回波消除器的研究
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摘要
随着语音通信技术的发展，人们对语音通信质量的要求越来越高。回波消除技术能有效地解决长距离电话网络、IP电话、免提电话和视频会议等通信系统中的回波问题，明显地改善语音通信质量，具有广阔的市场前景。
本论文主要研究自适应回波消除器，包括电回波消除器和声回波消除器两个方面。自适应回波消除器可以生成一个模拟的回波信号。从近端信号中减掉该模拟回波信号，就可以实现回波消除。
本文是按以下几方面组织的：
第一章简要介绍了回波消除器的背景知识，包括回波产生机理，自适应回波消除器的基本原理和基本构成模块，最后介绍了本文的主要工作。
第二章主要讨论了各种自适应滤波算法。根据实际通信系统的要求，主要研究了减小自适应算法的计算复杂度，以便进行实时处理，降低系统成本。还探讨了各种自适应滤波算法之间的联系和区别。
第三章介绍了子带技术和子带自适应滤波器，着重讨论了子带自适应滤波技术的好处和子带混叠对回波消除器的影响。
第四章结合回波消除器的实现，研究了加快收敛的实用方法和减少回波消除器计算量的措施。提出了一种新的基于双辅助滤波器结构的回波消除器，讨论了有限精度的影响和用TITMS320C549DSP实现的有关问题。
第五章和第六章给出了电回波消除器和声回波消除器的测试结果以及未来工作展望。其中主要测试指标为稳态残留回波和收敛速度。
The echo problem exists in many fields, such as large loop delay telecommunication channels, mobile phone system and teleconference system etc. It's difficult to get smooth conversation without proper echo control. So to support high-speech-quality voice communication, the technology of echo cancellation has been a very active research field in the recent years.
This paper is focused on the adaptive echo canceller, which includes the electric echo canceller and the acoustic echo canceller. The basic principle of the adaptive echo canceller can be summarized as follows:
Adaptively synthesize a replica of the echo and subtract it from the echo-corrupted signal.
This paper is organized as follows:
The background knowledge about the echo canceller such as echo mechanism, the basic principle and basic components is introduced in the first chapter.
In the second chapter, many kinds of adaptive filter algorithms are discussed. To meet the requirement of the real-time processing, we put more emphasis on the fast algorithms and the algorithms that can get a tradeoff between the convergence performance and the compute complexity. The correlation and the difference of these algorithms are also discussed.
The subband technology and the subband adaptive filters are introduced in the third chapter. We especially focus on the merit of the subband adaptive filter technology and the influence to the performance of the echo canceller because of the subband alias.
Then according to the implementation of the echo canceller, we discuss the applied methods to improve the convergence speed and reduce the computation complexity. A new kind of echo canceller based on the structure of dual-assistant filters is proposed to solve the double talk detection problem. Other implementation issues such as finite precision effects and the realization based on TI TMS320C549 are also discussed.
Finally, the test results are given to demonstrate the performance of the design electric echo canceller and acoustic echo canceller, where the steady residual echo and the rate of convergence are the main indexes.
本论文主要研究自适应回波消除器，包括电回波消除器和声回波消除器两个方面。自适应回波消除器可以生成一个模拟的回波信号。从近端信号中减掉该模拟回波信号，就可以实现回波消除。
本文是按以下几方面组织的：
第一章简要介绍了回波消除器的背景知识，包括回波产生机理，自适应回波消除器的基本原理和基本构成模块，最后介绍了本文的主要工作。
第二章主要讨论了各种自适应滤波算法。根据实际通信系统的要求，主要研究了减小自适应算法的计算复杂度，以便进行实时处理，降低系统成本。还探讨了各种自适应滤波算法之间的联系和区别。
第三章介绍了子带技术和子带自适应滤波器，着重讨论了子带自适应滤波技术的好处和子带混叠对回波消除器的影响。
第四章结合回波消除器的实现，研究了加快收敛的实用方法和减少回波消除器计算量的措施。提出了一种新的基于双辅助滤波器结构的回波消除器，讨论了有限精度的影响和用TITMS320C549DSP实现的有关问题。
第五章和第六章给出了电回波消除器和声回波消除器的测试结果以及未来工作展望。其中主要测试指标为稳态残留回波和收敛速度。
The echo problem exists in many fields, such as large loop delay telecommunication channels, mobile phone system and teleconference system etc. It's difficult to get smooth conversation without proper echo control. So to support high-speech-quality voice communication, the technology of echo cancellation has been a very active research field in the recent years.
This paper is focused on the adaptive echo canceller, which includes the electric echo canceller and the acoustic echo canceller. The basic principle of the adaptive echo canceller can be summarized as follows:
Adaptively synthesize a replica of the echo and subtract it from the echo-corrupted signal.
This paper is organized as follows:
The background knowledge about the echo canceller such as echo mechanism, the basic principle and basic components is introduced in the first chapter.
In the second chapter, many kinds of adaptive filter algorithms are discussed. To meet the requirement of the real-time processing, we put more emphasis on the fast algorithms and the algorithms that can get a tradeoff between the convergence performance and the compute complexity. The correlation and the difference of these algorithms are also discussed.
The subband technology and the subband adaptive filters are introduced in the third chapter. We especially focus on the merit of the subband adaptive filter technology and the influence to the performance of the echo canceller because of the subband alias.
Then according to the implementation of the echo canceller, we discuss the applied methods to improve the convergence speed and reduce the computation complexity. A new kind of echo canceller based on the structure of dual-assistant filters is proposed to solve the double talk detection problem. Other implementation issues such as finite precision effects and the realization based on TI TMS320C549 are also discussed.
Finally, the test results are given to demonstrate the performance of the design electric echo canceller and acoustic echo canceller, where the steady residual echo and the rate of convergence are the main indexes.
引文
[1] D. L. Duttweiler, Y. S. Chen. A Single-Chip VLSI Echo Canceller. BSTJ, 1980, Vol. 59(2): 149-160
[2] ITU-T Recommendation G.164, Echo suppressors, 1988
[3] 覃景繁，韦岗，欧阳景正．回波消除理论进展及其应用，电路与系统学报，1998，Vol．3(3)：73-80
[4] 殷福亮，刘恩彩等．回波抵消器研制报告．1997
[5] 殷福亮，宋爱军，数字信号处理C语言程序集．沈阳：辽宁科学技术出版社，1997
[6] [美]B．维德罗，S．D，史蒂诶斯著，王永德，龙宪惠译．自适应信号处理．成都：四川大学出版社，1991
[7] B. Widrow, S. D. Stearns. Adaptive Signal Processing. N. J., Prentice-Hall, Englewood Cliffs, 1985.
[8] S. Haykin. Adaptive Filter Theory. Fourth Edition. 北就：电子工业出版社，2002
[9] ITU-T Recommendation G.167, Acoustic Echo Controllers, 1993
[10] ITU-T Recommendation G.168, Echo Cancellers, 2000
[11] 王宏禹．随机数字信号处理．北京：科学出版社，1988
[12] 何振亚．自适应信号处理．北京：科学出版社，2002
[13] 王宏禹，邱天爽．自适应噪声抵消与时间延迟估计．大连：大连理工大学出版社，1999
[14] S. Narayan, A. M. Peterson, M. J. Narasimha. Transform domain LMS algorithm. IEEE Trans. on Acoustics, Speech and Signal Processing, 1983, Vol. 31 (6): 609-615
[15] D. T. M. Slock. On the convergence behavior of the LMS and the normalized LMS algorithm. IEEE Transactions on Signal Processing, 1993, Vol. 41(9): 2811-2825
[16] J. M. Cioffi, T. Kailath. Fast recursive least squares transversal filters for adaptive filtering. IEEE Trans on Acoustics, Speech and Signal Processing, 1984, Vol. 32(2): 304-337
[17] Thierry Petillon, Andre Gilloire Sergios Theodoridis. Complexity reduction in fast RLS transversal adaptive filters with application to acoustic echo cancellation. Proceedings of IEEE ICASSP, 1992. Vol. 4:37-40
[18] J. Botto, G. V. Moustakides. Stabilizing the fast-Kalman algorithms. IEEE Trans on Acoustics, Speech and Signal Processing, 1989, Vol. 37(9): 1342-1348
[19] D. T. M. Slock, T. Kailath. Numerically stable fast transversal filters for recursive least squares adaptive filtering. IEEE Trans. on Signal Processing, 1991, Vol. 39(1): 92-114
[20] A. Benallal, A. Gillorie. Improvement of the tracking ability of the numerically stable fast RLS algorithms for adaptive filtering. Proceedings of IEEE ICASSP, 1989. 1031-1034
[21] J. Benesty, P. Duhamel. A set of algorithms linking NLMS and block RLS algorithms. IEEE Trans. on Signal Processing, 1999, Vol, 43(2): 444-453
[22] S. Gay, S. Tavathia. The fast affine projection algorithm. Proceedings of IEEE ICASSP, 1995. 3023-3027
[23] M. Tanaka, S. Makino, J. Kojima. A block exact fast affine projection algorithm. IEEE Trans. on Speech and Audio Processing, 1999, Vol. 7(1): 79-87
[24] G. Moustakides, S. Thodoridis. Fast Newton transversal algorithms-A new class of adaptive estimation algorithms. IEEE Trans. on Signal Processing, 1991, Vol. 39(10): 2184-2193
[25] Thierry Petillon, Andre Gilloire, Sergios Theodoridis. The fast Newton transversal filter: an efficient scheme for acoustic echo cancellation in mobile radio. IEEE Trans. on Signal Processing, 1994, Vol. 42(3): 509-517
[26] B. Farhang-Boroujeny. Fast LMS/Newton algorithms based on autoregressive modeling and their application to acoustic echo cancellation. IEEE Trans. on Signal Processing, 1997, Vol. 45(8): 1987-2000
[27] 王永德，王春霞．一种改进的快速LMS／Newton算法及其在声回波对消中的应用．电子学报，2000，Vol．28(2)：97-100
[28] G. Clark, S. Mitra, S. Parker. Block implementation of adaptive digital filters. IEEE Trans. on Circuits and System, 1981, Vol.26 (6): 584-592
[29] W. Mikhacl, F. Wu. Fast algorithms for block FIR adaptive digital filtering. IEEE Trans. on Circuits and System, 1987, Vol. 34(10): 1152-1160
[30] J. Benesty, P. Duhamel. A fast exact least mean square adaptive algorithm. IEEE Trans. on Signal Processing, 1992, Vol. 40(12): 2904-2920
[31] K. Berberidis, S. Theodoridis. A new fast block adaptive algorithm. IEEE Trans. on Signal Processing, 1999, Vol. 47(1): 75-87
[32] K. Maouche, D. T. M. Slock. Fast subsampled-updating stabilized fast transversal filter (FSU SFTF) RLS algorithm for adaptive filtering. IEEE Trans. on Signal Processing, 2000, Vol. 48(8): 2248-2257
[33] J. D. Johnston. A filter family designed for use in quadrature mirror filter banks. Proceeding of IEEE ICASSP, 1980. 291-294
[34] R. E. Crochiere, L. R. Rabiner. Multirate Digital Signal Processing. Prentice-Hall, 1983
[35] 宗孔德．多抽样率信号处理．北京：清华大学出版社，1996
[36] 杨福生．小波变换的工程分析与应用．北京：科学出版社，2000
[37] Koilpillai R. D., Vaidyanathan P. P. Cosine-modulated FIR filter banks satisfying perfect reconstruction. IEEE Trans. on Signal Processing, 1992, Vol. 40(4): 770-783.
[38] A. GiIloire, M. Vetterli. Adaptive filtering in subbands with critical sampling: analysis, experiments, and application to acoustic echo cancellation. IEEE Trans. on Signal Processing, 1992, Vol. 40(8): 1862-1875
[39] A. Gilloire, M. Vetterli. Adaptive FIR filter structure based on the generalized subband decomposition of FIR filters. IEEE Trans. Circuits and systems, 1993, Vol. 40(2): 354-362
[40] B. Farhang-Boroujeny, Z. Wang. Adaptive filtering in subbands: Design issues and
experimental results for acoustic echo cancellation. Signal Processing, 1997, Vol. 61: 213-223
[41] 陈品，王宏禹，邱天爽．基于输入信号白化的新LMS算法．大连理工大学博士生学术动态，2002．106-109
[42] D. L. Duttweiler. Proportionate normalized least-mean-squares adaptation in echo cancellers. IEEE Trans. on Speech and Audio Processing, 2000, Vol. 8(5): 508-518
[43] T. Gansler, J. Benesty, S. L. Gay, M. M. Sondhi. A robust proportionate affine projection algorithm for network echo cancellation. Proceedings of IEEE ICASSP, 2000. Vol. 2: 793-796
[44] S. L. Gay. An efficient, fast converging adaptive filter for network echo cancellation. Conference Record of the Thirty-Second Asilomar Conference on Signals, Systems & Computers, 1998. Vol. 1:394-398
[45] P. C. -W. Yip, D. M. Etter. An adaptive multiple echo canceller for slowly time-varying echo paths. IEEE Trans. on Communications, 1990, Vol. 38(10): 1693-1698
[46] D. Duttweiler. Subsampling to estimate delay with application to echo canceling. IEEE Trans. on Acoustics, Speech and Signal Processing, 1983, Vol. 31(5): 1090-1099
[47] A. Sugiyama, H. Sato, A. Hirano, S. Ikeda. A fast convergence algorithm for adaptive FIR filters under computational constraint for adaptive tap-position control. IEEE Trans. on Circuits and Systems Ⅱ: Analog and Digital Signal Processing, 1996, Vol. 43(9): 629-636
[48] Andreas Mader, Henning Puder, Gerhard Uwe Schmidt. Step-size control for acoustic echo cancellation filters-an overview. Signal Processing, 2000, Vol. 80(9): 1697-1719
[49] Eberhard, Hnsler, Gerhard Uwe Schmidt. Hands-free telephones-joint control of echo cancellation and postfiltering. Signal Processing, 2000, Vol. 80(11): 2295-2305
[50] J. H. Cho, D. R. Morgan, J. Benesty. An objective technique for evaluating doubletalk detectors in acoustic echo cancellers. IEEE Trans. on Speech and Audio Processing, 1999, Vol. 7(6): 718-724
[51] D. L. Duttweiler. A twelve-channel digital echo canceller. IEEE Trans. on Communications, 1978, Vol. 26(5): 647-653
[52] Jacob Benesty. Dennis R. Morgan, Jun H. Cho. A new class of doubletalk detectors based on cross-correlation. IEEE Trans. on Speech and audio processing, 2000, Vol. 8(2): 168-172
[53] J. Benesty, D. R. Morgan, J. H. Cho. A Family of Doubletalk Detectors Based on Cross-Correlation. International Workshop on Acoustic Echo and Noise Control. Pocona Manor, Pennsylvania, USA, 1999. 108-111
[54] T. Gansler, M. Hansson, C. -J. Ivarsson, G. Salomonsson. A double-talk detector based on coherence. IEEE Trans. on Communications, 1996, Vol. 44(11): 1421-1427
[55] H. Ye and B. X. Wu. A new double-talk detection algorithm based on the orthogonality theorem. IEEE Trans. on Communications, 1991, Vol. 39(11): 1542-1545
[56] K. Ochiai, et al. Echo canceller with two echo path models. IEEE Trans. on Commu-
nications, 1977, Vol. 25(6): 589-595
[57] Jianfeng Liu, A novel adaptation scheme in the NLMS algorithm for echo cancellation. IEEE Signal Processing Letters, 2001, Vol. 8(1): 20-22
[58] Wang Youhua, Y. Terada, M. Matsui, K. Iida, K. Nakayama. Development of high quality acoustic subband echo canceller using dual-filter structure and fast recursive least squares algorithm. Proceedings of IEEE ICASSP, 2000, Vol. 6:3674-3677
[59] Texas Instruments. TMS320C54x DSP Reference Set, volume 1: CPU and peripherals. 1996
[60] Texas Instruments. TMS320C54x DSP Reference Set, volume 3: Algebraic Instruction Set. 1996
[61] S. Gustafsson, R. Martin, P. Vary. Combined acoustic echo control and noise reduction for hands-free telephony. Signal Processing, 1998, Vol. 64(1): 21-32
[62] S. Gustafsson, R. Martin, P. Jax, P. Vary. A psychoacoustic approach to combined acoustic echo cancellation and noise redaction. IEEE Trans. on Speech and Audio Processing, 2002, Vol. 10(5): 245-256
[2] ITU-T Recommendation G.164, Echo suppressors, 1988
[3] 覃景繁，韦岗，欧阳景正．回波消除理论进展及其应用，电路与系统学报，1998，Vol．3(3)：73-80
[4] 殷福亮，刘恩彩等．回波抵消器研制报告．1997
[5] 殷福亮，宋爱军，数字信号处理C语言程序集．沈阳：辽宁科学技术出版社，1997
[6] [美]B．维德罗，S．D，史蒂诶斯著，王永德，龙宪惠译．自适应信号处理．成都：四川大学出版社，1991
[7] B. Widrow, S. D. Stearns. Adaptive Signal Processing. N. J., Prentice-Hall, Englewood Cliffs, 1985.
[8] S. Haykin. Adaptive Filter Theory. Fourth Edition. 北就：电子工业出版社，2002
[9] ITU-T Recommendation G.167, Acoustic Echo Controllers, 1993
[10] ITU-T Recommendation G.168, Echo Cancellers, 2000
[11] 王宏禹．随机数字信号处理．北京：科学出版社，1988
[12] 何振亚．自适应信号处理．北京：科学出版社，2002
[13] 王宏禹，邱天爽．自适应噪声抵消与时间延迟估计．大连：大连理工大学出版社，1999
[14] S. Narayan, A. M. Peterson, M. J. Narasimha. Transform domain LMS algorithm. IEEE Trans. on Acoustics, Speech and Signal Processing, 1983, Vol. 31 (6): 609-615
[15] D. T. M. Slock. On the convergence behavior of the LMS and the normalized LMS algorithm. IEEE Transactions on Signal Processing, 1993, Vol. 41(9): 2811-2825
[16] J. M. Cioffi, T. Kailath. Fast recursive least squares transversal filters for adaptive filtering. IEEE Trans on Acoustics, Speech and Signal Processing, 1984, Vol. 32(2): 304-337
[17] Thierry Petillon, Andre Gilloire Sergios Theodoridis. Complexity reduction in fast RLS transversal adaptive filters with application to acoustic echo cancellation. Proceedings of IEEE ICASSP, 1992. Vol. 4:37-40
[18] J. Botto, G. V. Moustakides. Stabilizing the fast-Kalman algorithms. IEEE Trans on Acoustics, Speech and Signal Processing, 1989, Vol. 37(9): 1342-1348
[19] D. T. M. Slock, T. Kailath. Numerically stable fast transversal filters for recursive least squares adaptive filtering. IEEE Trans. on Signal Processing, 1991, Vol. 39(1): 92-114
[20] A. Benallal, A. Gillorie. Improvement of the tracking ability of the numerically stable fast RLS algorithms for adaptive filtering. Proceedings of IEEE ICASSP, 1989. 1031-1034
[21] J. Benesty, P. Duhamel. A set of algorithms linking NLMS and block RLS algorithms. IEEE Trans. on Signal Processing, 1999, Vol, 43(2): 444-453
[22] S. Gay, S. Tavathia. The fast affine projection algorithm. Proceedings of IEEE ICASSP, 1995. 3023-3027
[23] M. Tanaka, S. Makino, J. Kojima. A block exact fast affine projection algorithm. IEEE Trans. on Speech and Audio Processing, 1999, Vol. 7(1): 79-87
[24] G. Moustakides, S. Thodoridis. Fast Newton transversal algorithms-A new class of adaptive estimation algorithms. IEEE Trans. on Signal Processing, 1991, Vol. 39(10): 2184-2193
[25] Thierry Petillon, Andre Gilloire, Sergios Theodoridis. The fast Newton transversal filter: an efficient scheme for acoustic echo cancellation in mobile radio. IEEE Trans. on Signal Processing, 1994, Vol. 42(3): 509-517
[26] B. Farhang-Boroujeny. Fast LMS/Newton algorithms based on autoregressive modeling and their application to acoustic echo cancellation. IEEE Trans. on Signal Processing, 1997, Vol. 45(8): 1987-2000
[27] 王永德，王春霞．一种改进的快速LMS／Newton算法及其在声回波对消中的应用．电子学报，2000，Vol．28(2)：97-100
[28] G. Clark, S. Mitra, S. Parker. Block implementation of adaptive digital filters. IEEE Trans. on Circuits and System, 1981, Vol.26 (6): 584-592
[29] W. Mikhacl, F. Wu. Fast algorithms for block FIR adaptive digital filtering. IEEE Trans. on Circuits and System, 1987, Vol. 34(10): 1152-1160
[30] J. Benesty, P. Duhamel. A fast exact least mean square adaptive algorithm. IEEE Trans. on Signal Processing, 1992, Vol. 40(12): 2904-2920
[31] K. Berberidis, S. Theodoridis. A new fast block adaptive algorithm. IEEE Trans. on Signal Processing, 1999, Vol. 47(1): 75-87
[32] K. Maouche, D. T. M. Slock. Fast subsampled-updating stabilized fast transversal filter (FSU SFTF) RLS algorithm for adaptive filtering. IEEE Trans. on Signal Processing, 2000, Vol. 48(8): 2248-2257
[33] J. D. Johnston. A filter family designed for use in quadrature mirror filter banks. Proceeding of IEEE ICASSP, 1980. 291-294
[34] R. E. Crochiere, L. R. Rabiner. Multirate Digital Signal Processing. Prentice-Hall, 1983
[35] 宗孔德．多抽样率信号处理．北京：清华大学出版社，1996
[36] 杨福生．小波变换的工程分析与应用．北京：科学出版社，2000
[37] Koilpillai R. D., Vaidyanathan P. P. Cosine-modulated FIR filter banks satisfying perfect reconstruction. IEEE Trans. on Signal Processing, 1992, Vol. 40(4): 770-783.
[38] A. GiIloire, M. Vetterli. Adaptive filtering in subbands with critical sampling: analysis, experiments, and application to acoustic echo cancellation. IEEE Trans. on Signal Processing, 1992, Vol. 40(8): 1862-1875
[39] A. Gilloire, M. Vetterli. Adaptive FIR filter structure based on the generalized subband decomposition of FIR filters. IEEE Trans. Circuits and systems, 1993, Vol. 40(2): 354-362
[40] B. Farhang-Boroujeny, Z. Wang. Adaptive filtering in subbands: Design issues and
experimental results for acoustic echo cancellation. Signal Processing, 1997, Vol. 61: 213-223
[41] 陈品，王宏禹，邱天爽．基于输入信号白化的新LMS算法．大连理工大学博士生学术动态，2002．106-109
[42] D. L. Duttweiler. Proportionate normalized least-mean-squares adaptation in echo cancellers. IEEE Trans. on Speech and Audio Processing, 2000, Vol. 8(5): 508-518
[43] T. Gansler, J. Benesty, S. L. Gay, M. M. Sondhi. A robust proportionate affine projection algorithm for network echo cancellation. Proceedings of IEEE ICASSP, 2000. Vol. 2: 793-796
[44] S. L. Gay. An efficient, fast converging adaptive filter for network echo cancellation. Conference Record of the Thirty-Second Asilomar Conference on Signals, Systems & Computers, 1998. Vol. 1:394-398
[45] P. C. -W. Yip, D. M. Etter. An adaptive multiple echo canceller for slowly time-varying echo paths. IEEE Trans. on Communications, 1990, Vol. 38(10): 1693-1698
[46] D. Duttweiler. Subsampling to estimate delay with application to echo canceling. IEEE Trans. on Acoustics, Speech and Signal Processing, 1983, Vol. 31(5): 1090-1099
[47] A. Sugiyama, H. Sato, A. Hirano, S. Ikeda. A fast convergence algorithm for adaptive FIR filters under computational constraint for adaptive tap-position control. IEEE Trans. on Circuits and Systems Ⅱ: Analog and Digital Signal Processing, 1996, Vol. 43(9): 629-636
[48] Andreas Mader, Henning Puder, Gerhard Uwe Schmidt. Step-size control for acoustic echo cancellation filters-an overview. Signal Processing, 2000, Vol. 80(9): 1697-1719
[49] Eberhard, Hnsler, Gerhard Uwe Schmidt. Hands-free telephones-joint control of echo cancellation and postfiltering. Signal Processing, 2000, Vol. 80(11): 2295-2305
[50] J. H. Cho, D. R. Morgan, J. Benesty. An objective technique for evaluating doubletalk detectors in acoustic echo cancellers. IEEE Trans. on Speech and Audio Processing, 1999, Vol. 7(6): 718-724
[51] D. L. Duttweiler. A twelve-channel digital echo canceller. IEEE Trans. on Communications, 1978, Vol. 26(5): 647-653
[52] Jacob Benesty. Dennis R. Morgan, Jun H. Cho. A new class of doubletalk detectors based on cross-correlation. IEEE Trans. on Speech and audio processing, 2000, Vol. 8(2): 168-172
[53] J. Benesty, D. R. Morgan, J. H. Cho. A Family of Doubletalk Detectors Based on Cross-Correlation. International Workshop on Acoustic Echo and Noise Control. Pocona Manor, Pennsylvania, USA, 1999. 108-111
[54] T. Gansler, M. Hansson, C. -J. Ivarsson, G. Salomonsson. A double-talk detector based on coherence. IEEE Trans. on Communications, 1996, Vol. 44(11): 1421-1427
[55] H. Ye and B. X. Wu. A new double-talk detection algorithm based on the orthogonality theorem. IEEE Trans. on Communications, 1991, Vol. 39(11): 1542-1545
[56] K. Ochiai, et al. Echo canceller with two echo path models. IEEE Trans. on Commu-
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