Small UAS (unmanned aerial systems) are used for research across many disciplines to monitor the environment or to access isolated areas. These vehicles can produce significant aerodynamically-generated noise which has been shown to negatively influence the surrounding environment. Our present research focuses on the noise produced by small propeller-driven UAS and noise prediction tools for quiet design. We are interested in the noise produced by low-Reynolds number propellers, multi-rotor interaction as well as maneuvering and turbulence ingestion. Results are used to develop noise mitigation techniques and assess applicable bio-inspired designs.