I reduce wind noise in my bike helmet with "No Noise" earplugs.
It is like a normal ear plug but has a ceramic insert which filters noise.

They are quite cheap at around R250 a set and fully washable for multiple use or
use by different people.

Google them. You'll be surprised!

Hi Pieter and T-bird.

I Thought this video sums up the situation of "behind the power curve" very well !

"Dons Calidus autogyro first flight at SCCMAS" on youtube