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Frequency modulation of a sound signal produces some very interesting and sometimes not readily identifiable auditory sensations. Distortion of this type is caused in sound records by the nonuniform speed of the record during the recording or reproducing process.While the physical nature of frequency modulation and some of the physiological effects produced by it are discussed, the paper consists largely of demonstrations including a demonstration of the side‐band nature of flutter, the influence of room acoustics on the perception of flutter, the auditory effects of flutter in single frequency tones, and a demonstration of the auditory effects of frequency modulation in speech and music.