Method and apparatus for active reduction of speakerphone singing
AssigneeAT&T Corp.
InventorsRichard Henry Erving, Robert Raymond Miller II
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Abstract
In a speakerphone device identification of signals (i.e., voice input or speaker output) in a process for reducing acoustic feedback, in a communication device, is accomplished by adding a signature noise (i.e., an identification mark) to output signals radiated by the speaker to enable these signals to be separated from speech input to the microphone. Having identified the signal (i.e., speech output) likely to cause a “singing” phenomenon, appropriate insertion loss to reduce the feedback may be added to the appropriate speech path within the communication device, to reduce a probability of singing.
Claims15
In a communication device having a speech input device and a voice output device in proximity to one another wherein an output from the voice output device may be feedback to the speech input device, a method of applying loss insertion into the communication device to prevent feedback oscillations/acoustic instability between the speech input device and the voice output device, comprising the steps of:
- applying an identification mark to output from the voice output device;
- introducing insertion loss in the inactive path of the speech input device and voice output device based on their relative signal levels in order to reduce the feedback oscillations.
A method of differentiating between two signals in an environment capable of producing interactive feedback oscillations and having similar characteristics, comprising the steps of:
- associating an identification mark with one of the signals;
- correlating the two signals to determine the level of combining of the two signals;
- and
- identifying the signal having the identification mark.
A speakerphone connected to a communication network, comprising:
- a loudspeaker for providing voice output connected to an output path having envelope detection;
- a microphone for accepting voice input connected to an input path having envelope detection:
- a PN sequence generator connected to modulate a voice output signal with the PN sequence;
- a correlator connected to both input and output paths to detect PN correlation between signals in the input and output path;
- and
- a loss control processor to insert loss in one of the paths to prevent signal feedback between the input and output path and responsive to envelope detection in the paths and the correlator.
Dependencies are inferred from the claim text.