Abstract

An active acoustic attenuation system is provided that actively models direct and feedback paths as well as characteristics of the secondary cancelling sound source and the error path on an on-line basis. The primary model uses a recursive least mean squares RLMS algorithm that is excited by the input acoustic noise and uses the residual acoustic noise as an error signal. The secondary sound source or cancelling speaker and the error path are modeled by a second algorithm, particularly an LMS algorithm, that uses an additional auxiliary low level, random, uncorrelated noise source as an input signal. The resulting overall system provides excellent attenuation of narrow band and broad band noise over a relatively wide frequency range on a completely adaptive basis without directional transducers.

Other References

• "Active Noise Reduction Systems in Ducts", J. Tichy, G. E. Warnaka and L. A. Poole, ASME Journal, Nov. 1984, pp. 1-7, FIG. 7
• "Historical Review and Recent Development of Active Attenuators", H. G. Leventhall, Acoustical Society of America, 104th Meeting, Orlando, Nov. 1982, FIG. 8
• "Active Adaptive Sound Control in a Duct: A Computer Simulation", J. C. Burgess, Journal of Acoustic Society of America, 70(3), Sep. 1981, pp. 715-726
• "The Implementation of Digital Filters Using a Modified Widrow-Hoff Algorithm for the Adaptive Cancellation of Acoustic Noise", L. A. Poole, G. E. Warnaka and R. C. Cutter, 1984, IEEE, CH 1945-5/84/0000-0233, pp. 21.7.1-21.7.4, 1984
• "VLSI Systems Designed for Digital Signal Processing", Bowen and Brown, vol. 1, Prentice Hall, Englewood Cliffs, N.J., 1982, pp. 80-87
• "Comments on `An Adaptive Recursive LMS Filter`", Widrow et al, Proceedings of the IEEE, vol. 65, No. 9, Sep. 1977, pp. 1402-1404, FIG. 2
• I.S.V.R. Technical Report No. 127, Elliot and Nelson, Southampton University, England, published in U.S. Department of Commerce; National Technical Information Service, Bulletin No. PB85-189777, Apr. 1984, pp. 1-61
• "An Analysis of Multiple Correlation Cancellation Loops With a Filter in the Auxiliary Path", Morgan, IEEE Transactions Acoustics Speech, Signal Processing, vol. ASSP-28, No. 4, 1980, pp. 454-467
• "Echo Cancellation Algorithms", Gritton and Lin, IEEE ASSP Magazine, Apr. 1984, pp. 30-38
• "Aspects of Network and System Theory", Widrow, Adaptive Filters, edited by R. E. Kalman and N. DeClaris, Holt, Reinhart and Winston, New York, 1971, pp. 563-587
• "Adaptive Control by Inverse Modeling", Widrow et al, Proceedings of 12th Asilomar Conference on Circuits, Systems and Computers, Pacific Grove, Calif., Nov. 6-8, 1978, pp. 90-94
• Adaptive Signal Processing, Widrow and Stearns, Englewood Cliffs, N.J., Prentice-Hall, Inc., 1985, pp. 196, 197, 222, 223
• Number Theory in Science and Communications, M. R. Schroeder, Berlin: Springer-Verlag, 1984, pp. 252-261
• "Adaptive Filters: Structures, Algorithms, and Applications", M. L. Honig and D. G. Messerschmitt, The Kluwer International Series in Engineering and Computer Science, VLSI, Computer Architecture and Digital Signal Processing, 1984