I imagine if you are doing this for a Uni project, then it will be getting the principles right, rather than making something that is 100% reliable. I have never built voice recognition circuits myself, but I imagine it would be very difficult designing your own. I reckon Audiogurus suggestion was pretty good. If you could design something similar to a VU meter on a Hi-fi, then have it triggering at a set Voltage. You could use a LM3915 and have one of the higher level outputs as the trigger. I'm not sure if this is the right advice, as I am only a beginner (someone please tell me if I am wrong!!!)
Take a look here:
**broken link removed**
By the way. If you are just turning a tube light on and off, why not just have it triggering on one syllable for both on and off. You can't turn a light on, and then turn it on again without turning it off can you? Unless you are doing anything more complexed, I don't see why you can't do something similar to one of those "clap" lights where you clap your hands to turn it on, and then clap them again to turn it off.
Sorry if my ideas are stupid. I'm still learning,
Kind regards,
Mike