It can be quite annoying to have a foil set up that keeps making a humming noise after a certain speed. Your ride is still fine but it sure is annoying. I had such a set up and tried to find out why or what makes my set up humm.
I cycled through all my stabilizers even using different fuselage and mast. It was not an easy task and the answer ist not 100% conclusive, but I found out quite a bit on the way.
In this video you can come on this journey with me.