Quasi-periodicity and non-periodicity signal models are proposed. Each hypothetical one-quasiperiodical signal segment is considered as a random distortion of previous or following one taken with the unknown multiplying factor. The problem of optimal current pitch period discrimination and speech signal partition into one-quasiperiodical microsegments consists in the finding of the best onequasiperiod beginnings or the one-quasiperiodical segments under restrictions on both value and changing of current quasiperiod duration and multiplying factor. For this problem solving an effective algorithm based on dynamic programming is proposed and its application for speech signal analysis, recognition and synthesis is discussed.