Trailing and leading edge serrations

Owl-inspired leading-edge serrations play a crucial role in aerodynamic force production and sound suppression

(But here is a different explanation for owls’ silent flight: Random Engineering, Physics, ..., Concepts and Ideas)

A sci-hub search gives many results on this. An example: Reduction of Wind Turbine Noise using Optimized Airfoils and Trailing-Edge Serrations

A similar topic: Biomimicry: airfoils inspired by humpback whales, seals, and other animals