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United States Patents:
1 6,577,966 Optimal ratio estimator for multisensor systems

A signal processing technique can be effectively used for source separation, signal enhancement, and noise reduction when using a twin microphone system. The class of stochastic signals for which ratio-estimates can be computed from histograms is defined. This class fits real-world signals of interest such as voice signals. Theoretical computation in closed form of the optimal estimator for this class of signals is disclosed. Two practical implementation solutions are disclosed, as is a practical solution to exploit an echoic environment model. Furthermore, two novel techniques for signal demixing are presented. The application of the optimal estimator and the suboptimal estimator to the case of more than two channels is disclosed.

2 6,526,148 Device and method for demixing signal mixtures using fast blind source separation technique based on delay and attenuation compensation, and for selecting channels for the demixed signals

A delay and attenuation compensation-based BSS technique for source selection and noise reduction is provided for speech recognition applications. The undesired signals are attenuated in every situation and from every direction as much as possible. For this purpose, the direction of the input signals is determined. Depending on the direction of the undesired signals, the internal delay between the microphones is calculated. This internal delay is then used in subtracting the microphone signals from each other. Therefore, the invention gives not only a good directionality on average, but the best directionality for every listening situation. Furthermore, the channel selection problem is solved in conjunction with the BSS technique.

3 6,343,268 Estimator of independent sources from degenerate mixtures

A system that reconstructs independent signals from degenerate mixtures estimates independent Auto Regressive (AR) processes from their sum. The system includes an identification system and an estimator. A mixture of two signals is inputted into the system and through the identifying and filtering processes, two estimates of the original signals are outputted. The identification system includes an ARMA identifier, a computation of autocovariance coefficients, an initializer and a gradient descent system. The estimator includes filtering.

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