Distortion in the Reproduction of Hill-and-Dale Recording

In the reproduction of a hill-and-dale recording, the curve traced by the reproducer stylus differs from the recorded curve, with the consequent introduction of both frequency and amplitude distortion. This distortion is here called “tracing distortion,” and must be tolerated only in virtue of the physical necessity of a finite tip radius for the reproducer stylus. A description is given of the results obtained in a study of this phenomenon, together with curves and formulas for the quantitative determination of the magnitude of both the amplitude distortion (i. e., harmonic generation) and the frequency distortion (i. e., decay in fundamental), as functions of the amplitude and frequency of the recorded undulation, the linear groove speed, and the tip radius of the reproducer stylus. — Among other conclusions reached, it is shown that the maintenance of the minimum radius of curvature of the recorded undulations at least equal to or larger than the tip radius of the reproducer stylus is an extremely inaccurate criterion of good-quality reproduction. For “constant-velocity” recordings, less than 10 per cent rms. harmonic generation is obtained when the minimum radius of curvature of the recorded undulation is greater than 5 times the tip radius of the reproducer stylus. Moreover, the generation of harmonics due to tracing distortion is a much more serious limitation upon the quality of the reproduction than is the loss or attenuation of fundamental frequency, as, for example, in cases where the loss of fundamental is only 2 db., the harmonic generation is prohibitively high, being much greater than 10 per cent. — The Introduction and Section I give a physical account of the phenomenon of tracing distortion and deal with all the data necessary for a practical application of the formulas derived in Section II.

Print ISSN

0097-5834

Published

1937-11

Content type

Original Research

DOI

10.5594/J14730