19. A non-transitory computer readable medium that readably records in a computer a language model score look-ahead value imparting program to cause the computer including a memory unit storing a word dictionary to define a phoneme string of a word and a language model to impart a score of appearance easiness of a word to execute a process of: obtaining a language model score look-ahead value at each phoneme in the word from the phoneme string of the word defined by the word dictionary and the score defined by the language model; preventing the language model score look-ahead values from concentrating on the beginning of the word by distributing the language model score look-ahead value corresponding to the phoneme at the beginning of the word to one or more phoneme that are not at the beginning of the word; and obtaining an updated language model score look-ahead value at each of the phoneme based on the distribution.
19. A non-transitory computer readable medium that readably records in a computer a language model score look-ahead value imparting program to cause the computer including a memory unit storing a word dictionary to define a phoneme string of a word and a language model to impart a score of appearance easiness of a word to execute a process of: obtaining a language model score look-ahead value at each phoneme in the word from the phoneme string of the word defined by the word dictionary and the score defined by the language model; preventing the language model score look-ahead values from concentrating on the beginning of the word by distributing the language model score look-ahead value corresponding to the phoneme at the beginning of the word to one or more phoneme that are not at the beginning of the word; and obtaining an updated language model score look-ahead value at each of the phoneme based on the distribution. 27. A non-transitory computer readable medium that records in a computer, in a computer-readable way, a speech recognition program to cause the computer to execute a speech recognition process that performs frame synchronous beam search using a language model score look-ahead value obtained by a language model score look-ahead value imparting program recorded in the program storage medium according to claim 19 .