16. The prosody generating method according to claim 14 , wherein the prosody information includes a time change of a fundamental frequency as a feature quantity representative of prosody.
14. A prosody generating method, implemented by a processor, the method comprising: dividing into subspaces the data space of a learning database as an assembly of learning data indicative of feature quantities of speech waveforms; extracting density information indicative of a density state in terms of information quantity of the learning data in each of the subspaces obtained by the division selecting either a first method or a second method as a prosody information generating method based on the density information, the first method involving generating the prosody information using a statistical technique, the second method involving generating the prosody information using rules based on heuristics; in the selecting either the first method or the second method, selecting the second method when the density information indicates the density state is sparse; and outputting a generated synthetic speech based on the prosody information.