1. A method for authenticating users comprising: calculating signal features for an audio digital signal representing a user utterance, the signal features including onset values, the onset values correspond to stress accents in the signal; splitting, by a processor, the signal into a prosodic unit candidate sequence based on the stress accent locations; modifying, by the processor, the prosodic unit candidate sequence based on the signal features, the modified prosodic unit sequence including only true prosodic units calculating a first probability that the true prosodic units match a prosodic unit sequence used to create a hidden Markov model for the user; calculating a second probability that the true prosodic units match prosodic unit sequences used to create a Universal Background Model; and successfully authenticating the user when the difference between the first probability and the second probability is greater than a decision threshold.