1. An information extraction apparatus comprising: input signal dividing means for dividing an input signal into predetermined regions; amplitude-value computation means for computing an amplitude value of said input signal divided by said input signal dividing means; analysis region setting means for setting an analysis region on the basis of said amplitude value computed by said amplitude-value computation means; waveform information extraction means for extracting waveform information of said input signal of said analysis region set by said analysis region setting means; synthesized waveform generation means for generating a synthesized waveform on the basis of said waveform information extracted by said waveform information extraction means; and residual signal generation means for generating a residual signal on the basis of said input signal divided by said input signal dividing means and said synthesized waveform generated by said synthesized waveform generation means.