1. A speech recognition method comprising the steps of: (a) receiving input speech from a user via a microphone associated with an automatic speech recognition system; (b) processing the input speech using a first grammar to obtain parameter values of a first N-best list of vocabulary using at least one processor associated with the automatic speech recognition system; (c) comparing at least one parameter value of a top result of the first N-best list to at least one predetermined threshold value; and (d) subsequently processing the input speech using a second grammar to obtain parameter values of a second N-best list of vocabulary, if the compared at least one parameter value is below the at least one predetermined threshold value; (e) determining the input speech to be in-vocabulary, if any of the results of the first N-best list is also present within the second N-best list, but out-of vocabulary if any of the results of the first N-best list is not within the second N-best list; and (f) providing audible feedback to the user if the input speech is determined to be out-of-vocabulary.