The recent improvement in disk recording standards is emphasized. The combined cutting and burnishing action of a standard lacquer cutting stylus is explained. It is emphasized that cutting and burnishing take place simultaneously (in terms of wavelength) at low frequencies; but that at higher frequencies the two operations are separated by a discrete wavelength fraction; phase shift and attenuation result. These depend upon circumferential velocity, hence are worst at low rotational speed and small distance from the center of the record. The experimental study, therefore, is confined to 3331r.p.m. recordings at various diameters, and the recorded velocity as a function of frequency and diameter is determined for needles with different lengths of dulling. The effect of amount of dulling on surface noise is determined, and a technique for comparing the perfection of action of cutting and burnishing is given. It is emphasized that for modern quality standards the length of dulling must be restricted and that the resulting increase in surface noise is not of great importance.

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