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This paper summarizes the Company's research and development activity in studies of compressor noise and means for its reduction. Correlation between theory, small-scale-rig tests, and full-scale-engine data are discussed. Special rig and instrumentation systems helpful for diagnosis of compressor noise are described, and illustrations are given of several techniques for reducing noise and the extent to which these techniques worked in rigs and engines. The paper concludes with a discussion of the noise characteristics of possible future high bypass ratio turbofan engines.