Noise cars windows make when half down ??

Question

Whats up with that noise car windows make when their like half down its mostly the ones in the back seat it sounds like a helicopter it kinda hurts the ears too how is that caused ?

Answer 1

because the flow pattern of the air is unstable and causes fluctuations/pulses.

allowing more or less air in may cause the air to circulate more freely, but if it's open a certain amount (depending on the aerodynamics of the car), there may be less steady circulation.

when the circulation isnt steady, the opposing air flows fluctuate back and forth causing the vibrations that you hear