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The extraction of spectral density and correlation functions from vibration and acoustic signals, etc., has been undergoing a continuing process of refinement. This refinement has been brought about by more and more stringent analysis requirements. The design of improved analyzers to meet such requirements has been going on concurrently. Usually the signals to be analyzed are played back from magnetic tape recorders. The flutter of the tape transports involved can degrade or effectively destroy such possible desired parameters as high resolution, high dynamic range, extreme accuracy of analysis, etc., for either spectral density or correlation function plots. Formulae are developed to show how both sinusoidal and random components of flutter introduce error into the analysis, and to indicate how flutter limits the range of useable values of spectral resolution, correlation time-delay, etc. The pertinent features of a tape transport, the influential characteristics of its flutter, etc., are also discussed. Suggestions are also given regarding the interpretation of the data on transport flutter that is usually available.