A new application of adaptive filters for restoration of archived gramophone recordings

The authors present a method for restoration of archived gramophone recordings for the case in which more than one copy of a record is available. Often, played-back signals are not in synchronism. Synchronization of two sampled waveforms usually requires that one of the signals be interpolated. An adaptive FIR (finite-impulse response) interpolator based on the least-square error criterion is used to synchronize the signals. Analysis of the interpolator shows that in addition to interpolation significant noise rejection is achieved at its output. Since least-squares filters are sensitive to outliers it is necessary to filter out relatively large impulsive disturbances prior to adaptive filtering. The authors present a detection-estimation algorithm for impulsive noise removal