2. The specific call detecting device according to claim 1 , wherein the voice recognition execution determining unit 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.
2. The specific call detecting device according to claim 1 , wherein the voice recognition execution determining unit 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. 7. The specific call detecting device according to claim 2 , further comprising: a psychological state determining unit which determines whether a psychological state of the first speaker is normal or not on the basis of the first voice; and a storage unit which stores, as the keywords, a first keyword having the number of syllabic sounds equal to or larger than predetermined number of syllabic sounds and a second keyword having the number of syllabic sounds less than the predetermined number of syllabic sounds, wherein the voice recognizing unit detects the first keyword from voice determined as a target of the voice recognition when it is determined that the psychological state of the first speaker is normal and, on the other hand, detects the first and second keywords from voice determined as a target of the voice recognition when it is determined that the psychological state of the first speaker is not normal.