1. A computer implemented method for efficient empirical determination, computation, and use of an acoustic confusability measure, comprising the steps of: empirically deriving an acoustic confusability measure by determining acoustic confusability between at least any two textual phrases in a given language; wherein said measure of acoustic confusability is empirically derived from examples of application of utterances to a specific speech recognition application; iterating from an initial estimate of said acoustic confusability measure to improve said measure; and using said acoustic confusability measure to make principled choices about which specific phrases to make recognizable by said speech recognition application.