THE STYLUS-GROOVE INTERACTION IN PHONOGRAPH PLAYBACK.
HARVARD UNIV CAMBRIDGE MASS ACOUSTICS RESEARCH LAB
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The report deals with the problem of predicting the vibrational motion of a phonograph stylus sliding in a modulated record groove. This contact problem is given a new generalized formulation in which the nonlinear deformation properties of the groove are left unspecified. The resulting analysis indicates that these nonlinear properties can be deduced from measurements of two functions that characterize the linear properties of the stylus-groove interaction 1 the mechanical impedance of an unmodulated groove and 2 a scanning function that arises on account of the finite area of contact at each groove wall. We estimate the scanning function from available scanning-loss data by developing a phenomenological scanning theory. The groove impedance, in contrast, had to be measured directly our experimental method is new and can be used to measure the impedance presented by any surface to a vibrating indenter. Several of our theoretical conclusions regarding total playback distortion are verified by data in the literature, and in no case does it appear that our conclusions are contradicted by the available data. Author
- Recording and Playback Devices