Removing preechoes from audio recordings

A method is described for the attenuation of preecho in audio recordings. Preechoes are attenuated replicas of the future signal that can usually be heard in tape or phonograph recordings in silences or near-silences preceding sudden, high amplitude sounds. The method described is based on a very simple attenuation+delay preecho model. The delay is estimated by use of a modified cross-correlation technique, and the value of the attenuation is obtained by a least-squares estimation. The restoration is carried out in the frequency domain by use of a nonlinear spectral subtraction technique very similar to standard noise suppression methods.