Patent ID: 8396703

Claim:
A voice band expander for expanding a frequency band of an input voice signal with a frequency spectrum limited to frequencies below an upper limit, the voice band expander comprising: a reduced signal generator for generating, from the input voice signal, a reduced signal with a modified frequency spectrum in which magnitudes of the frequencies in the entire frequency spectrum of the input voice signal are reduced; a band expanding signal generator for generating, from the reduced signal, a band expanding signal having a frequency spectrum in a band higher than the upper limit of the limited band of the input voice signal; and a band expanded signal generator for combining the input voice signal and the band expanding signal, thereby to form a band expanded signal with an expanded frequency band, wherein the reduced signal generator reduces the frequency spectral envelope and the harmonic structure of the input voice signal, the reduced signal generator comprising: a linear predictive coding (LPC) analyzer for carrying out an LPC analysis of the input voice signal; an LPC filter for reducing the frequency spectral envelope of the input voice signal by using LPC coefficients obtained by the LPC analyzer; a pitch analyzer, responsive to the output of the LPC filter, for determining a pitch and pitch intensity of the input voice signal; and a pitch filter for reducing the harmonic structure of the input voice signal according to the pitch and pitch intensity obtained by the pitch analyzer.