1. A translation apparatus that integrates both phrase-based and free-form speech-to-speech translation approaches using probability models, comprising: a housing; a first communication member embedded in the housing, the first communication member configured to receive vocal communication from a user speaking in a source language; an input audio buffer operably connected to the first communication member, the input audio buffer configured to store the vocal communication transferred from the first communication member; a speech recognition module configured to recognize a plurality of preset phrases and a plurality of free-form phrases, the speech recognition module further configured to receive the vocal communication from the input audio buffer and decipher the content of the vocal communication; a multilingual dictionary module operably connected to the speech recognition module, the multilingual dictionary module configured to locate a corresponding translation of the vocal communication provided a preset phrase exists in the speech recognition module for the vocal communication; a translation module operably connected to the speech recognition module, the translation module configured to translate the vocal communication into the target language; a synthesis module operably connected to the translation module, the synthesis module configured to synthesize text to speech (TTS) for the translated target language; an output audio buffer operably connected to the multilingual dictionary module and the synthesis module, the output audio buffer configured to store prerecorded speech sounds from the multilingual dictionary module corresponding to the translated vocal communication and further configured to store the synthesized speech sounds from the synthesis module corresponding to the translated target language; a second communication member embedded in the housing and operably connected to the output audio buffer, the second communication member configured to receive and play the stored sounds in the output audio buffer; and a selection switch embedded in the housing for allowing the user to selectively choose between either one of the phrase-based approach and the free-form approach of speech-to-speech translation; wherein the TTS synthesis occurs for at least one of, (i) free-form TTS for handling text and (ii) phrase-based large inventory pre-recorded sentences and phrases.
2. The apparatus of claim 1 , wherein the speech recognition module configured to decipher the form of the vocal communication yields the best recognition output when ŵ=arg w max p(X|W, λ w ), where λ W is the probability weight for a given text W and 1≧λ w ≧0, wherein ŵ is the recognition result and X represents the input speech signal.