Band-energy near-end echo reducer for tonal signalling detectors

Details Band-energy near-end echo reducer for tonal signalling detectors Band-energy near-end echo reducer for tonal signalling detectors

1995-03-09

1997-05-20

Zele, Krista M.

Telephonic communications

Echo cancellation or suppression

379399, 379408, 379409, H04M 1100

Patent

active

056319576

ABSTRACT:
Near-end echo-reduction is achieved by passing a transmit signal through a first filter bank and feeding a remote signal plus an echo of the transmit signal through a second filter bank, then subtracting a gain-coefficient-compensated (scaled) version of the filtered transmit signal from the filtered-composite-remote signal to obtain an echo-reduced receive signal. The echo-reduced receive signal is suitably employed by tone decoders, voice response mechanisms, and the like, in a telephone system, and avoids false alarms due to near-end echo. In one embodiment, the gain coefficients are fixed for each frequency of interest. In another embodiment, the gain coefficients are dynamically arrived at based on the filtered transmit signal and the echo-reduced receive signal. The two filter banks can be combined in one, multiplexed filter bank.

REFERENCES:
patent: 4460808 (1984-07-01), Battista et al.
patent: 4609878 (1986-09-01), Rodgers
patent: 5132963 (1992-07-01), Ungerboeck
patent: 5214693 (1993-05-01), Chujo
patent: 5375166 (1994-12-01), Odaohara
patent: 5400394 (1995-03-01), Raman et al.
IEEE International Conference on Acoustic, Speech and Signal Processing, vol. 4, Mar. 1992, pp. 513-516, V. Raman, M Cromack, "Fast Echo Cancellation in a Voice-processing System".
Fast Echo Cancellation in a Voice-Processing System (Vijay R. Raman et al) IEEE Sep. 1992 (pp. IV-513-IV516).

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