Adaptive sub-band echo suppressor

Details Adaptive sub-band echo suppressor Adaptive sub-band echo suppressor

1982-10-27

1987-02-17

Rubinson, Gene Z.

Telephonic communications

Echo cancellation or suppression

379395, H04B 320

Patent

active

046441085

ABSTRACT:
The subject suppressor is an improved form of echo suppressor used in conjunction with adaptive sub-band speech coders. The suppressor analyzes and uses N contiguous sub-bands of a sub-band speech coder. The intermediate results calculated during the normal operation of such speech coders may be analyzed in the suppressor to determine predictions for the echo levels of each sub-band and to set break in and break out thresholds. A substantial performance improvement with little increase in complexity over current echo suppressors is achieved. The subject suppressor may also be used with adaptive transform speech coders in which the corner frequency points define the edges of "sub-bands" for purposes of this invention. Sub-bands are defined here as contiguous segments of the frequency-energy spectrum. The sub-bands so defined can be formed or analytically divided by a bank of filters as in normal sub-band coders or they can be identified or analyzed as noted above by the corner points of an adaptive transform coder.

REFERENCES:
patent: Re28919 (1976-07-01), Berkley et al.
patent: 3567873 (1971-03-01), Peroni
patent: 3699271 (1972-10-01), Berkley et al.
patent: 3900708 (1975-08-01), Bendel
patent: 4012603 (1977-03-01), Areski et al.
patent: 4031338 (1977-06-01), Campanella et al.
patent: 4130743 (1978-12-01), Boulanger et al.
patent: 4368360 (1983-01-01), Sato et al.
"Le Suppressor d'echo F4", C. Boulanger, Cables and Transmission, vol. 28, No. 2, Apr. 1974, pp. 168-177.
"Digital Adaptive Echo Suppressor", T Areski et al., International Conference on Communications, vol. 3, Subno. 21, pp. 36-4-36-8, Jun. 14-16, 1976.

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