To suppress Doppler distortion, caused by a loudspeaker, included in a sound generated in a loudspeaker obtained by combining an amplifier and the loudspeaker.

With respect to a sound signal after volume processing, a differentiation signal which becomes a time differentiation of the sound signal and an integration signal which becomes a time integration of the sound signal are calculated and a signal in proportion to a product of the differentiation signal and the integration signal is subtracted from the original sound signal. A signal as a result of the subtraction is amplified by an amplifier and a loudspeaker is driven, thereby obtaining a sound from which Doppler distortion caused by the loudspeaker has been canceled.