Abstract: Hybrid echo canceller controllers are described herein. By way of example, a system for controlling an echo canceller can include a cross-correlator, a discriminator and an echo canceller controller. The cross-correlator can be configured to produce a cross-correlation based output that facilitates controlling the echo canceller by cross-correlating two signals associated with the echo canceller. The discriminator can be configured to produce a discriminator output that discriminates between near-end signal and echo in a corrupted signal. The echo canceller controller can be configured to control the echo canceller according to the cross-correlation based output and the discriminator output.

Abstract: An echo reduction method stores a received audio information stream. A sound detection flag is activated following detection of locally generated sound. Output based on the received audio information stream is muted in response to the activating the sound detection flag. Rendering status of the received audio information stream is saved, in response to the activating the sound detection flag, to reduce loss of audio information. At least a portion of the stored received audio information stream is rendered following inactivation of the sound detection flag.

Abstract: A howling control structure for a full duplex communication system. The structure is implemented as part of an acoustic echo canceller having a conventional transversal adaptive filter. A second transversal adaptive filter, shorter than the conventional filter, that adapts even in the absence of speech in its reference signal, is provided. The short filter adapts quickly and provides enough echo cancellation to prevent howling from occurring, even if the echo path is changed significantly during silence periods.

Abstract: Sound quality is enhanced in a sound system including handsets and headsets. Handset sound enhancing algorithms are implemented in a handset. The handset automatically determines which, if any, of a plurality of headset sound enhancing algorithms are active in a headset in communication with the handset. The handset determines how to use the handset sound enhancing algorithms in a sound processing channel based on which of the headset sound enhancing algorithms are active in the headset.

Abstract: System and method for processing communication signals in a communication system having a detector for detecting a parameter of a communication signal. A communication signal is provided to a non-linear processor (NLP) adapted to examine the signal and to decide whether or not to enter an active state based upon a parameter of the signal. If the NLP enters an active state, the NLP performs non-linear processing on the signal. The NLP communicates to the detector whether the NLP is active or inactive. If the NLP is active, a processing step of the detector is disabled.

Abstract: There is provided a method for use by an echo canceller to cancel a far echo at a variable delay and a near echo at a fixed delay. The method comprises constructing an echo signal model based on an incoming signal, determining a variable echo delay for a far echo caused by a far echo source, determining a fixed echo delay for a near echo caused by a near echo source, subtracting the echo signal model from an outgoing signal at a window placed around the variable echo delay to cancel far echo, e.g. when the echo canceller determines existence of the far echo, and subtracting the echo signal model from the outgoing signal at a window placed around the fixed echo delay to cancel near echo, e.g. regardless of existence of the near echo, wherein the fixed echo delay is smaller than the variable echo delay.

Abstract: Sound quality is enhanced in a sound system including handsets and headsets. Handset sound enhancing algorithms are implemented in a handset. The handset automatically determines which, if any, of a plurality of headset sound enhancing algorithms are active in a headset in communication with the handset. The handset determines how to use the handset sound enhancing algorithms in a sound processing channel based on which of the headset sound enhancing algorithms are active in the headset.

Abstract: A conference terminal for a digital voice conference system comprises a first sound transducer means, which is implemented to generate a microphone signal from an acoustic signal, a second sound transducer means, which is implemented to generate an acoustic signal from a loudspeaker signal, a connecting means, which is implemented to enable a connection between conference terminal and a conference central unit, to receive a composite conference signal from the conference central unit, and a means for echo suppression, which is implemented to combine the microphone signal or a signal derived therefrom in a noise suppression means with a composite conference signal in a listening operation of the conference terminal, such that a loudspeaker signal results, in which the acoustic signal, on which the microphone signal is based, is reduced.

Abstract: The present invention provides mechanisms for removing duplicate signals during a communication session. More particularly an over-air signal is received at a given endpoint and a stream of electronic data is monitored at the same endpoint for a duplicate to the over-air signal. If a duplicate is detected in the electronic data stream, it is removed so that only one occurrence of the signal is received at the endpoint.

Abstract: The present invention relates generally to tone detection in echo canceling systems, and more particularly to a method of monitoring oscillations of adaptive filter coefficients for narrow band tone detection in echo cancellation systems. The invention is directed at improving communication in a telephone communication network having one or more hybrid connections. A method for detecting continuous tones in an echo canceling system having an adaptive filter is provided. Continuous tones have a deleterious effect on the performance of adaptive filters. In the present invention, the adaptive filter coefficients are monitored. Oscillation of those coefficients indicates continuous tone presence.

Abstract: A signal identification method comprises receiving an incoming signal having incoming frames; receiving an outgoing signal having outgoing frames; extracting outgoing features from a current frame of the outgoing frames; extracting incoming features from a first previous frame of the incoming frames; calculating first feature distances based on corresponding outgoing features and incoming features; deriving a first score based on the first feature distances; extracting incoming features from a second previous frame of the incoming frames; calculating second feature distances based on corresponding outgoing features and incoming features from the second previous frame; deriving a second score based on the second feature distances; and determining whether the outgoing signal includes the incoming signal based on the first score and the second score.

Abstract: An echo canceling circuit comprising a double talk detector, an upper band signal filter configured to pass only near-end upper band signals to the double talk detector and remove lower band signals, an adaptive filter circuit, a control circuit operatively coupled to the double talk detector and to the adaptive filter circuit, and a threshold estimator configured to iteratively calculate an upper adaptive decision threshold value and a lower adaptive decision threshold value. The double talk detector declares near-end speech to be present if an estimated power level of the upper band signals exceeds the upper adaptive decision threshold value, and declares the near-end speech to be absent if the estimated power level of the upper band signals falls below the lower adaptive decision threshold value for a predetermined number of iterative cycles.

Abstract: Devices, softwares and methods send a warning signal when a periodic signal is present in the audio content of a VoIP connection. In response to the warning signal, an acoustic echo canceller of an IP telephone discontinues its adapting process. A signaling network switch detects when a periodic signal is present in the audio content, and issues a warning signal. A signaling call manager device, when it transmits a tone that has periodicity, it also transmits a warning signal.

Abstract: A method for optimizing voice quality in an analog trunk is provided. The method includes setting a loop parameter to optimize an Echo Return Loss (ERL) property for a loop distance, generating a tone according to a value of the loop parameter and measuring ERL values from the tone, and setting a loop parameter value corresponding to a smallest ERL value of the measured ERL values, as an optimized loop parameter.

Abstract: There is provided a method of detecting an infinite echo return loss (ERL) in an echo cancellation system while in a finite ERL mode. The method comprises determining a running mean attenuation by the echo cancellation system, determining a ratio of an echo signal to a near-end noise ratio (ENR), defining an infinite ERL threshold (THinfinite) as a function of the ENR, and switching to an infinite ERL mode as a function of the running mean attenuation and the THinfinite. The running mean attenuation can be enhanced echo return loss (ERLE), and the higher the ENR the higher the THinfinite and the lower the ENR the lower the THinfinite. The switching can further be a function of an energy distribution, where the switching switches to the infinite ERL mode based on a non-localized energy distribution over an echo path delay for a predetermined period of time.

Abstract: A method for seamless noise suppression on wideband to narrowband cell switching is described. In one embodiment the method includes applying noise suppression to a telephone signal using a first noise suppressor while operating a telephone in a first operating mode, the first noise suppressor generating an estimate of a noise components of the telephone signal; switching the telephone from the first operating mode to a second operating mode; providing the estimate of the noise component as an input to a second noise suppressor different from the first noise suppressor, when the switching step is performed; and applying noise suppression to the telephone signal using the second noise suppressor by using the estimate of the noise component provided by the first noise suppressor when the switching step is performed.

Abstract: An apparatus and method for disabling an echo canceller in a communication channel is external to the echo canceller. The average power of the received signal is compared to the average power of the transmitted signal and if the received signal is more than 26 dB below the transmitted signal, then it is determined that echo cancellation is not required. If the received signal is less than 6 dB below the transmitted signal, then there is double talk present and a determination can not be made. The invention provides a low cost system for controlling echo cancellers and can continue to monitor echo during a call. The invention is well suited to implementation on a field programmable gate array (FPGA) or application specific integrated circuit (ASIC).

Abstract: A method and apparatus for adapting dual filters is disclosed. In one aspect, a method may include transforming a signal, adapting a first adaptive filter based on the transformed signal, estimating a delay of an impulse response based on the adaptation of the first filter, delaying a signal based on the estimated delay, and adapting a second adaptive filter based on the delayed signal. In one aspect, an echo or other unwanted signal may be reduced or cancelled based on the adaptation of the second filter.

Abstract: An audio communication system and method with improved acoustic characteristics features a stereo detector that is introduced in the echo canceller of the system. When stereo in far-end audio is detected, converging of the adaptive mono model of the canceller is suspended, and when stereo in far-end audio is not detected, converging of the adaptive stereo model of the canceller is suspended. The system may also be extended with a miscellaneous processing unit configured to attenuate the signal at certain events implying a large stereo echo contribution. A stereo collapsing unit is also introduced on the channels of the far-end audio to remove the stereo image at certain events to further suppress the echo contribution.

Abstract: An echo detector has a correlator for correlating between an incoming signal and an echo signal, the correlator being arranged to operate recursively, the detector being arranged to detect the echo and the length of its delay from peaks in the correlation. Recursive operation means the computational load can drop from being proportional to N*N, to being proportional to 2N, where N is a number of samples in a correlation window. It also reduces computation delay. A filter at the inputs of the correlator suppresses low frequencies corresponding to the strongest components of pitch in human speech. Such filtering can remove periodic components which can mask a distinct peak of an echo. A classifier thresholds a ratio of highest and next highest correlation peaks beyond a time margin around the highest correlation peak, to reduce erroneous detections. It can classify two or more ratios simultaneously as distinct echoes.

Abstract: Plural echo cancellors each are tuned for different hybrid delays until it is established which echo cancellors are operating to cancel echos. The echo cancellors not so operating are then terminated.

Abstract: An echo removing apparatus for reducing the echo caused by sound returning from a speaker to a microphone of a small-sized communication terminal, such as a portable telephone. The echo removing apparatus includes a filter unit for outputting a pseudo echo signal estimating an echo component returning to the microphone based upon a generated sound signal supplied to the speaker, a subtractor for subtracting the pseudo echo signal supplied from the filter unit from the sound generated collection signal supplied from the microphone and a first characteristics conversion unit for converting frequency characteristics of sound generated collection signals from the microphone on the frequency axis. The characteristics of the filter unit are controlled for minimizing an error component between an output signal of the first characteristics conversion unit and an output signal of the filter unit.

Abstract: A method for reducing transmit echo in a DSL modem comprises selecting at least one cancellation device of a plurality of cancellation devices. An attenuation signal is generated using the selected cancellation device. At least a portion of transmit echo is removed from a receive signal using the attenuation signal.

Abstract: In a system in which echo transferred from a received signal to an outgoing signal is canceled by subtracting an adaptively predicted echo signal from the outgoing signal, howling is detected by detecting the effect of the predicted echo signal. The detected effect preferably depends on the magnitude or polarity of the predicted echo signal. The effect may be detected by comparing an envelope of the received signal or outgoing signal with a corresponding envelope of the residual outgoing signal left after echo cancellation. The echo attenuation on the echo path from the received signal to the outgoing signal may also be calculated, the conditions for howling detection being made more stringent as the detected echo attenuation increases. When howling is detected, it may be suppressed by attenuating the residual outgoing signal or initializing an adaptive filter that generates the predicted echo signal.

Abstract: A multichannel source activity detection system, e.g., a voice activity detection (VAD) system, and method that exploits spatial localization of a target audio source is provided. The method includes the steps of receiving a mixed sound signal by at least two microphones; Fast Fourier transforming each received mixed sound signal into the frequency domain; filtering the transformed signals to output a signal corresponding to a spatial signature of a source; summing an absolute value squared of the filtered signal over a predetermined range of frequencies; and comparing the sum to a threshold to determine if a voice is present. Additionally, the filtering step includes multiplying the transformed signals by an inverse of a noise spectral power matrix, a vector of channel transfer function ratios, and a source signal spectral power.

Abstract: A noise level calculator for detecting noise in a telephone line echo canceller that utilizes adaptive filters enables silencing of noise switching so that it is not heard on the far end side. The calculator promotes determining whether the reference signal applied to the adaptive filter is a noise or non-noise segment. The calculator operates by calculating the difference in energy of two sample windows, calculating the difference in the energy of the signal within each of the sample windows, updating a variance parameter based on the difference, and performing further alternative operations based on the value of the variance parameter.

Abstract: A telephone (310) and a method for providing outbound audio when the telephone is operating in a speakerphone mode. A first data unit (350) including a first unit type identifier (360) can be received by the telephone. The first unit type identifier can be an indicator of a type of audio data contained in the first data unit. For instance, the first unit type identifier can indicate whether the audio data is music or non-music audio data. If the first unit type identifier has a first value, for example a value indicating that the audio data is music data, unmuted outbound audio reproduced from the first data unit can be provided and voice activity detection can be disabled. Additionally, inbound audio can be muted.

Abstract: A computer apparatus is provided, which has a multipath acoustic output system and a multipath acoustic input system, which includes parts for enabling an adaptation of the filter of an acoustic echo canceller incorporated in the computer apparatus that is always precise regardless of the chronological delays of the components of the computer apparatus, wherein the chronological delays are variable for acoustic signals.

Abstract: A switching center for use in a communication network includes a pool of echo cancellation units for use in providing echo cancellation services to users associated with the switching center on an “as needed” basis. A communication connection being supported by the switching center is analyzed to determine whether intolerable reflections are being received from an associated trunk. If such reflections are detected, one of the echo cancellation units in the pool is assigned to the communication connection for use in reducing or eliminating the reflections. When the communication connection terminates, the echo cancellation unit is returned to the pool for subsequent use with another communication connection.

Abstract: The invention relates to a communications network, including switching centers having no echo canceling equipment and switching centers having echo canceling equipment. The switching centers are capable of changing the call party or the call during the call. The switching center which controls the change of call party or call type is arranged to command the nearest switching center having the echo canceling capability to connect/disconnect an echo canceling equipment to/from the connection. In other words, in these special situations the echo cancellation is controlled by a new signaling feature within the communications network.

Abstract: A multichannel full-duplex audio signal transmission system, comprising an adaptive filter (2) provided for multichannel acoustic echo cancellation. A channel combining device (5) is provided between the preprocessing units (V1, . . . VD) and loudspeakers (L1, . . . ,LD), in which several (C>D) loudspeakers can be connected to one and the same preprocessing unit and by means of which the remaining D-C preprocessing units can be separated from the loudspeakers (L1, . . , LD). The channel combining device permits an optimization of the convergence ratio of the adaptive adjustment of filter coefficients in said adaptive filter (2).

Abstract: A double talk activity detector (30) and method for an echo canceler circuit (10) improves the probability of detecting a double talk condition based on at least pre-echo canceler uplink data (40). The echo canceler circuit (10) includes a double talk activity probability data generator (30) and an echo canceler stage (20). The double talk activity probability data generator (30) receives pre-echo canceler uplink data (40) and in response produces double talk activity probability data (50). The echo canceler stage (20) is coupled to the double talk activity probability data generator (30) and receives downlink data (60), pre-echo canceler uplink data (40) and the double talk activity probability data (50) and in response produces attenuated uplink data (70).

Abstract: A method for adaptive control of a multi-channel echo cancellation system including N loudspeakers, where N is an integer greater than or equal to 2, and M microphones, where M is an integer greater than or equal to 1. The system includes N×M identification filters with variable coefficients, the identification filters being used to estimate acoustic coupling between the loudspeakers and the microphones as a function of a variable coefficients adaptive step. The variable coefficients adaptive step depends on whether or not there is a signal present on the loudspeakers. The method is applicable to hands-off operation of communication tools.

Abstract: Methods and apparatus compensating for background noise associated with a transmitted signal. In a first embodiment, an adder combines an echo estimate with the the transmitted signal to form a processed signal, a noise reduction circuit uses a background noise estimate to subtract the background noise from the processed signal, and a non-linear processor uses the background noise estimate to combine a compensating background noise signal with the proccssed signal. In another embodiment, the noise reduction circuit divides the processed signal into sub-bands. With variations of an embodiment, the nonlinear processor is a sub-band non-linear processor, the processed signal is divided into sub-bands, and the background estimate includes sub-band noise estimates.

Abstract: A non-linear processor for use in an echo canceller is set forth. The non-linear processor includes a center clipping digital filter receiving an echo compensated signal. The non-linear processor provides a center clipped output signal having non-linear thresholds at values of +TNLP and ?TNLP. The value of TNLP is dynamically dependent, at least in part, on echo return loss measurements. To limit the processor's susceptibility to corruption from double-talk conditions, the non-linear processor inhibits the dynamic setting of the TNLP value when a double-talk condition is present. Additionally, or in the alternative, the non-linear processor locks the value of the echo return loss measurement after a predetermined number of consecutive echo return loss measurements have values falling within a predetermined range of one another. Such locking further reduces the susceptibility of the non-linear processor to corruption from double-talk conditions.

Abstract: Methods and apparatus for processing a received voice signal from a variable-delay network by a communications system that has at least one echo canceller. An echo canceller determines delay characteristics that are associated with the received voice signal and correspondingly modifies echo cancellation processing. In a variation of the embodiment of the invention, a first echo canceller sends silence descriptor information to a second echo canceller. The second echo canceller reconstructs a voice signal based upon the silence descriptor information and excitation vector information.

Abstract: A method of controlling an echo canceller in a communications channel, is disclosed wherein input signals from the communications channel are first subbanded into a subband. Echo locations are then identified within the subband and are used to control the echo canceller. Typically, the echo canceller will be a fullband echo canceller with an adaptive filter, in which case the echo locations are used to control the filter coefficients.

Abstract: A telephone includes a transmit channel and a receive channel, each including a bank of sub-band filters having a VAD coupled one to each sub-band filter. Each VAD measures the spectral energy in a sub-band, compares the spectral energy to a first threshold, and produces an output signal representative of whether or not the first threshold is exceeded. The voice activity detector also includes a threshold circuit for calculating a dynamically adjustable noise threshold based upon averaged measured spectral energy. A wide band or system VAD monitors echo canceling circuitry to detect voice activity and double talk. A dynamic balance control circuit maintains the transmit and receive channels in a predetermined energy ratio during double talk.

Abstract: A telephone includes a first channel having a microphone input and a line output, a second channel having a line input and a speaker output, and each channel having a plurality of band pass filters with their outputs coupled to a multiplex circuit. The multiplex circuit selects subsets of the signals in each channel in accordance with the magnitudes of the signals in each band. Thus, full duplex operation is provided in accordance with the spectral content of each channel. In one embodiment of the invention, the multiplex circuits initially allocate alternate bands within each channel and complementary bands between the channels, thereby emulating a complementary comb filter. Thereafter, bands are allocated according to spectral content.

Abstract: A communication system having an echo canceller is disclosed. One embodiment of the echo canceller includes an adaptive filter used to provide an estimate of reflected echo which is removed from the send signal. The echo canceller may also include a near-end talker signal detector which may be used to prevent the adaptive filter from adapting when a near-end talker signal is present. The echo canceller may also include a nonlinear processor used to further reduce any residual echo and to preserve background noise. The echo canceller may also include a monitor and control unit which may be used to monitor the filter coefficients and gain of the adaptive filter to maintain stability of the echo canceller, estimate pure delay, detect a tone, and inject a training signal. The echo canceller may also include a nonadaptive filter used to reduce the length of the adaptive filter.

Abstract: A method of estimating an echo return loss of a communication link measures the peak power value of a signal received from a far end of a communication link and the corresponding peak power value of a signal received from the near end of the communication link. When the near end signal is free from near end voice and excessive noise, the near end corresponding peak will be the echo of the far end power. The far end power is monitored and when a peak is detected, a period, which can be equal to a filter length period, is initiated. When the period has run, the delay line attached to the near end is polled to determine the peak power in the delay line. This peak power will correspond to the far end peak. If a peak, exceeding the first peak is detected before the period has run, the period is reinitiated. The echo return loss estimate is calculated as a ratio of the far-end peak power value to the near-end peak power value.

Abstract: A method includes receiving a plurality of packets from at least two voice packet streams. The method also includes generating at least two voice signals using the plurality of packets. Each voice signal is associated with one of the voice packet streams. In addition, the method includes identifying an echo of one of the voice signals in at least one other of the voice signals.

Abstract: An echo canceler includes an adaptive filter that adapts to changes in an echo path, a double-talk detector, and an echo path change detector. The echo path change detector estimates the loss on the echo path, thereby distinguishing true double-talk from apparent double-talk detected by mistake because of a change in the echo path. The adaptive filter continues normal adaptation during the apparent double-talk state when echo path change is also detected. The necessary conditions for detection of echo path change preferably include a small separation between the estimated loss on the echo path and a long-term smoothed value of the estimated loss. The echo path change detector is useful in, for example, the cancellation of line echo in telephone switching systems.

Abstract: An echo canceller includes two parallel filters and a controller. The controller chooses the best of the two filters for the final echo cancellation. The filter coefficients are exchanged between the two filters constantly so that both filters retain performance all the time even if double-talk and echo path variations occur very closely in time. One filter is strongly robust and will not diverge during double-talk, and another filter is weakly robust and will converge rapidly during echo path variation.

Abstract: A method and apparatus for reducing echo feedback in a wireless communication system (10) is accomplished when a receiving communication unit (24) senses a feedback signal, or echo, via an ancillary communication path. The receiving communication unit is a targeted recipient of an original audio signal generated by a transmitting communication unit (22), where the original audio signal (42) is conveyed to the receiving communication unit. Upon detecting the feedback signal and determining that it exceeds a feedback threshold, the receiving communication unit attenuates an audible output of the original signal to reduce echo to the transmitting communication unit. In addition, the receiving communication unit, and/or the transmitting communication unit include echo canceller to further minimize the echo within the digital communication system.

Abstract: The invention provides an apparatus and method for bulk delay insertion prior to echo cancellation, with echo suppression. The exemplary apparatus embodiment (100) bandpass filters (120) and down samples (130), by a down sampling factor, a reference signal and a combined signal that includes an echo of the reference signal. An adaptive echo delay filter (140) determines a plurality of filter coefficients, using the down sampled reference signal, and using an error signal formed as a difference between the down sampled combined signal and the adaptive echo delay filter output. When the filter coefficients have converged, an echo delay time period is determined as a product of the tap location of the maximum filter coefficient and the down sampling factor. When the echo delay time period is greater than the capacity of an associated echo canceller, an adaptive delay inserter (110) inserts the echo delay time period prior to echo cancellation.

Abstract: A process is described which generates matrix coefficients using zero-lag auto and cross-correlations from signals commonly found in echo cancellers. Double-talk and path changes are then detected using matrix operations such as determinants, eigendecompositions, or singular value decompositions (SVDs). In a preferred embodiment, the determinant of the correlation-based matrix is compared against predetermined threshold values.

Abstract: Controlling echo cancellation includes receiving signals associated with a call. A signal of the signals is detected. Whether the detected signal is a high speed signal or a low speed signal is determined. Echo cancellation is disabled if the detected signal is a high speed signal. The echo cancellation is enabled if the detected signal is a low speed signal.

Abstract: A method for allocating echo canceling devices in a telecommunications network having at least two networks connected to one another by network switching nodes. The network switching nodes have trunk groups interconnecting the networks so that connected terminal devices can be connected to one another. Devices for canceling echo are provided in the networks and can be requested and, if certain criteria are fulfilled, inserted into existing connections to cancel echo signals. The method includes marking selected trunk groups originating from or leading to another network with an echo cancellation mark characteristic, and providing available echo canceling devices based upon the echo cancellation mark characteristic when echo canceling is requested for a connection being set up through one of the selected trunk groups. A system for allocating echo canceling devices in a telecommunications network is also provided.

Abstract: Provided is a method and apparatus for inband testing of an echo canceller. The apparatus includes a signal generator for generating an excitation signal including a preamble portion and a test portion. The echo canceller receives the excitation signal at a decoder. The decoder differentiates the preamble from the test portion and obtains control information by decoding the preamble portion. A controller configures the echo canceller during testing according to the control information obtained from the preamble portion. A strength of the present invention is that the preamble portion allows precise control of the echo canceller during testing by synchronizing the test control to the location of the preamble. This allows exacting control of the echo canceller during testing to within a single sample time of the excitation signal, e.g., 125 microseconds.