1. A processing unit that executes processing for speech recognition, said processing unit comprising: a processor programmed to comprise: an initial reflection component extraction portion that extracts initial reflection components by removing diffuse reverberation components from a reverberation pattern of an impulse response generated in an environment; an acoustic model learning portion that learns an acoustic model for the speech recognition by reflecting the initial reflection components to speech data for learning; a diffuse reverberation component extraction portion that extracts an approximated diffuse reverberation components from the reverberation pattern of the impulse response generated in the environment; and a filter creation portion that creates a filter parameter for every input speech for subtracting approximated spectrum components of the diffuse reverberation components.