Abstract: In a hands-free mode of speech communication, a loudspeaker produces acoustic energy of a distant signal from a far-end talker and a microphone produces a near-end signal containing a speech component representing the speech activity of a near-end talker or an acoustic echo component, or both. An echo replica is produced from the distant signal and a residual echo representing the difference between the near-end signal and the echo replica. The residual echo is used as a feedback signal to produce the echo replica. Using one of the near-end signal and the residual echo as a first input signal and the echo replica as a second signal, an estimate of the acoustic echo is produced when the speech activity of the near-end talker is low or zero. Using the acoustic echo estimate, the spectrum of the first input signal is shaped to produce a local signal for transmission to the far-end talker.

Abstract: An echo canceller circuit (200) and method performs cascaded echo cancellation and noise suppression in a non-interfering manner. The echo canceller circuit (200) includes pre-noise suppression logic (210), echo canceller coefficient logic (218), noise suppression logic (212) and an echo canceller filter (216). The pre-noise suppression logic (210) receives pre-echo canceller uplink data (64) and downlink data (52), and in response produces pre-noise suppression uplink data (224). The echo canceller coefficient logic (218) receives the pre-noise suppression uplink data (224) and the pre-echo canceller uplink data (64), and in response produces filter coefficient data (226). The noise suppression logic (212) receives the pre-noise suppression uplink data (224), and in response produces noise suppressed uplink data (228). The echo canceller filter (216) receives the noise suppressed uplink data (228) and the filter coefficient data (226) and in response produces final uplink data (230).

Abstract: The invention relates to methods for controlling adaptive filters, where a first step involves a first input signal, which has a narrowband frequency range and occurs at least intermittently during an adaptation phase in the filter, at the input of the filter prompting the adaptation phase to be continued until an echo signal which is conditional upon the first input signal and in the same frequency range is compensated for completely, a second step involves the adaptation phase being suspended when complete compensation for the echo signal has been achieved, and a third step involves the adaptation phase being continued if the first input signal is followed by a second input signal which has a narrowband frequency range and which differs from the frequency range of the first input signal at least by a frequency value, with the above steps being repeated starting at the first step, or with a fourth step involving a new adaptation phase being performed if the first input signal is followed by a third input sig

Abstract: A method and apparatus for use in suppressing acoustic echo in a target speech signal being transmitted through a packet-based communications network uses frame energy estimation applied to the target speech signal and to a reference speech signal. The method or apparatus estimates one or more reference speech energy levels in one or more reference packets based on one or more of the speech parameters generated by the speech encoding of the reference signal; estimates a target speech energy level in a target packet based on one or more of the speech parameters generated by the speech encoding of the target signal; compares the target speech energy level to one or more reference speech energy levels; and detects an echo in the target speech signal based on the comparison of the target speech energy level to the one or more reference speech energy levels.

Abstract: Techniques for suppressing large echo due to nonlinearity, instable adaptive filter, and so on. An echo cancellation system includes an echo canceller unit, a nonlinear echo detection unit, and a nonlinear echo suppression unit. The echo canceller unit (e.g., an adaptive filter) receives a reference signal and a near-end signal, derives an echo estimate signal based on the reference and near-end signals, cancels a portion of echo in the near-end signal based on the echo estimate signal, and provides an intermediate signal having residual echo. The nonlinear echo detection unit detects for large nonlinear echo in the echo estimate signal. The nonlinear echo suppression unit suppresses large nonlinear echo in the first intermediate signal based on a variable gain, which may be adjusted lower if large nonlinear echo is detected and higher otherwise.

Abstract: An echo canceller reduces an echo signal produced when the transmitted signal leaks back into the receiver via a hybrid. The echo canceller estimates the echo signal from the transmitted signal, and then subtracting the estimated echo signal from the received signal. In practice, the echo path channel in a DMT-modem is much longer than the cyclic prefix, and therefore, the received echo signal will be subjected to both ISI (inter-symbol-interference) and ICI (inter-carrier-interference). A traditional echo canceller, designed for a xDSL-modem, uses either a time domain adaptive FIR-filter or a combined echo canceller implemented in both time and frequency domain. A matrix-based adaptive echo canceller is implemented in the frequency domain. Various example embodiments are disclosed.

Abstract: In one aspect of the present invention, a method to reduce noise in a noisy speech signal is disclosed The method comprises: applying at least two versions of the noisy speech signal to a first filter, whereby that first filter outputs a speech reference signal and at least one noise reference signal, applying a filtering operation to each of the at least one noise reference signals, and subtracting from the speech reference signal each of the filtered noise reference signals, wherein the filtering operation is performed with filters having filter coefficients determined by taking into account speech leakage contributions in the at least one noise reference signal.

Abstract: The invention relates to a device for improving the transmission properties of a bundle of electrical data lines, particularly of a bundle of copper twin wires, and to a system for transmitting data that is provided with a device of this type. Said device comprises at least one adaptive filter, which generates an output signal for correcting the signal transmitted on a first data line. At least one signal tapped by a second data line or an external signal is used as a reference signal for the adaptive filter, and the corrected signal transmitted on the first data line is used as an error signal for the adaptive filter. According to the invention, the device is situated in the transmission path whereby improving the transmission properties of the cable independent from the switched-on transmission units and employed transmission techniques, particularly in the event of high bit rate transmission.

Abstract: A voice communicating apparatus in which a far-end voice of high sound quality can be outputted from a loudspeaker and an echo which is caused by the outputted far-end voice can be accurately removed with high precision. An analog far-end voice signal supplied from a telephone unit is directly outputted from the loudspeaker and a digital detection sound signal of the far-end voice and a near-end voice detected by a microphone is delayed by a predetermined time and supplied to an arithmetic operating part.

Abstract: The invention relates to a method for adaptive filtering in which a level of a reference signal necessary for the adaptive filtering is determined in the context of an adaptation by estimation, using a quantity equivalent to the reference signal, wherein the filtering is dependent on the electrical power of at least one signal extracted from a transmission channel to be filtered, and the equivalent quantity is determined by means of a mathematical function based on the electrical power of at least the extracted signal. The invention further relates to an arrangement with means for carrying out the method.

Abstract: Hands-free phones with voice activity detection using a comparison of frame power estimate with an adaptive frame noise power estimate, automatic gain control with fast adaptation and minimal speech distortion, echo cancellation updated in the frequency domain with stepsize optimization and smoothed spectral whitening, and echo suppression with adaptive talking-state transitions.

Abstract: An echo canceller, in which an adder adds a pseudo echo generated by an adaptive filter to an echo, so that the echo and the pseudo echo are canceled to each other, includes: a subband filter (8, 14) and a sampling converter (9, 15) for downsampling an audio signal; a selector switch (10, 16) which appropriately switches between a side performing the downsampling and another side performing fullband echo cancellation; and a tap arrangement controller (19) which optimizes a tap arrangement by using coefficients which are updated using a downsampled signal by the adaptive filter (11), the tap arrangement controller outputting the optimized tap arrangement to the adaptive filter (11) at time of the fullband echo cancellation.

Abstract: Techniques for simultaneously and efficiently eliminating echo and noise mixed in voice are disclosed. According to one aspect of the present invention, an adaptive filter system for eliminating noises and echo mixed in voice signal comprises a first signal adaptive filter, a first subtractor, a second adaptive filter and a second subtractor. The first signal adaptive filter estimates the noise mixed in the voice signal according to a reference noise. The first subtractor subtracts the noise estimated by the first adaptive filter from the voice signal to obtain a voice signal without the mixed noise. The second adaptive filter estimates the echo mixed in the voice signal according to a remote voice signal. The second subtractor subtracts the echo estimated by the second adaptive filter from the voice signal without mixed noise to obtain a clean voice signal.

Abstract: There is provided a method for use by an echo canceller to detect an echo path change and adjust to the echo path change. The method comprises determining a first bulk delay using a SPARSE foreground adaptive filter; configuring the foreground adaptive filter to an open-loop mode; canceling the echo signal based on the first bulk delay using the foreground adaptive filter; determining a second bulk delay of the echo signal using a SPARSE background adaptive filter; configuring the foreground adaptive filter to a closed-loop mode and continuing to cancel the echo signal based on the first bulk delay; configuring the background adaptive filter to the open-loop mode; measuring echo cancellation performance of the foreground adaptive filter and the background adaptive filter; and changing parameters of the foreground adaptive filter if the echo cancellation performance of the background adaptive filter is better than the foreground adaptive filter.

Abstract: An echo canceller is capable of reducing echo feeling in a conversation even if a tone signal is input. The echo canceller of this invention judges whether a far-end input signal is a calling control tone signal or not, and if that is the case, resets a coefficient of an adaptive filter. An echo canceller of another aspect judges whether a far-end input signal is a predetermined kind of a tone signal or not, and stops the update of the coefficient of the adaptive filter if the result is affirmative and an amount of echo cancellation is not larger than a threshold value. Further, when the tone signal ends, the echo canceller compares amounts of echo cancellation before and after the end of the tone signal, in accordance with a result of the comparison, restart the update of the coefficient of the adaptive filter after resetting the coefficient of the adaptive filter, or restarts the update of the coefficient of the adaptive filter without resetting the coefficient of the adaptive filter.

Abstract: The present invention provides a network apparatus capable of canceling far-end crosstalk (FEXT). When the network apparatus is under a training mode, hard data is provided to a FEXT canceller for performing FEXT cancellation. When the network apparatus is under a data mode, soft data is provided to the FEXT canceller for performing FEXT cancellation as well. Therefore, FEXT is effectively canceled, and consumption power of the network apparatus is saved.

Abstract: A method and apparatus for dynamically inserting gain in an adaptive filter is taught. This selective insertion of gain may be used to allow an adaptive filter to converge more quickly and/or to overcome inherent limitations of the adaptive filter. An echo canceller (e.g. 20 and 22 in FIG. 1) is just one possible use for an adaptive filter having a shorter convergence time. However, virtually all uses of an adaptive filter can benefit from a shorter convergence time and/or improved filtering performance.

Abstract: A method for canceling crosstalk, the method includes the steps of: filtering the signal corresponding to a far end crosstalk source in the frequency domain according to adaptive filter parameter; combining the received signal corresponding to a far end sending signal and the filtered signal in frequency domain corresponding to the far end crosstalk source. A device for canceling crosstalk and a signal processing system.

Abstract: An echo canceler is constituted of an adaptive filter for generating an echo replica simulating an echo occurring in an echo path lying between a speaker and a microphone, a subtracter for subtracting the echo replica from the sound received by the microphone, a double-talk detector which extracts a prescribed frequency band, in which the signal level is attenuated due to the echo path, from the output signal of the subtracter and which determines a double-talk event with respect to the extracted frequency band, and a controller for controlling the adaptive filter to update the echo replica in the double-talk event.

Abstract: Disclosed is a method and system adapted to receive an input signal from a far end transmission, to take in a near end return signal, and to inject into the return signal, prior to sending the return to the far end, a corrective signal whereby, for example, echoes in the return signal may be reduced or cancelled. A first exemplary embodiment includes one or more adaptive infinite impulse response (IIR) filters and one or more adaptive finite-impulse response filters (FIR) filters running in parallel each having an output that may be selected as the corrective signal based on filter performance determinations. A second exemplary embodiment includes an adaptive FIR filter outputting the corrective signal where the adaptive FIR filter has selected for it, based on filter performance determinations, an output of one or more adaptive IIR filters or a conditioned return signal selected as a reference.

Abstract: An echo canceler uses an adaptive filter to remove an echo of an incoming far-end signal from an outgoing near-end signal in the presence of ambient noise, updating the filter coefficients while the far-end signal is active and the near-end signal is inactive. The near-end and far-end signals are also sampled to obtain data vectors, which are averaged to generate simulated near-end and far-end signals, from which substitute filter coefficients are calculated and updated while the far-end signal is silent, the substitute filter coefficients being used when the far-end signal becomes active again. The number of data vectors averaged is varied according to the ratio of echo power to ambient near-end noise power, or according to the echo attenuation ratio, thereby speeding up convergence of the filter coefficients. Data sampled while the near-end and far-end signals are both active are excluded from the updating process.

Abstract: A signal processing system includes an AGC and pre-echo cancellation system for receiving an analog signal, amplifying signal magnitude (over all frequencies) to a pre-determined level by AGC, and removing the immediate transmit pulse from this received signal by pre-echo canceller to provide a second analog signal. The signal processing system also includes a summer for receiving the analog signal; a feed forward equalization (FFE) unit for receiving a signal from the summer; and a slicer for receiving a signal from the FFE unit and providing an output signal. The signal processing system also includes an Echo and NEXT or FEXT cancellation system for receiving the output signal and for providing a signal to the summer for canceling the echo and crosstalk in the signal processing system. The Echo and crosstalk components associated with a signal processing system can be subtracted prior to the FFE.

Abstract: Hands-free phones with voice activity detection using a comparison of frame power estimate with an adaptive frame noise power estimate, automatic gain control with fast adaptation and minimal speech distortion, echo cancellation updated in the frequency domain with stepsize optimization and smoothed spectral whitening, and echo suppression with adaptive talking-state transitions.

Abstract: A method and system receives a far-end signal and determines whether the far-end signal is representative of a modulated signal. The method and system also receives a near-end signal and determines whether the near-end signal is representative of a modulated signal. Predetermined characteristics of the near and far-end signals are determined as is whether the echo canceller will converge for the far-end signal. The operation of the echo canceller is controlled in response to the determination of the predetermined conditions and in response the determination of whether the far-end and near-end signals are modulated signals.

Abstract: In an embodiment, a method for removing an echo component is a first signal received at an audio input device includes outputting a second signal from an audio output device, receiving at the audio input device the first signal wherein the echo component in the first signal is the result of the second signal traversing an echo path; detecting if the first signal only comprises the echo component; determining an estimate indicative of the echo path by comparing the first signal and the second signal when it is detected that the first signal only comprises echo; applying the estimate indicative of the echo path to the first signal to determine an equalised first signal; comparing the equalised first signal with the second signal to determine an estimate indicative of the echo component; and removing the echo component from the first signal in dependence on the estimate indicative of the echo component; wherein the step of detecting if the first signal only comprises the echo component comprises comparing a char

Abstract: An echo canceller can efficiently remove the offset component from a voice call that can use an audio signal of a communication band wider than the conventional band and can provide a stable call with high communication quality.

Abstract: A path change is detected by multiplying the energy of a signal on the output of a summation circuit in one channel of a telephone by a constant to produce a product. The product is compared with the energy of a signal on the input of the summation circuit. A path change is indicated when the energy of the product exceeds the energy of a signal on the input of the summation circuit. The comparison is made in successive frames of an audio signal and a path change is indicated when the energy of a signal on the input of the summation circuit is exceeded in two or more successive frames.

Abstract: A voice recognition system includes an adaptive filter and a subtractor. The adaptive filter generates a simulated talk-back voice y(n) by setting a filter coefficient simulating a transfer system in which an input voice corresponding to a voice command and a talk-back voice output from a speaker are input into a microphone and by filtering a talk-back voice x(n). The subtractor extracts the input voice by subtracting the simulated talk-back voice y(n) from mixed sound input into the microphone. With this configuration, the talk-back voice is attenuated from the mixed sound including the input voice and the talk-back voice input tedinto the microphone, and then, the mixed sound is supplied to a voice recognition engine. Accordingly, the user can input his/her voice during a talk-back operation without the need to interrupt it by pressing a speech button every time the user wishes to input the voice. The voice recognition operation time can be thus reduced.

Abstract: Methods and apparatus for echo cancellation in a system having a speaker and a microphone are disclosed. The speaker receives a speaker signal x(t). The microphone receives a microphone signal d(t) containing a local signal s(t) and an echo signal x1(t) that is dependent on the speaker signal x(t). The microphone signal d(t) is filtered in parallel with first and second adaptive filters having complementary echo cancellation properties relative to each other. A minimum echo output e3(t) is determined from an output e1(t) of the first adaptive filter and an output e2(t) of the second adaptive filter. The minimum echo output has a smaller energy and less correlation to the speaker signal x(t). A microphone output is then generated using the minimum echo output e3(t).

Abstract: A method and apparatus for echo cancellation is disclosed. The apparatus includes an echo compensator and a double talk detector. The echo compensator compensates for associated feedback echo by filtering an echo component from a receiver input signal. The double talk detector provides a control signal based on comparisons of a receiver output signal to a threshold signal and to a transmit signal. The echo compensator also selectively updates filter parameters based on the control signal.

Abstract: Disclosed is a method and system adapted to receive an input signal from a far end transmission, to take in a near end return signal, and to inject into the return signal, prior to sending the return to the far end, a corrective signal whereby, for example, echoes in the return signal may be reduced or cancelled. A first exemplary embodiment includes one or more adaptive infinite impulse response (IIR) filters and one or more adaptive finite-impulse response filters (FIR) filters running in parallel each having an output that may be selected as the corrective signal based on filter performance determinations. A second exemplary embodiment includes an adaptive FIR filter outputting the corrective signal where the adaptive FIR filter has selected for it, based on filter performance determinations, an output of one or more adaptive IIR filters or a conditioned return signal selected as a reference.

Abstract: An echo canceller comprises foreground and background filters. The background filter locates and confirms peaks, defines active regions centered about the confirmed peaks and updates coefficients of the foreground filter when the background filter is more effective than the foreground filter A method for improved adaptive echo cancellation comprises configuring a foreground filter, calculating an echo-return loss responsive to the foreground filter, identifying the location of one or more peaks repetitively in a block of data in a background filter, confirming one or more identified peaks over a defined number of blocks before defining an active region equally about the identified peaks in the background filter, filtering the sparse impulse response responsive to the active regions, calculating an echo-return loss responsive to the background filter, and updating the foreground filter when the background filter includes a more effective set of filter coefficients.

Abstract: Techniques for finding the source of perceptual audio degradation in an IP telephony environment provide a hop-by-hop analysis of a network over which IP telephony is laid, and may be performed by network switching devices, such as routers, gateways and switches. Rather than monitoring packet loss, these techniques employ perceptual measures to determine the source of audio quality degradation in the network, as perceived by a user or caller. Generally, a reference waveform is systematically sent to intermediate network switching devices along the path between two endpoints. Each intermediate device sends back a return waveform that is based on the respective reference waveform received at each device. From comparing the reference waveform with the return waveform, for each round-trip along the path, the degradation of the audio quality is computed for each round-trip path, from which audio degradation is computed for each hop, from which the source of degradation is determined.

Abstract: A method for detecting echo path changes in an echo canceller using the statistics of the echo canceling behavior (i.e. signal and performance information), to distinguish between new line and double talk conditions. A moving counter is incremented or decremented based on monitored levels of ERL (Echo Return Loss), ERLE (Echo Return Loss Enhancement), noise and signal energies. When the counter reaches a predetermined threshold value indicative of sustained poor echo cancellation performance, a determination is made that there is a probable new line condition (i.e. echo path change). This echo path change information is then passed to the echo canceller to enable re-convergence.

Abstract: Methods and corresponding systems in an adaptive filter include calculating a signal estimator output using filter coefficients, and calculating an error signal. Next, a coefficient threshold is determined. Thereafter, for each filter coefficient, a first step size is assigned to filter coefficients with a magnitude less than the coefficient threshold, and a second step size is assigned to filter coefficients with a magnitude greater than or equal to the coefficient threshold. Finally, the filter coefficients are updated using the first and second step sizes and the error signal. The coefficient threshold can be selected as the average of the magnitudes of the filter coefficients. Alternatively, the coefficient threshold can be selected as the Mth largest of the filter coefficients ranked in order of magnitude. In one embodiment, the first step size can be less than one and the second step size can be greater than one.

Abstract: An echo canceller is proposed that has an echo path change detector (10) capable of reliably distinguishing an echo path change from the condition of double talk. The echo path change detector is adapted to sample filter parameters from an FIR adaptive filter in the echo canceller, and to detect a change in intensity in a pattern formed by the sampled filter parameters. An echo path change is signalled when the degree of said pattern intensity change exceeds a predetermined level. The invention resides in the understanding that the parameters or coefficients of the adaptive FIR filter react differently to a condition of double talk or echo path change. Specifically, when these parameters are sampled and represented as an intensity pattern, a significant change in this intensity pattern over time can indicate an echo path change.

Abstract: The invention provides a full-duplex communication device. In one embodiment, the full-duplex communication device comprises a first adaptive filter, a second adaptive filter, a channel decoupling module, and a frequency processing module. The first adaptive filter having a first tap length filters out echoes of a far-end talker from a first near-end signal carrying voices of a near-end talker according to a far-end signal carrying voices of the far-end talker to obtain a second near-end signal. The second adaptive filter having a second tap length less than the first tap length filters out echoes of the far-end talker from the first near-end signal according to the far-end signal to obtain a third near-end signal. The channel decoupling module processes the second near-end signal to generate a fourth near-end signal and subtracts the second near-end signal from the third near-end signal to obtain a fifth near-end signal.

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: Provided is a method for canceling background noise of a sound source other than a target direction sound source in order to realize highly accurate speech recognition, and a system using the same. In terms of directional characteristics of a microphone array, due to a capability of approximating a power distribution of each angle of each of possible various sound source directions by use of a sum of coefficient multiples of a base form angle power distribution of a target sound source measured beforehand by base form angle by using a base form sound, and power distribution of a non-directional background sound by base form, only a component of the target sound source direction is extracted at a noise suppression part. In addition, when the target sound source direction is unknown, at a sound source localization part, a distribution for minimizing the approximate residual is selected from base form angle power distributions of various sound source directions to assume a target sound source direction.

Abstract: A method and system for clear signal capture comprehend several individual aspects that address specific problems in improved ways. In addition, the method and system also comprehend a hands-free implementation that is a practical solution to a very complex problem. Individual aspects comprehended related to echo and noise reduction, and divergence control.

Abstract: A device is provided for measuring properties of transmission links by an adaptive filter. The device comprises a first output terminal adapted to provide a first signal to the transmission link. Further, the device includes a first input terminal for receiving an echo signal of the first signal. An adaptive filter forms a part of the device and is coupled to the first input terminal. The device includes a second output terminal for providing information identifying filter coefficient of the adaptive filter.

Abstract: Echo cancellation for audio/video conferencing uses an inaudible tone added at an originating conference site to the transmitted voice signal, for echo cancellation. The tone, upon receipt with the voice signal at a remote conferencing site and retransmission back to the originating site, is used to determine both the round trip delay of the conferencing link and the acoustic characteristics of the remote site, so as generate an echo cancellation signal for better audio performance.

Abstract: There is disclosed an echo canceller circuit for use in a full duplex transceiver of the type comprising a line driver capable of sending analog transmit signals through a cable and comprising a line receiver capable of receiving analog receive signals from the cable. An echo canceller impedance model circuit is coupled to an output of the line driver and is coupled to an input of the line receiver. The echo canceller impedance model circuit generates an echo canceller current that is equal in magnitude and opposite in phase to a current that represents signal echoes that are present in the analog receive signals. The echo canceller impedance model circuit has a variable impedance for generating the echo canceller current. The variable impedance has at least one variable resistor and at least one variable capacitor.

Abstract: Adaptive filters employing a normalized time domain least mean square algorithm having enhanced convergence rates by virtue of the use of an update gain greater than 2 ? max ? ? or ? ? 2 3 ? ? tr ? [ R ] .

Abstract: Disclosed is a non-linear echo canceller and method for cancelling echo during full duplex communication in a hands free communication system. An input signal from a far-end talker and an input signal from the output from an echo canceller are received. K spectral subbands are created for each input signal. The spectral echo residual power at each subband is estimated and compared to a clean signal power to calculate a signal to echo ratio. Gains are calculated based on each calculated ratio and non-linear echo is cancelled based on the calculated gains.

Abstract: A method is provided for reducing the adverse impact of echo on audio quality in a two-communication system. The method includes two parts. The first part begins by detecting non-linear effects (e.g. clippings and audio glitches). If a non-linear effect is detected, the system temporarily disables adaptation of the adaptive filter. In this way, filter coefficients obtained before the non-linear effect happens will not be corrupted, so the AEC can quickly recover from the non-linear effects. The second part begins by monitoring a parameter reflecting signal quality (e.g., ERLE). If the signal quality parameter falls below a given value the system switches from a full-duplex mode of operation to a half-duplex mode of operation. In this way, when a non-linear effect that is undetectable or occurs repeatedly (e.g., speaker volume changes) and which can corrupt an acoustic echo canceller (AEC) for a relatively long period of time, the system switches from full-duplex operation to half-duplex operation.

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: Cross-correlation based echo canceller controllers are described herein. By way of example, a system for controlling an echo canceller having one or more adaptive filters can include one or more adaptive filter controllers each corresponding to one of the one or more adaptive filters and each configured to halt adaptation of its corresponding adaptive filter according to the cross-correlation of its corresponding corrupted signal and its corresponding error signal of its corresponding adaptive filter.

Abstract: Hybrid echo canceller controllers are described herein. By way of example, a system for controlling an echo canceller can include a signal indicator and an echo canceller controller. The signal indicator can be configured to indicate periods of near-end signal and to indicate periods of echo only with echo-path change in the corrupted signal based at least in part on cross-correlation between two signals associated with the echo canceller. The echo canceller controller can be configured to control the echo canceller according to indications from the signal indicator.

Abstract: A non-echo canceling voice band modem capable of detecting subscriber alerting signal (SAS) tones and customer premises equipment alerting signal (CAS) tones is provided. The modem includes a shaping filter, an analog-to-digital converter (ADC), a SAS tone detector, a CAS tone detector and an echo canceler. The shaping filter, which is located in a transmitting path of the modem, filters modem signals to be transmitted from the modem. The ADC, which is located in a receiving path of the modem, converts any incoming analog signal to corresponding digital signals to be used by the modem. The echo canceler, which is coupled to the SAS and CAS tone detectors, cancels any echoes in modem signals before sending said modem signals to the SAS and CAS tone detectors.