US 8,027,486 B1Granted

Probabilistic ringing feedback detector with frequency identification enhancement

AssigneeClearOne Communications, Inc.

InventorsAshutosh Pandey, David Lambert

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Abstract

Disclosed herein are detectors of audio ringing feedback, that is decaying feedback with a gain of less than one, those detectors utilizing a repeated gain measurement that applied to a range of gain values characteristic of ringing-type feedback. Those gain measurements, while in the range, increase a probability measurement of feedback. When the probability of feedback reaches a threshold, a detection of feedback is made and feedback countermeasures, such as the application of a notch filter, may be applied. Optionally, the audio gain around likely frequencies of feedback may be enhanced for a time to increase the resolution of identification of a feedback frequency, which may be identified through an interpolative method. Repeated gain measurements may also identify building-type feedback. A ringing detector may include more than one range of detection, for example for building, strong-ringing and weak-ringing feedback.

Claims24

Dependent claims

An amplified system incorporating a suppressor against ringing feedback, that system further including feedback enhancement to more precisely identify a frequency of feedback, comprising:

a microphone;
a speaker;
an amplifier connected to said microphone and said speaker in a way such that sound received at said microphone is produced at said speaker at an amplified level;
a frequency level detector configured to provide a volume level with respect to a plurality of frequency-spectrum divisions;
a gain determiner configured to compute the gain between two measured volumes of sound at frequencies of potential feedback measured at two contemporaneous times;
a ringing detector functional to evaluate the computed gain at a plurality of frequency divisions, wherein each gain evaluation produces a positive indication of ringing in association with a frequency division where the corresponding computed gain about that frequency division remains substantially within a ringing range for a first preselected period of time;
and
a feedback enhancer functional to provide temporary gain enhancement for an enhancement period of time, the gain enhancement applying a selected level of boost to the amplification of said amplifier wherein decaying-type feedback may become building feedback;
and
an interpolator functional to examine a feedback signal within the frequency range of a frequency bin, said interpolator using the measurements at neighboring bins to achieve a better resolution of the measurement of a the frequency of a feedback signal, said interpolator producing a frequency of feedback during a time of feedback enhancement.

7 more elements

A ringing detection system for the suppression of ringing artifacts in an amplified system, said system include a method of enhancing the accuracy of the measurement of the frequency of ringing-feedback, said system comprising:

a port functional to sample an audio signal;
a frequency level detector receiving a signal of said port, said detector configured to provide a volume level with respect to a plurality of frequency-spectrum divisions;
a gain determiner configured to compute the gain between two measured volumes of sound at frequencies of potential feedback measured at two contemporaneous times;
a ringing detector functional to evaluate the computed gain at a plurality of frequency divisions, wherein each gain evaluation produces a positive indication of ringing in association with a frequency division where the corresponding computed gain about that frequency division remains substantially within a ringing range for a first preselected period of time;
a feedback enhancer functional to provide temporary gain enhancement for an enhancement period of time, the gain enhancement applying a selected level of boost to the amplification of said amplifier wherein decaying-type feedback may become building feedback;
and
an interpolator functional to examine a feedback signal within the frequency range of a frequency bin, said interpolator using the measurements at neighboring bins to achieve a better resolution of the measurement of a the frequency of a feedback signal, said interpolator producing a frequency of feedback during a time of feedback enhancement.

4 more elements

Dependencies are inferred from the claim text.