Hitachi Denshi Kabushiki Kaisha

Yasushi Kudo

Yoshiro Kokuryo

A speech signal bandwidth compression and expansion apparatus and its method. On the transmitting side, system parameters are extracted from a speech signal by a linear prediction analyzer. A prediction residual signal is obtained by inverse filtering processing by using the system parameters. The prediction residual signal is lowered in sampling rate by a down-sampler and converted to a baseband signal. From the baseband signal, a time series signal is derived by a linear prediction synthesizer. Thereafter, the time series signal is converted to an analog signal and transmitted. On the receiving side, a received signal is subjected to inverse filtering processing to reproduce a baseband signal. The sampling rate of the reproduced baseband signal is raised to derive a time series signal. From the time series signal, a high frequency band component is generated. The high frequency band component is added to the baseband signal to generate an excitation signal. From the excitation signal, the original speech signal is reproduced by a linear prediction synthesizer.

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Kamakura, Japan

Yasushi Kudo