Blind equalization in the cepstral domain for robust telephone based speech recognition

An adaptive filter in a blind equalization scheme has recently been proposed to reduce telephone line effects for speech recognizers. The implementation of the blind equalization scheme using a circular-convolution frequency domain adaptive filter has been described in a previous paper. This paper presents a new implementation of this blind equalization scheme in the cepstral domain. The property of a constant long-term cepstrum of speech helps to compute the gradient used for adapting the weights. The performances of the spectral domain and the cepstral domain implementations are then compared. These filters prove to be efficient for the channel equalization task. Furthermore, speech recognition experiments show that the cepstral domain on-line adaptive filter outperforms the cepstral trajectories high-pass filter (on-line approach). This technique offers almost the same performance as the conventional cepstral substraction technique (off-line approach).