Abstract: A technique is provided for filtering far-field electrical cardiac signals from near-field signals. Atrial tip and ring signals are sensed using unipolar electrodes and any timing differences between corresponding events within the signals are detected. Then, far-field signals are filtered from the tip and ring signals based on the detected timing differences, such that substantially only near-field atrial signals remain. The technique exploits the fact that near-field atrial signals are sensed when a conduction wave passes by the atrial electrodes. In contrast, far-field signals from the ventricles propagate to the atrium at near the speed of light. Hence, any significant timing difference between corresponding events appearing in the atrial signals is indicative of a near-field event, whereas the lack of a significant timing difference is indicative of a far-field event. In one example, a sense amplifier is provided with a Boolean logic circuit to aid in time delay-based filtering.

Abstract: The sound processor and method uses a model of basilar membrane motion to select stimuli, based upon the predicted motion which the acoustic signal presented would produce in an acoustically excited normally hearing cochlea. The filter; used, in contrast to single channel per electrode approaches, cover multiple channels and overlap with each other. Consequently the stimuli presented produce a neural excitation pattern which approximates the spatio-temporal travelling wave observed on the basilar membrane in an acoustically excited normally hearing cochlea. Preferably, the predicted electrode stimuli are based upon the instantaneous predicted amplitude of the electrode location.