It doesn't matter how "white" the noise is, what matters is the volume. A jet engine is pretty close to white noise, it's just really fucking loud. We accept jets because they usually are 5+ miles above us. These flying cars are meant to fly a few hundred feet above the ground.

My hunch, although nobody can say definitively, is it is physically impossible to make these quiet enough to be acceptable for mass use. But aerodynamics has as much trial-and-error as it does theory so maybe a genius will come up with something novel.