Evaluation of Fan Noise Using Phase Modulation and Psychoacoustic Theories

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The Ohio State University

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Fans generate complex noise signatures related to their frequency of rotation. In order to reduce noise and improve sound quality, engineers use a variety of methods to reduce or re-distribute the sidebands which appear in the frequency spectrum. One method, phase modulation has already been utilized on air cooled engine fans. The fans were tested with subjective listeners to improve the sound quality of the design. Prior results indicated that there was some correlation between the listeners’ preference and the different levels of modulation. Our research on the human response shows, however, that increased phase modulation may not improve the sound quality as previously claimed. Such results may have direct applications to fan design and similar implications for designing gears, tires, and other rotating mechanical systems.



Phase modulation, Psychoacoustics Subjective