14. A computer program product comprising a non-transitory processor-readable storage medium having encoded therein executable code of one or more software programs, wherein the one or more software programs when executed by the at least one processor implement the steps of: converting a non-back-off language model to a back-off language model using a background language model, wherein the non-back-off language model assigns a probability to any fixed order n-gram without backing off to lower order n-gram probabilities, and wherein the background language model assigns a non-zero probability to n-grams assigned a zero probability by the non-back-off language model; and pruning the converted back-off language model; wherein the converted back-off language model assigns a probability to a given fixed order n-gram assigned a zero probability by the non-back-off language model and not assigned a fixed order probability by the background language model by backing off to a given lower order n-gram corresponding to the given fixed order n-gram; wherein the given fixed order n-gram comprises a given word and an associated history; wherein the given lower order n-gram comprises the given word and a truncated version of the associated history; wherein lower order n-grams originate from at least one lower order non-back-off language model after converting the lower order non-back-off language model to the back-off language model and highest order n-grams originate from an n-gram language model; and wherein the converted back-off language model is usable for decoding speech via at least one speech decoder associated with an automatic speech recognition system configured to integrate the converted back-off language model into a decoding process.
16. The computer program product of claim 14 , wherein the non-back-off language model comprises a plurality of non-back-off estimates and the back-off language model comprises a plurality of back-off estimates and a plurality of non-back-off estimates.