This invention provides a signal processing apparatus for effectively detecting an abrupt change in an input signal. The signal processing apparatus includes a converter that converts an input signal into a phase component signal and an amplitude component signal in a frequency domain. The signal processing apparatus further includes a calculator that calculates feature amounts of the phase component signal and the amplitude component signal derived by the converter. The signal processing apparatus further includes a determiner that determines presence probability of an abrupt change in the input signal based on the feature amounts calculated by the calculator.
