Methods of Calibrating Frequency Records

A frequency record cut in lacquer, while an FM calibrator was used to measure the amplitude of motion of the cutting stylus, was processed and calibrated by the following means: a "static" method in which the amplitude of the recorded groove was measured by means of a displacement sensitive gauge; a variable speed method in which the velocity was measured with a pickup while the same reproduced frequency was maintained by rotating the disk at different turntable speeds; the reflected-light-pattern method commonly used in evaluating the recorded velocity; and by direct measurement of the recorded amplitude as pictured in photomicrographs