Multiple tone detection using out-of-band background detector

Details Multiple tone detection using out-of-band background detector Multiple tone detection using out-of-band background detector

1997-08-06

2000-10-03

Kuntz, Curtis A.

Telephonic communications

Diagnostic testing, malfunction indication, or electrical...

Testing of subscriber loop or terminal

379 6, 379 24, 379386, 379283, H04M 124, H04M 100

Patent

active

061283703

ABSTRACT:
A multiple tone detector includes n tone detectors, each detecting one of n distinct tones, where n.gtoreq.2, and a background detector which generates a measure of accumulative background energy E.sub.avg in a frequency band or bands which do not include at least a subset of the n tones. The output of the background detector is applied to a smoothing filter, which generates the accumulative background energy measure E.sub.avg for a current frame as a weighted sum of the background detector output for the current frame and the background energy measure E.sub.avg from a previous frame. A parameter controlling response time of the smoothing filter is varied depending upon whether or not speech is determined to be present in the background portion of the input signal. A processor uses the energy measures from the n tone detectors and the background detector to compute n ratios, where a given ratio is the ratio of the energy measure of the ith tone to the accumulative background energy measure E.sub.avg. The processor determines if each of the n ratios are greater than a threshold, and if the maximum of the n ratios is less than a constant times the minimum of the n ratios, in order to generate a decision as to whether the n tones are present in the input signal.

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