Fan Noise Reduction: An Overview

Fan noise reduction technologies developed as part of the Advanced Subsonic Technology Program are reviewed. Developments in low-noise fan stage design, swept and leaned outlet guide vanes, active noise control, fan wake management, and scarf inlets are discussed. In each case, a description of the technology is presented and, where available, representative results and general conclusions are discussed. The review concludes with a summary of the accomplishments of the AST-sponsored fan noise reduction research and a few thoughts on future work.