Removal of swirl artifacts from celp based speech coders

Abstract From the Canadian patent

The perception of speech processed by a CELP based coder such, as a VSELP coder, when operating in noisy background conditions is improved by removing swirl artifacts during silence periods. This is done by removing the low frequency components of the input signal when no speech is detected. A speech activity detector distinguishes between a periodic signal, like speech and a non-periodic signal, like, noise by using most of the VSELP coder internal parameters to determine the speech or non-speech conditions. To prevent the VSELP coder from determining pitches for non-periodic signals a high pass, filter is applied to the input signal to remove the pitch information for which the VSELP …