Active acoustic attenuation system for higher order mode non-uni

Details Active acoustic attenuation system for higher order mode non-uni Active acoustic attenuation system for higher order mode non-uni

1988-03-16

1989-03-21

Chin, Tommy P.

Electrical audio signal processing systems and devices

Acoustical noise or sound cancellation

Adjacent ear

381 94, H04B 1500, H04R 128

Patent

active

048151394

ABSTRACT:
A system is provided for increasing the frequency range of an active acoustic attenuation system in a duct without increasing cut-off frequency f.sub.c of the duct or otherwise splitting or partitioning the duct into separate ducts or chambers. The frequency range is increased above f.sub.c to include higher order modes. A plurality of cancelling model sets are provided. Each transverse portion of the acoustic pressure wave has its own set of an adaptive filter model, cancelling speaker, and error microphone. A single input microphone may service all sets.

REFERENCES:
patent: 4473906 (1984-09-01), Warnaka
patent: 4665549 (1987-05-01), Eriksson et al.
patent: 4677676 (1987-06-01), Eriksson
patent: 4677677 (1987-06-01), Eriksson
patent: 4683590 (1987-07-01), Miyoshi
patent: 4736431 (1988-04-01), Allie
L. J. Eriksson, "Higher Order Mode Effects in Circular Ducts and Expansion Chambers", J. Acoust. Soc. Am., 68(2), Aug. 1980, pp. 545-550.
S. J. Elliott, I. M. Stothers and P. A. Nelson, "A Multiple Error LMS Algorithm and Its Application to the Active Control of Sound and Vibration", IEEE Trans. on Acoustics, Speech and Signal Processing, vol. ASSP-35, No. 10, Oct. 1987, pp. 1423-1434.
J. C. Burgess, Journal of Acoustic Society of America, 70(3), Sep. 1981, pp. 715-726.
M. P. Schroeder, "Number Theory in Science and Communications", Berlin: Springer-Verlag, 1984, pp. 252-261.

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