On the Flutter of Motion Picture Projectors and its Measurement

Watanabe Yuzuru

doi:10.11499/sicejl1951.4.492

One of the distortions encountered in sound equipments, such as motion picture projectors, magnetic recorders and phonographs, is that produced by the irregular motion of revolutional mechanisms. It is termed "flutter", and it relates to any deviation of frequency that results from irregular motion in the recording or reproduction of a constant-frequency tone. When we discuss about it, flutter rate must be considered together. Flutter rate is the number of excursions of frequency per second in a-tone which has flutter, each excurision being a complete cycle of deviation. If these deviations are of low frequency they are often referred to colloquially as wow. The flutter is periodically repeated phenomenon, however, the actual flutter is thought to be rather a continual succession of transient phenomenon, and each crest value of deviation from a constant frequency tone is not necessarily the same. For this reason, as a method of calibration, we devised to compound flutter artificially under the condition of a certain quality and quantity utilizing an R.C. audio frequency oscillator. Through the experiment, we have studied the properties of different rate of flutter and different amount of flutter to be indicated in what way on the meter scale. Moreover, a few problems concerning to flutter will be related.

On the Flutter of Motion Picture Projectors and its Measurement

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