1. A speech translation system comprising a control device, two or more speech recognition apparatuses, two or more translation apparatuses, and two or more speech synthesis apparatuses, Wherein the control device comprises: a speech recognition requesting unit, which requests a speech recognition process from each of the two or more speech recognition apparatuses at the beginning of a conversation; a speech recognition processing result receiving unit, which receives two or more speech recognition processing results each including a speech recognition result and a speech recognition score from the two or more speech recognition apparatuses; a speech recognition result selection unit which selects a speech recognition result that corresponds to the highest speech recognition score; a speech recognition apparatus selection unit, which selects the speech recognition apparatus that produced the selected speech recognition result, and directs the speech recognition requesting unit to use only the selected speech recognition apparatus thereafter; wherein the control device further comprises a counter, which counts the number of utterances processed by the speech recognition apparatus, wherein if the highest score meets or exceeds a predetermined threshold, the selected speech recognition apparatus is selected for all further speech recognition processing, and if the highest score does not meet the predetermined threshold, the control unit tracks the number of times the speech recognition process has run, receives subsequent speech recognition scores from each speech recognition apparatus, and averages those scores with prior speech recognition scores, compares the average scores to the threshold, and selects the speech recognition apparatus with the highest average score for further processing, wherein if at any time in the conversation the average score for a speech recognition apparatus meets or exceeds the threshold, that apparatus is selected for all further processing.