Abstract: Traditionally, echo cancellation has employed linear adaptive filters to cancel echoes in a two way communication system. The rate of adaptation is often dynamic and varies over time. Disclosed are novel rates of adaptation that perform well in the presence of background noise, during double talk and with echo path changes. Additionally, the echo or residual echo can further be suppressed with non-linear processing performed using joint frequency-time domain processing.

Abstract: Many speakers, especially small speakers are susceptible to distortion if too much power is applied in certain vulnerable frequency bands. The distortion can be prevented by applying equalization to the audio signal driving the speaker. An equalizer can be configured to suppress the audio signal in the vulnerable frequency bands. The equalizer monitors the power in the vulnerable frequency bands and suppresses those vulnerable frequency bands only when they have sufficient power to distort. In this fashion, undesired audio effects due to the equalization can be avoided.

Abstract: An apparatus for providing real-time calibration for two or more microphones. A calibrator for receiving a left microphone signal and a right microphone signal and generating phase difference data. A phase and amplitude correction system for receiving one of the left microphone signal or the right microphone signal the phase difference data and generating calibration data for a beamformer. The beamformer receiving the calibration data, the left microphone signal and the right microphone signal and generating a monaural beamformed signal.

Abstract: Disclosed methods and systems measure acoustic responses to training signals activated prior to communication sessions. Profiles related to the acoustic responses are saved and adapted during communication sessions. Training signals may have uniform frequency distributions over a frequency range and may be in response to user inputs, timeouts, or predetermined events. In the next excessive divergence is detected, an adapted profile may be substituted by an original, trained profile.

Abstract: There is provided a method of redirecting an audio stream from a first audio endpoint to a second audio endpoint in a computer operating system. The method includes directing the audio stream from a client application through a first audio resource stack to the first audio endpoint; creating an audio endpoint bridge to provide a path for the audio stream from the first audio resource stack through a second audio resource stack connected to the second audio endpoint; and redirecting the audio stream to the second audio endpoint using the audio endpoint bridge. The audio endpoint bridge can be created by forming a bridging application so as to activate the second audio stack. The bridging application can be hooked into a Windows audio engine in the second audio resource stack. The bridge can be used to intercept an audio stream and remove noise from it. Additionally, a specific type of noise with sporadic intermittent spikes has been observed in this audio framework with certain Bluetooth headsets.

Abstract: A communication session is established between an APCM modem and a DPCM modem. The central office interrupts the communication session by transmitting a call-waiting alert signal to the APCM modem. In response to the alert signal, the APCM modem transmits a caller ID data request to the central office. The APCM modem further transmits an on hold notification to the DPCM modem to prevent the DPCM modem from terminating the communication session as a result of the interruption by the alert signal and/or receipt of the caller ID data by the APCM modem. The DPCM modem is placed on hold while the APCM modem answers the call waiting. Subsequently, the APCM modem initiates a quick connect procedure to re-establish the communication session with the DPCM modem.