A system for reducing impulsive noise on gramophone reproduction equipment

The paper describes a system for detecting and attenuating impulsive noise on gramophone records. Fast transitions and short duration are shown to be the essential characteristics of the impulsive noise waveform and a detector which uses these characteristics to distinguish between the noise and the recorded signal is described. Several methods of producing a noise-free approximation to the recorded signal are discussed and compared. A simple attenuation technique is shown to be as subjectively acceptable as more complex techniques. The designs of delay line and attenuator for optimum performance are considered and the subjective performance of the system is assessed.