A couple of things that I learned while trying to teach Hal to listen. Almost any background noise will and can hamper Hals ability to recognize words, and by that I mean even the hiss of my air conditioner comming on caused problems. You also need a good microphone and hopefully one that does not pick up your breathing while talking. One last thing is to speak slowly and distinctly while traing. After Hal learns how you pronounce words then you can talk at a normal rate and expect it to understand you a whole lot better.
Bill