France Telecom

France Telecom Sa

Pascal Scalart

Claude Marro

Franck Bouteille

Pierre Duhamel

Grégoire Le Tourneur

Andre Gilloire

Laurent Mauuary

Abdelkrim Benamar

Cyril Plapous

Christophe Beaugeant

The invention relates to a method of processing a noisy sound signal and to a device for implementing said method. The inventive method includes the following steps which are performed for each frame of a noisy sound signal, consisting in: applying a frequency-domain transform; estimating a power spectral density (PSD) of the noise for the frame; calculating a first noise reduction filter from the estimated PSD of the noise and from an estimation of the PSD of a wanted signal corresponding to the frame; filtering the frame with the aid of the calculated noise reduction filter, in order to obtain a first noise-corrected estimation for the frame; and obtaining a frame of a second signal from the first noise-corrected estimation of the aforementioned frame, comprising harmonics which are essentially at the same positions as the wanted signal corresponding to the frame of the noisy sound signal.

Method of processing a noisy sound signal and device for implementing said method

The device calculates a first frequency-dependent useful signal level estimator for the frame. The transfer function of a first noise-reducing filter is determined on the basis of the first useful signal level estimator and of a frequency-dependent noise level estimator. A second frequency-dependent useful signal level estimator for the frame is then calculated by combining the spectrum of the input signal and the transfer function of the first noise-reducing filter. The transfer function of a second noise-reducing filter is determined on the basis of the second useful signal level estimator and of the noise level estimator. The latter transfer function is used in a frame filtering operation to produce a signal with reduced noise.

Noise reduction method and device using two pass filtering

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.

Echo canceller in a communication system at a terminal

The device receives an input signal xand an observation signal y, one component of which is the response of a system to the input signal. It determines an error signal eat an instant t in accordance with the equation e=y&#x2212;XH, where His a vector made up of L coefficients of an identification filter having a finite impulse response representative of the impulse response of the system and X=(x, x, . . . , x). A predictive analysis of the input signal is performed by a computation applied to frames of the input signal. The L coefficients of the identification filter are adapted by adding to the vector Ha vector proportional towhere Uis a vector made up of the L values of a prediction residue of the input signal at the instant t and at the preceding L&#x2212;1 instants, and &#x3bb; is a positive or zero coefficient.

Adaptive identification method and device, and adaptive echo canceller implementing such method

A method and a device adapted to hands-free mobile radiotelephony for the optimized processing of a disturbing signal during a sound capture, on the basis of an observation signal y(t) formed of an original useful signal s(t) and of this disturbing signal p(t), the disturbing signal is estimated as a signal p(t) and the useful signal as an estimated useful signal su. An optimal filtering of the observation signal y(t) is carried out on the basis of the signal p(t) and of a minimizing of the error e(su,su) between the useful signal su and the estimated useful signal su. The estimated useful signal su and the useful signal converge towards the original useful signal s(t) for a substantially zero error e(su,su).

Method and device for the optimized processing of a disturbing signal

To estimate the response of a system to an input signal, on the one hand the input signal and on the other hand an observation signal, a component of which is said response to the input signal, are received, an error signal is determined by subtracting from the observation signal the input signal filtered by an identification filter representative of the response of said system, and the coefficients of the identification filter are adapted by taking into account the input signal and the error signal. If the adaptation takes into account an adaption stepsize .mu..sub.t, the latter is varied according to: .mu..sub.t =a/(c+d. P2.sub.t /P1.sub.t), where a, c and d denote positive constants, P1.sub.t denotes an estimate of the power of the input signal and P2.sub.t denotes an estimate of the power of the observation signal or of a disturbance component of said observation signal. The variable .mu..sub.t can also be employed to adapt the gains of an echo canceller with adaptive gains.

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Trebeurden, France

Pascal Scalart