Patent ID: 7318034

Claim:
A voice signal interpolation apparatus comprising: pitch waveform signal generating means for acquiring an input voice signal representative of a waveform of voice and making a time length of a section corresponding to a unit pitch of said input voice signal be substantially the same to transform said input voice signal into a pitch waveform signal; wherein said pitch waveform signal generating means comprises: a variable filter whose frequency characteristics can be controlled to be variable, said variable filter filtering said input voice signal to derive a fundamental frequency component of the input voice; filter characteristic determining means for identifying a fundamental frequency of the input voice in accordance with the fundamental frequency component derived by said variable filter and controlling said variable filter so as to have the frequency characteristics cutting off frequency components other than frequency components near the identified fundamental frequency; wherein said filter characteristic determining means comprises: cross detecting means for identifying a period of timings at which the fundamental frequency components derived by said variable filter reach a predetermined value and identifying the fundamental frequency in accordance with the identified period; average pitch detecting means for detecting a time length of a pitch of voice represented by said input voice signal in accordance with said input voice signal before being filtered; and judging means for judging whether the period identified by said cross detecting means and the time length of the pitch identified by said average pitch detecting means are different from each other by a predetermined amount or more, if it is judged that the period and the time length are not different, controlling said variable filter so as to have the frequency characteristics cutting off frequency components other than frequency components near the fundamental frequency identified by said cross detecting means, and if it is judged that the period and the time length are different, controlling said variable filter so as to have the frequency characteristics cutting off frequency components other than frequency components near a fundamental frequency identified from the time length of the pitch identified by said average pitch detecting means.