1. A method of transferring to a receiver in real time content of segments of an audio signal transmission of a call, the method comprising: receiving from a call an audio signal as a sequence of segments including segments that have user characteristics that were registered to identify voices of users and other segments that do not have registered user characteristics; analyzing at least one segment of the received audio signal to determine if it contains voice activity; determining a probability level that the voice activity of the analyzed segment is of a registered user according to the registered user characteristics; and selectively transferring during the call the content of a segment to a receiver if the determined probability level is greater than a threshold value; wherein the content of segments of the same call, for which the determined probability level is less than the threshold value, is suppressed completely or partially.