to high-frequency noise modulation power. To suppress modulated wind noise,
designing an A-pillar shape that minimizes the separation flow, which intensifies owing to
crosswind fluctuations, is crucial.