Patent ID: 8280727

Claim:
A voice band expansion device comprising: a time-frequency converter that calculates, using a processor, a frequency spectrum of a voice signal having a first frequency band, by performing time-frequency conversion on the voice signal every frame having a predetermined time length; a separator that extracts, from the frequency spectrum, an envelope amplitude spectrum of the frequency spectrum, a periodic amplitude spectrum whose spectrum intensity periodically changes in response to frequency, and a random amplitude spectrum whose spectrum intensity randomly changes in response to frequency; an envelope amplitude spectrum band expander that expands a frequency band of the envelope amplitude spectrum to a second frequency band that is different from the first frequency band; a periodic amplitude spectrum band expander that expands a frequency band of the periodic amplitude spectrum to the second frequency band; a random amplitude spectrum band expander that expands a frequency band of the random amplitude spectrum to the second frequency band; a broadband spectrum calculator that calculates a broadband frequency spectrum having the first frequency band and the second frequency band, by combining the band-expanded envelope amplitude spectrum, the band-expanded periodic amplitude spectrum, and the band-expanded random amplitude spectrum; and a frequency-time converter that generates a voice signal having the first frequency band and the second frequency band, by performing frequency-time conversion on the broadband frequency spectrum.