To provide a mobile phone with which a hands-free telephone call can be made, without putting on a headset microphone, the mobile phone serving as an audio input interface for a car navigation system.

A plurality of microphones 2 are mounted on the mobile phone 1. Echo canceller processing 4 is performed for an input to suppress a sound repeatedly input from a speaker 3. Before starting a voice operation or telephone call, a user speaks a predetermined word, and then spoken speech detection 5 is performed. When the word is recognized, a mean gain value of a speech signal obtained by the input and the gain value of a noise signal obtained in several seconds after the speaking are calculated. Gain correction processing 6 is performed, based on both the gain values and noise suppression 7, is further carried out to obtain an articulate speech signal. For a telephone call, the voice signal is transmitted and for operations of the car navigation system, a signal, after voice recognition feature quantity conversion 8 is transmitted.

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