Aerodynamic noise is a fundamental concern facing the aviation industry, whether it's the noise generated by a passenger aeroplane, or by a delivery drone. The key feature linking all aerodynamic designs is aerofoils/blades, and these generate both leading- and trailing-edge noise through interaction with unsteady fluid flows. This talk will first discuss the basics of noise generation by aerofoils in unsteady subsonic flows followed by discussing new bio-inspired adapted blade designs for reducing leading-edge noise. It is important for any new design that we understand how it interacts with the flow to reduce noise so that the optimal design can be used in a variety of flow regimes. This talk will therefore present mathematical models that are capable of quickly predicting the generated noise and can be used to infer the noise-reduction mechanisms of blade adaptations.