14. The specific call detecting method according to claim 13 , wherein the determining whether at least one of the first and second voices is to be a target of voice recognition or not, determines that the first voice is a target of voice recognition until a period in which the utterance ratio is higher than a predetermined threshold, reaches a first period, and determines that the first voice is not a target of voice recognition after the period in which the utterance ratio is higher than the threshold, reaches the first period.
14. The specific call detecting method according to claim 13 , wherein the determining whether at least one of the first and second voices is to be a target of voice recognition or not, determines that the first voice is a target of voice recognition until a period in which the utterance ratio is higher than a predetermined threshold, reaches a first period, and determines that the first voice is not a target of voice recognition after the period in which the utterance ratio is higher than the threshold, reaches the first period. 16. The specific call detecting method according to claim 14 , further comprising determining whether a psychological state of the first speaker is normal or not on the basis of the first voice, wherein the determining whether at least one of the first and second voices is to be a target of voice recognition or not, sets value of the threshold when it is determined that the psychological state of the first speaker is not normal to be larger than value of the threshold when it is determined that the psychological state of the first speaker is normal.