Vibrava

In Astra, Vibrava has a Bug/Steel-type regional form. It evolves from Astrian Trapinch starting at level 35 and evolves into Astrian Flygon starting at level 45.

By controlling the rate at which it flaps it wings, it can buzz at almost any frequency. By increasing this frequency to a range imperceptible to humans and most Pokémon, it can fly completely silently.