9. The method as described in claim 7 , further comprising outputting a predetermined voice signal if the similar voice texts exist neither in the base voice database and the extension voice database.
7. The method as described in claim 6 , wherein the at least one voice database comprises a base voice database and a extension voice database, the base voice database stores a plurality of predetermined voice texts and a plurality of answer texts each associated with one of the predetermined voice texts, the predetermined voice texts are texts converted from predetermined voice signals, the answer texts are texts converted from predetermined answer voice signals corresponding to the predetermined voice signals, the extension voice database stores a plurality of extension voice texts which are texts converted from the voice signals input by the user and a plurality of answer texts which are answer texts corresponding to one of the extension voice texts.