Noise reduction and echo cancellation front-end for speech codecs

We present an enhancement front-end for speech codecs, which consists of the integrated elements of noise reduction and echo cancellation. By including these elements, the front-end performs the task of mitigating the objectionable effects of the two major factors, i.e., noise and echo, which adversely affect the quality of most transmission systems, especially when low bit rate codecs are used. The use of this front-end is demonstrated with the 7.4 kbps IS-641 codec (enhanced full-rate standard for IS-136 systems). The integrated speech-processing unit has the advantage of utilizing the synergy among its components: the voice activity detector in the speech codec, the noise reduction, and the echo canceller. This synergy manifests itself both in the form of a reduction of the overall computational complexity by the use of a number of shared elements among the unit's various components, as well as an improved performance resulting from these components working together. The system displays high performance in both clean and noisy environments and it works well with low bit rate codecs.

[1]  Bouquin Jeann.  How to Reduce the Noise Influence in a Joint System Developed for Echo and Noise Cancellation , 1997 .

[2]  George S. Moschytz,et al.  Noise reduction by noise-adaptive spectral magnitude expansion , 1994 .

[3]  S. Thomas Alexander,et al.  Adaptive Signal Processing , 1986, Texts and Monographs in Computer Science.

[4]  Rainer Martin,et al.  Combined acoustic echo control and noise reduction for hands-free telephony — State of the art and perspectives , 1996, 1996 8th European Signal Processing Conference (EUSIPCO 1996).

[5]  K. Swaminathan,et al.  Robust voice activity detection for DTX operation of speech coders , 1999, 1999 IEEE Workshop on Speech Coding Proceedings. Model, Coders, and Error Criteria (Cat. No.99EX351).

[6]  P. Heitkamper,et al.  Optimization of an acoustic echo canceller combined with adaptive gain control , 1995, 1995 International Conference on Acoustics, Speech, and Signal Processing.

[7]  Thomas Burger.  Practical applications of adaptation control for NLMS-algorithms used for echo cancellation with speech signals , 1995 .

[8]  Jacob Benesty,et al.  An objective technique for evaluating doubletalk detectors in acoustic echo cancelers , 1999, IEEE Trans. Speech Audio Process..

[9]  S F Bahgat,et al.  Envelope expansion methods for speech enhancement. , 1991, The Journal of the Acoustical Society of America.

[10]  Kumar Swaminathan,et al.  Integrated noise reduction and echo cancellation for IS-136 systems , 2000, 2000 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings (Cat. No.00CH37100).