10. Speech recognition method of claim 9 , wherein simple acoustic speech models and/or restricted word production rules are applied for the plurality of speech recognition engines, and once only one speech recognition engine is alive after pruning, more complex acoustic speech models and/or word production rules are applied to the remaining speech recognition engine.
9. Speech recognition method of claim 1 , wherein each speech recognition engine uses a set of acoustic speech models, in particular HMMs, and word production rules for restricting allowed words for recognition of the input speech.