A method of selectively performing signal processing in a first mode and in a second mode. In the first mode, a noise cancel signal having a signal characteristic to cancel an external noise component is generated based on a voice signal supplied from a microphone, and an input digital audio signal and the noise cancel signal are combined into a voice signal to be output through a speaker. In the second mode, a sound process for vocal voice is performed on a voice signal supplied from a microphone, a vocal voice component is canceled from a digital audio signal of input music to generate a karaoke signal, and the karaoke signal and the vocal signal are combined into a voice signal to be output through a speaker. The first mode corresponds to an audio replay operation accompanied by noise cancel, and the second mode corresponds to a karaoke operation.