1. A method of enhancing the signal-to-noise ratio (SNR) of measured electrocardiogram (ECG) signals, the method comprising: providing at least three cardiac input signals derived from the measured ECG signals; forming a first estimate from each of at least three pairs of input signals; forming a second estimate from each of the input signals; and obtaining conditional product (CP) signals by generating, from each first estimate and each second estimate, a conditional product wherein the obtained CP signals exhibit increased signal components and reduced noise components, thus producing an enhanced ratio of signal to noise components (SNR).