Abstract: A divergence detection device for an adaptive system comprising means for calculating the energy of an input signal of the system, means for calculating the energy of an output signal of the system and means for analysing the energy of the input signal and the energy of the output signal so as to detect a rise in the energy of the output signal, relative to the energy of the input signal, in case of divergence of the system.

Abstract: This device for processing audio signals for telecommunication equipment comprises automatic gain control means (18) acting on the level of the received audio signal (Sr) by amplifying and attenuating the signal as a function of the level of the received signal and echo cancelling means (22). The automatic gain control means (18) comprise amplification means (19-b) and attenuation means (19-a) for separately amplifying and attenuating the received signal downstream and upstream of the echo cancelling means (22), when considering the propagation direction of the received signal.

Abstract: An echo processing technique for attenuating echo components of a direct signal X1n in a return signal Y2n. A receive gain Grn and a send gain Gen are calculated. The receive gain Grn is applied to the direct signal and an input signal X2n is produced and emitted into an echo generator system. The send gain Gen is applied to an output signal Y1n from the echo generator system and the return signal Y2n is produced. A coupling variable COR is calculated which is characteristic of the acoustic coupling between the direct signal X1n or the input signal X2n and the output signal Y1n. The receive gain Grn and the send gain Gen are calculated on the basis of the coupling variable.

Abstract: The system for digitally processing an acoustic signal is arranged in a telephone set provided with a loudspeaker and a microphone, between the loudspeaker and the microphone. The system has an automatic gain control circuit associated with an echo cancellation device. It also comprises calculation means which are configured to apply a transfer function of the automatic gain control means to the echo cancellation device input, so that the signal from the microphone and the signal for the loudspeaker are each manipulated by a function comprising the same term, corresponding to the transfer function of the automatic gain control means.

Abstract: This device for processing audio signals for telecommunication equipment comprises automatic gain control means (18) acting on the level of the received audio signal (Sr) by amplifying and attenuating the signal as a function of the level of the received signal and echo cancelling means (22). The automatic gain control means (18) comprise amplification means (19-b) and attenuation means (19-a) for separately amplifying and attenuating the received signal downstream and upstream of the echo cancelling means (22), when considering the propagation direction of the received signal.

Abstract: A divergence detection device for an adaptive system comprising means for calculating the energy of an input signal of the system, means for calculating the energy of an output signal of the system and means for analysing the energy of the input signal and the energy of the output signal so as to detect a rise in the energy of the output signal, relative to the energy of the input signal, in case of divergence of the system.

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: A terminal in a communication system includes emitting and receiving transducers and an echo processor having an adaptive echo canceler that processes a residual echo output from the adaptive echo canceler.

Abstract: An echo processing technique for attenuating echo components of a direct signal X1n in a return signal Y2n. A receive gain Grn and a send gain Gen are calculated. The receive gain Grn is applied to the direct signal and an input signal X2n is produced and emitted into an echo generator system. The send gain Gen is applied to an output signal Y1n from the echo generator system and the return signal Y2n is produced. A coupling variable COR is calculated which is characteristic of the acoustic coupling between the direct signal X1n or the input signal X2n and the output signal Y1n. The receive gain Grn and the send gain Gen are calculated on the basis of the coupling variable.

Abstract: The invention concerns a method for adaptive control of multichannel acoustic echo cancellation system comprising N speakers HPi (i=1, 2, N), N being an integer not less than 2, and M microphones MCj (j=1, 2, M), M being an integer not less than 1. The system comprises N×M identification filters Fij with variable coefficients, the identification filter Fij enabling to estimate the acoustic coupling between the speaker HPj and the microphone MCj based on a pitch &mgr; adapting the variable coefficients. The pitch &mgr; adapting the variable coefficients is based on the presence or absence of signal in the speakers HPk (k≠i)?. The invention is applicable to the hands-free use of communication tools.

Abstract: A sound pick-up and reproduction system includes at least two sound sensors, such as microphones, situated at different distances from a sound reproduction device, such as a loudspeaker. A processor responds to amplitudes and phases of signals outputted by the at least two sound sensors to control a signal outputted to an amplifier and adapted to drive the sound reproduction device, thereby reducing echoes in the sound reproduction device output caused by acoustic coupling between the at least two sound sensors and the sound reproduction device.

Abstract: The present invention concerns a device for processing the echo in a communication system at a terminal comprising a first transducer (4) and a second transducer (5), the said echo processing device (1, 101, 201) for its part comprising an adaptive echo cancellation device (3, 103, 203).

Abstract: The output signals of the acoustic sensors of the antenna are subjected to a processing of the superdirective kind, with a constraint as regards the modulus and a non-linear constraint which fixes the incoherent noise reduction.The theoretical formulation of these constraints being as follows ##EQU1## the first constraint signifying that the total transfer function is a pure delay .tau., and the second constraint signifying that a limit is fixed for the incoherent noise reduction.The antenna is provided to improve the near-field reception.

Abstract: A device for programmable delay of an analog signal in an acoustic antenna that comprises at least one analog/digital converter circuit delivering, from the analog signal, a digital signal at a first sampling frequency, followed by a delay memory receiving the digital signal in write mode, making it possible to store M consecutive samples in memory. A circuit for write and read access to the delay memory is provided to address the delay memory in write and read mode, which, under read access control, delivers a series of samples delayed by a defined value, a function of the number of samples M stored therein. A sub-sampling circuit receives the delayed digital signal and delivers a sub-sampled delayed digital signal at a second sampling frequency less than the first sampling frequency.

Abstract: An acoustic antenna for computer workstation, used for video conferencing that comprises a plurality of microphones connected to a summator circuit. The microphones are distributed in a layout so as to form a substantially straight line and are each spaced with respect to a reference microphone placed in the vicinity of the vertical axis of symmetry of the screen of the workstation according to a specified law. The layout exhibits a substantially cylindrical directivity pattern whose axis of revolution is formed by the straight line.

Abstract: A system for selective sound capture for hands-free telephony and multimedia workstations of the acoustic antenna type with an aerial formed by a member with a concave cylindrical surface. The system includes a plurality of electro-acoustic transducers which are distributed over and in the vicinity of the cylindrical surface. Circuits for partial summation of a plurality of analog sound signals make it possible to form elementary acoustic antennas and a summation circuit produces a resultant analog signal representative of the sound signal arising from a useful speaking area.

Abstract: The device comprises an echo cancelling circuit receiving a first signal and a second signal and a real echo between channels for producing a third signal containing the second signal and a difference between the real echo and the estimated echo. Detectors detect the echo difference and the second signal in the third signal when the level of the third signal exceeds a predetermined threshold. Circuits gain-control the adaptation in the adaptive filtration of the echo cancelling circuit in such a way as to modify the adaptation gain when the second signal is not detected and to prohibit all filtration modifications as long as the second signal is detected. For instance, for an acoustic echo in a telephone set, the echo is not processed when the third signal contains a local speech signal as second signal.