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: A method for providing echo cancellation between a first and second communication unit detects an echo condition (200) between first and second communication units. In addition, the method includes detecting whether a decoded near end audio packet contains a suitable level of background noise to be used as a background noise packet. If so, the current near end encoded audio packet is stored (202) in a buffer (26), such as a circular buffer. Previous near end encoded audio packets (42) that are also determined to have a suitable level of background noise based on their decoded corresponding counterparts are also stored in the circular buffer. When an echo condition is detected with respect to a current near end encoded audio packet, the method includes substituting a previous near end encoded audio packet stored in the buffer as the next encoded audio packet for transmission (204).

Abstract: A network gateway is configured to facilitate on line and off line bi-directional communication between a number of near end data and telephony devices with far end data termination devices via a hybrid fiber coaxial network and a cable modem termination system. The described network gateway combines a QAM receiver, a transmitter, a DOCSIS MAC, a CPU, a voice and audio processor, an Ethernet MAC, and a USB controller to provide high performance and robust operation. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.

Abstract: Sub-band filtering, adaptive echo cancellation, and residual echo suppression are selectively and separately applied in hierarchical order under the control of a circuit that monitors four separate signals to determine n machine states. The number of machine states is further divided among m levels of noise in determining which, and how much of, sub-band filtering, adaptive echo cancellation, and residual echo suppression to use at any given time. A voice activity detector (VAD) is used to monitor each signal and provides statistical information in addition to whether or not a voice signal is detected. Sub-band filter, echo cancelling, and non-linear processing are not permitted to provide maximum reduction simultaneously. Even so, the invention provides at least 15 dB more echo suppression than systems without a sub-band filter bank series coupled with a non-linear processor in each channel.

Abstract: An echo canceller has a high-pass filter 11, a speaker 3, an A/D converter 6, and an echo canceller 7. The high-pass filter 11 suppresses a low-frequency component in a received signal. The speaker 3 outputs an acoustic sound of a low-frequency suppressed received signal passed through the high-pass filter 11. The A/D converter 6 converts an acoustic echo from a microphone 4 into a transmission signal of a digital form. The echo canceller 7 generates a pseudo echo signal based on the low-frequency suppressed received signal passed through the high-pass filter 11, and eliminates the acoustic echo to be inputted to the microphone 4 from the speaker 3 by subtracting the pseudo echo signal from the digital signal converted by the A/D converter 6.

Abstract: Methods and apparatus for echo and noise cancelation contemplate occasional saturation of an echo and/or noise containing source signal and control adaptation of a cancelation filter to minimize the detrimental effects of such source signal saturation. According to exemplary embodiments, filter coefficients of an adaptive filter are updated only when a prevailing value of the source signal is within a predetermined range of possible source signal values. Consequently, the filter response is not perturbed by source signal saturation, and the adaptive filter continues to provide quality echo suppression even immediately following periods of saturation.

Abstract: A method and apparatus that performs specific automatic gain control in an echo canceller (16). The disclosed method and apparatus utilize a low complexity algorithm that performs automatic gain control to achieve greater speed of convergence of the echo canceller (16) and an increased ability to distinguish between near-end speech and echo through the use of specific automatic gain control. A double talk threshold of the echo canceller is adjusted by using, in part, computed gains of inbound and outbound signals internally within the echo canceller in order to adjust the echo canceller double talk threshold.

Abstract: An echo cancellor having a main tap coefficient holding section to renew a tap coefficient used to establish a pseudo transmission characteristic of an echo path and a sub tap coefficient holding section to make a copy of a tap coefficient held by the main tap coefficient holding section and to hold it. The copying is made each time an echo suppressing rate is increased. Accordingly, a tap coefficient having a high echo suppressing rate is held by the sub tap coefficient holding section. In this state, if an ambient noise such as an alarm of whistle of a vehicle is mixed, renewal operation of the main tap coefficient holding section is halted and a tap coefficient held by the sub tap coefficient holding section is used. Even in the case of a divergence of the main tap coefficient, normal operation can be maintained by the tap coefficient held by the sub tap coefficient holding section accordingly.

Abstract: A method and apparatus is capable of detecting the presence of a non-linear echo path as well as transitions from non-linear echo path to linear echo path and vice versa. Additionally, when non-linear echo path is detected, the echo canceller (12) is configured to follow a prescribed logic routine that combats possible echo leak-through as a result of compromised cancellation due to non-linearity. This prescribed logic routine affords the echo canceller (12) protection against non-linear echo path by preserving an already converged state of the echo canceller (12) from possible divergence due to the occurrence of non-linearity in the echo path and thereby prevents echo leak-through that would occur due to divergence of the echo canceller (12).

Abstract: Echoes caused by discontinuities in a telecommunications transmission lines cause double talk which cause divergence problems with echo cancellers. Divergence problems in echo cancellers cause considerable problems in interactive caller response systems, they cause less problems if all parties to a call are human. One of the biggest problems is the effect of the echoes on automatic speech recognition systems. The echo canceller method and system presented cancels echoes to reduce their interference with ASR and yet provides stability in the presence of double talk.

Abstract: A method is presented for dynamic resource allocation in a speech signal echo canceler enabling more efficient echo cancellation and as a result the ability for an Integrated Circuit to handle additional channels than heretofore possible. This is accomplished by applying one or more of three efficiency enhancing strategies. First, no update of coefficients is computed or convolution performed if the power level of the far end speech signal is below a given threshold. Second, convolution is limited to the set of active taps (i.e., taps that account for most of the power in the echo). Third, new coefficients are computed only when the power of the error signal is greater than a given threshold. Lastly, the set of active coefficients is periodically updated. These strategies release computational resources from unnecessary computations and divert them to other channels that may be active.

Abstract: A speaker-phone that is operable to perform system change detection, double-talk detection and if desired, optimal step-size control. The invention differentiates between system change and double-talk and is operable to these two situations differently. The invention does not rely solely on the energy measurements that are employed by conventional speaker-phones. Highly reliable system change detection is offered when compared to conventional speaker-phones. The direction and the amplitude of the system change is measured with very good detection probability in the invention. For double-talk detection, the invention does not rely on assumptions that the far-end echoes are of lower amplitude that the near-end signal in performing double-talk detection. The invention performs double-talk detection within a large diversity of echo-paths and background noise levels. A designer may tune the speaker-phone system to ensure proper double-talk detection near low levels of the near-end signal.

Abstract: An active noise suppression system for use in noisy environments includes a dual microphone noise suppression system in which the echo between the two microphones is substantially canceled or suppressed. Noise is cancelled by the use of first and second line echo cancellers, which model the delay and transmission characteristics of the acoustic path between the two microphones. In a first embodiment, a noise suppression system acts as an ear protector, canceling substantially all or most of the noise striking the dual microphones of the ear set. In a second embodiment, a noise suppression system in accordance with the present invention acts a noise suppression communication system, suppressing background noise while allowing speech signals to be heard by the wearer.

Abstract: A periodic signal detector includes sample counting means for counting a number of samples between adjacent zero cross points in an input signal, the sample counting means outputting the number of samples between each time the number of samples between the adjacent zero cross points is obtained and continuing outputting the number of samples until a next zero cross point is detected, and periodic signal section detecting means for detecting a section, as a periodic signal section, in which the output from the sample counting means has a constant result.

Abstract: An echo canceler provided with a noise detecting section which holds signals showing a presupposed ambient noise such as a horn of a vehicle. The noise detecting section is adapted to monitor a sending signal received through a microphone and, while detecting such ambient noises in the sending signal, an adaptive filter outputs a pseudo echo existing immediately before the ambient noise is detected. Even during the generation of ambient noises, an echo noise can be eliminated and the generation of a foreign voice (noise) can be avoided as well.

Abstract: A communication device and method for detecting an infinite return loss (IRL) condition and temporarily halting or bypassing operations of an echo canceller in response to detecting that condition. The echo canceller includes an IRL detection module that analyzes the echo return loss and the echo return loss enhancement measured from the far-end and near-end signals. Based on the analysis, the IRL detection module determines whether to bypass the subtraction of the estimated echo in the outgoing near-end signal or continue normal operations.

Abstract: An echo cancellation device for reducing a magnitude of an echo occurring in a voice signal propagating in a channel of a communication system. The echo cancellation device is capable to selectively acquire an active operative mode and an inactive operative mode in response to a condition indicative of a level of echo present in the voice signal. In the active operative mode the echo cancellation device performs echo cancellation on the voice signal. In the inactive operative mode the echo cancellation device allows the voice signal to propagate without performing any echo cancellation.

Abstract: A speakerphone arbitration method is used to eliminate the effects of echo in imperfect telephone circuits. The method assumes that speech energy received at the speaker phone is an echo, unless the speech energy has characteristics that indicate it is not echo, such as the duration of the speech energy, and the time at which the speech energy is received relative to the time when the user of the speakerphone finishes speaking, or pauses while speaking. The method also may allow arbitration if the speech energy is more energetic than a typical echo, regardless of the duration or time when it is received.

Abstract: Frequency domain nonlinear processing techniques are applied in the context of echo suppression. According to exemplary embodiments, the filtering characteristic of a nonlinear processor is dynamically adjusted by comparing the power spectrum of a residual echo component of a communication signal with that of the overall communication signal itself. For example, the filtering characteristic can be adjusted so that the nonlinear processor blocks only those signal frequencies in which the residual echo is, in some sense, dominant. The disclosed techniques make full duplex communication possible during the entirety of a conversation, even while residual echo is being actively suppressed.

Abstract: An echo suppressor for bi-directional communications includes an echo canceler and a residual echo suppressor having variable gain. The gain of the residual echo suppressor is controlled based on a characteristic, such as the estimated energy, of the residual voice echo, or alternatively the entire residual echo, preferably on a per-frame basis. In some embodiments, the residual voice echo energy is compared against the estimated non-echo energy to determine the required amount of gain to apply so as to attenuate the residual voice echo below a psychoacoustic perception level. In some optional embodiments, comfort noise is added to the output signal after the residual echo suppressor in an amount that corresponds to the amount of signal energy loss through the residual echo suppressor. Thus, in some embodiments, desired voice and background noise (including local background noise and comfort noise) are used to mask the presence of residual echo.

Abstract: System and method for controlling an ancillary telecommunications device such as an echo canceller within a telecommunications system. The system and method include and involve a switching system that is configured to receive a call from a calling station and to route said call within said telecommunications system, and an ancillary telecommunications device that is configured to control a call processing parameter to affect the call. The switching system and the ancillary telecommunications device are coupled to each other via a channelized call data network. The channelized call data network is configured to communicate data corresponding to the call over at least one data channel. The ancillary telecommunications device may control the call processing parameter to affect the call based on a continuity test issued by the switching system to the ancillary telecommunications device prior to the call.

Abstract: Switching a mobile telephone for selectively receiving or transmitting a voice signal in a speakerphone mode by counting the number of the full-rate voice data received from the sender, and blocking the transmission path from the receiver to prevent the received voice data from being retransmitted through the receiver's microphone to the sender if the number of the full-rate voice data exceeds a predetermined value.

Abstract: An echo canceling system with self deactivation includes an echo canceller based on an adaptive filter, and an echo detector. The adaptive filter determines an estimate of an echo signal present in an untreated signal received from a “near” end of a communications channel. In order to produce an echo-canceled received signal, the echo canceller subtracts the estimated echo from the untreated received signal. The echo detector compares the energy of the untreated received signal and the energy of the echo-canceled received signal. The difference represents the energy in the estimated echo signal generated by the adaptive filter. If this energy is large, significant echo is present. The echo canceller remains activated, and the echo detector selects the echo-canceled received signal for output. If the estimated echo energy is small, little or no cancelable echo is present. The echo canceller is deactivated, and the echo detector selects the untreated received signal for output.

Abstract: A communication system includes an echo canceller and double-talk detector. The echo canceller includes an adaptive finite impulse response filter that generates an adaptive filter weight vector. The double talk detector computes a squared norm of the filter weight vector and detects an increase of the squared norm in order to detect double-talk status. Upon detection of double-talk status, operation of the echo canceller is suspended.

Abstract: Echo suppression control device in a voice communication system wherein a reference signal is sent over the system from a transmitting apparatus and comprising an echo canceller (16) for removing any echo signal from a primary signal received by the transmitting apparatus, and a residual echo suppressor (20) for removing the residual echo at the output of the echo canceller. The residual echo suppressor comprises means (24) for identifying speech echo intervals during which the primary signal contains mainly echo of the reference signal, and a gain control unit (22) for computing an estimation of the residual echo level, computing a target level of the residual echo and computing a suppression gain G to be applied during the speech echo intervals to the residual echo signal obtained after the application of the echo canceller, this suppression gain being the ratio between the target residual echo and the residual echo level estimation.

Abstract: A hybrid echo suppresser and associated methods of use provide echo suppression in a bi-directional communications system, while minimizing desired-voice signal disruption. The hybrid echo suppresser includes a linear echo canceller (LEC), a non-linear processor (NLP), and a control circuit. The LEC operates on an echo-causing signal to produce an estimated-echo signal, which is subtracted from an input echo-containing signal, thereby producing an echo-cancelled signal. The NLP operates on this echo-cancelled signal to eliminate residual echo arising from system non-linearities. The control circuit repeatedly compares the echo-containing signal and the estimated-echo signal to determine if the echo-containing signal includes a desired-voice component. If not, the control circuit operates the NLP in an echo-voice mode having substantial signal attenuation.

Abstract: A compander circuit (20) for echo cancellation in telecommunications apparatus with an estimator module (21) for estimating an echo coupling and a delay of a line echo and a characteristic module (23) with an associated multiplier (24) for controlling the short-time output level of zout(k) as a function of the short-time input level of zin(k) is characterized in that at all inputs and outputs of the compander circuit (20), a plurality of N communications channels are applied and outputted, respectively, at an N-fold clock rate as compared with a single communications channel; that all memory units in the compander circuit (20) are designed as multiplexer-buffer-demultiplexer (MBD) units (30); and that a modulo-N counter (26) is provided which controls all MBD units (30) so that in each of the MBD units (30), always the same memory cell (351, 352, 35N) assigned to a particular communications channel is addressed.

Abstract: A process for suppressing total echoes comprising a plurality of partial echoes in telecommunications (TK) equipment such as terminals, transmission systems, or switching equipment by means of adaptive FIR (=Finite Impulse Response) filters that simulate the total echo and subtract it from the echo-affected useful signal transmitted to the respective TK equipment, whereby n partial FIR filters are provided, which respectively simulate a partial echo, is characterized in that m parallel, mutually independent TK channels are provided with an echo suppression function and that for this purpose a variable sub-quantity of the partial FIR filters is assigned to a TK channel to be operated, respectively, as required depending on the number of partial echoes and the size of the occurring delay times between signal and echo.

Abstract: An equipment (1) for the suppression of whole echoes composed of several partial echoes in telecommunications (TC) equipment, such as end devices, transmission systems or exchange equipment, with the help of adaptive FIR (=Finite Impulse Response) filters, which reproduce the whole echo and extract it from the echo-laden useful signal and which has been transferred to the respective TC equipment, in which the homogeneous FIR filters or partial filters (10), each of which are able to reproduce a whole echo or partial echo, are implemented on a single ASIC (=Application Specific Integrated Circuit) (9) for the m parallel and independent TC channels n to be served; and in which the whole echoes or partial echoes to be reproduced can be calculated in real time in the ASIC (9) and in which a digital signal processor (4) is designed to control the ASIC (9) and set the filter settings, especially after the coefficient required to reproduce the echo is calculated on the ASIC (9).

Abstract: A threshold estimation method in a telephony system estimates downlink power Rx and uplink power Ry. Echo model parameter candidates ai and bi are recursively determined for delayed Rx values. The bi having the minimum value is selected as an echo model parameter b, and in the corresponding delay &Dgr; is identified as the current echo delay. The model parameter candidate ai having the same delay is selected as model parameter a. The current echo return loss ERL is estimated from the estimated values of a and b. The current clip level is estimated from the estimated value of ERL and the estimated value of Rx that was measured &Dgr; time steps previously.

Abstract: To be able to successfully compensate the echos occurring in bidirectional telecommunications systems, comprising for example 2-wire/4-wire converters and/or AD/DA converters and/or satellite transmission links, the echo coupling factor and echo delay time for a system must be determined with a very high degree of accuracy and independently of the double talk situation. For this purpose, in accordance with the invention a process is provided wherein, by analyzing a dialogue, states and time segments are determined in which the probability of an incorrect evaluation of the coupling factor between the transmission paths and the echo delay time is very low. To improve the measurement accuracy, auxiliary quantities dependent upon the speech dynamics and the characteristic curve of the speech signal are introduced.

Abstract: A method of controlling an echo canceller for providing an echo cancellation signal by subtracting an echo replica signal either from a transmit signal or a receive signal. The method includes the steps of a first step of performing a speech detection based on the echo cancellation signal provided by the echo canceller; a second step of detecting a double talk condition based on a result of the speech detection performed by the first step; and a third step of controlling a learning operation of the echo canceller based on a result of the double talk detection performed by the second step.

Abstract: An echo canceling apparatus suitable for multiplexed transmission lines is provided that achieves a short convergence time and a small number of arithmetic operations. Adaptive filters are located in respective transmission lines. Each adaptive filter adaptively controls tap positions such that tap coefficients are located in dispersive regions which are obtained by removing fixed delays from the impulse response in an echo path. A controller receives tap position information from the adaptive filters to mutually compare the convergence degrees among the adaptive filters. Thus, the controller respectively supplies coefficient update control signals to the adaptive filters so as to suppress coefficient adaptation of an adaptive filter whose convergence is leading compared with the others.

Abstract: An object of the present invention is to provide an echo canceller capable of generating, when the double-talk detection precision is degraded and the learning of a filter coefficient swings by noises, an echo replica signal using a filter coefficient having a low degree of error at the time of detecting a double-talk state. A backup filter coefficient is calculated by adding a predetermined weighting factor times a filter coefficient obtained by the learning and a predetermined weighting factor times the preceding backup filter coefficient stored in second storage means.

Abstract: A teleconferencing system having an echo canceller is configured for use at a large near-end conference location having a loudspeaker for acoustic reproduction of a received far-end telecommunication signal, a plurality of microphones and local acoustic amplification of the signals produced by the microphones. At least one first microphone is located relative to the loudspeaker such that the acoustic delay time between the loudspeaker and the first microphone is less than or equal to the tail length of the echo canceller. At least one second microphone is located relative to the loudspeaker such that the acoustic delay time between the loudspeaker and the second microphone is greater than the tail length of the echo canceller. Signals from the first and second microphones are provided to a mixer and are mixed to provide a send-input signal to the echo canceller.

Abstract: In accordance with the invention, from the characteristic curve of the speech signal there are derived pulse sequences which are dependent upon the frequency but not the amplitude of the speech signal, so that in the case of a real echo, independently of the attenuation, identical pulse sequences occur in the case of the transmitted signal and, with a time shift, in the case of a received echo. The correspondence between the pulse sequences of transmitted signal and received signal is an indication that the received signal is an echo of the transmitted signal.

Abstract: A hands-free communications unit employs a downlink peak power memory element (150, FIG. 1), a downlink voice activity detector (140), and an uplink voice activity detector (180). The downlink voice activity detector (140) evaluates the incoming signal to determine if the signal includes voice. In a similar manner, the uplink voice activity detector (180) determines if an outgoing signal includes voice. In the event that the incoming signal includes voice and the energy of the outgoing signal exceeds a threshold calculated from the peak power of the incoming signal, the uplink voice activity detector (180) indicates that a double-talk condition exists (350, FIG. 3). In the event that the incoming signal does not include voice, the uplink voice activity detector (180) compares the uplink signal to a voice threshold above a noise floor to determine if the outgoing signal includes voice.

Abstract: The invention relates to an acoustic echo canceller particularly well suited for use in a hands-free terminal or teleconference system. The echo canceller is designed to assess the inherent signal attenuation occurring in the analog loop that connects the terminal to the switch mechanism of the PSTN domain or the PBX domain. The echo canceller is then adjusted in accordance with the degree of signal attenuation manifested by the loop. For high signal attenuation levels, the degree of echo control at the terminal is reduced since the signal attenuation occurring in the loop itself will compensate for the reduction, allowing to reach the echo control target at the far end of the loop (switch side). This feature avoids overly attenuating the echo at the terminal by taking advantage of the inherent echo control provided by the local loop conductors.

Abstract: System and method for controlling a telecommunications device such as an echo canceller within a telecommunications system. The system and method include and involve a switching system that is configured to receive a call from a calling station and to route said call within said telecommunications system, and an ancillary telecommunications device that is configured to control a call processing parameter to affect said call. The switching system and the ancillary telecommunications device are coupled to each other via a channelized call data network. The channelized call data network is configured to communicate data corresponding to the call over at least one data channel. The ancillary telecommunications device may control the call processing parameter to affect the call based on a directive issued by the switching system to the ancillary telecommunications device during the call. The directive is contained within at least one channel of the channelized call data network.

Abstract: A system and method for controlling echo using zero echo path, ringing, and off-hook detection. When conditions for zero echo path are detected, the present embodiment bypasses echo cancellation by replacing the output signal with the input to the echo canceller. In addition, the present embodiment also provides ringing and off-hook detection which additionally evaluate when the output signal should be replaced by the input to the echo canceller. The system and method provides additional detection and control benefits to echo cancellers and can be implemented in echo cancellation systems without substantial change to the existing echo canceller.