1. A method for accelerating neural network execution in a speech-recognition system, for recognizing words contained in a subset of a general vocabulary of words that the same system is capable of recognizing, said neural network comprising a number of computing units organized in levels including at least one hidden level and one output level, the computing units of said hidden level being connected to the computing units of said output level via weighted connections, said computing units of said output level corresponding to acoustic-phonetic units of said general vocabulary, said acoustic-phonetic units comprising stationary units and transition units, the method comprising the following steps: determining a subset of the acoustic-phonetic units to always include all of said stationary units and only include those of said transition units that are necessary for recognizing all the words contained in said general vocabulary subset; eliminating from the neural network all the weighted connections afferent to computing units of said output level that correspond to acoustic-phonetic units not contained in said previously determined subset of said acoustic-phonetic units, thus obtaining a compacted neural network; and executing, at each moment in time, only said compacted neural network.