Patent US 4,076,969

This invention describes a system and method for detecting unwanted pop and click sound signals caused by mechanical defects on a recording medium. A pair of wholly or partially correlated signals is generated from the recorded sound information by a conventional stereo pickup device. The output signals of the stereo pickup device are combined so that desired sound signals generated by horizontal movement on the record medium are subtracted and undesired signals generated by vertical movement on the record medium are added. The resulting undesired signal representing clicks and pops is detected as the noise signal. A gating signal starting before the leading edge of the detected undesired sound signal terminating innocuously on the sound signal, and having a width that is greater than the width of the detected undesired sound signal, is used in the system to eliminate the undesired signals.