Abstract: A security method compares a present verbal utterance with a previously recorded verbal utterance by comparing time-frequency domain representations of the utterances, with multiple repeat utterances forming a basis for determining a variation in repetitious performance by an individual, and similar differences between enrollment and challenge utterances forming a basis for a similar analysis of variance between enrollment and challenge utterances. In one embodiment a set of enrollment data is searched by each challenge until either a match is made, indicating an action, possibly dependent upon the specific match, or no match is made indicating an abort. In one application an individual is accepted or rejected as an imposter, in another applicaton, a selected action is accepted as corresponding to a verbal command.