The noise emission of wind turbines and farms can be an important and limiting factor for future cost reductions and growth of wind energy. Closing scientific and technological gaps on wind turbine noise is thus directly supporting the further development of renewable energy while reducing adverse reactions toward wind farms. The present article is providing guidance on the most relevant research directions from an engineering perspective, namely: simulation methods, wind tunnel testing, and wind turbine design. Each topic is addressed separately and specific scientific challenges are identified. Future research directions that may improve our physical understanding of wind turbine noise, as well as facilitate the deployment of wind energy, are outlined. It is concluded that future scientific research on the topic of wind turbine noise should be conducted in a multidisciplinary context to maximize its impact. The suggested topics shall be seen as a collection of what is seen as the most relevant topics across research and product development but shall not be seen as exclusive or interlinked with specific development plans.