Hi all. I am out of town until Friday so I won't be able to reply all that much. I work in the area of active noise control for NASA. We concentrate on interior noise in aircraft, and I am currently working on active boundary layer induced noise control.
Anyway I guess my generala comment is to encourage the investigation, but I can say that each active system is taylored to a particular problem, etc. It is by no means easy. People have been working in this area for 15 - 20 years, and there is only a few different type systems available. The active headsets have done very well, and there are some active tonal noise reduction systems for propeller noise in aircraft. These two systems are quite different and require a drastically different controller.
The headset problem is by far the easiest because it is sort of a 1 - D problem. The air cavity formed between the headset and the ear is small so that for a huge frequency range the speaker, and error microphone, and ear drum appear co-located. Being co-located leads to great performance and relatively easy controller (electronics) design. How does this relate to the projector problem? For the projector you need to be able to recreate the noise field produced by the projector using the speakers. Depending upon the frequncy content of the noise and size and shape of the projector this can be quite difficult. You typically have to locate the speakers within 1/4 of a wavelength of the noise source at the highest frequency you want to control. Thus at 1000 Hz the wavelength is ~1 ft and thus the speakers should be within three inches of the noise sources. Thus if there are several areas on the projector radiating noise then you would have to have control sources spaced all over the projector. If you can recreate the noise field with the control speakers then there is a hope that you could get global noise reduction (quieter everywhere). If not you will get local control arround the error microphones. Thus you would want to mount the error microphones on your wifes ears like ear rings and have her hold very still http://www.avsforum.com/ubb/smile.gif http://www.avsforum.com/ubb/smile.gif
If you are lucky enough to be able to obtain global control then the error microphone location is not quite as sensitive, etc. The controller design will be totally dependent on the frequency content of the fans, the phase angles of everything, the geometric location of the noise sources, the control sources, and error microphones. It is etremely unlikely that the controller used in the headset that you have as a doner will work in this system.
I am sorry to rain on the parade, but the problems can be quite difficult. NASA, private companies, and universities have spent propably 100's of millions of dollars studying and developing these systems. I strongly encourage the work. We will all learn a lot from the findings, etc.
DVI/HDCP! ~= HD-DIVX!!!
DO NOT SUPPORT JVC or anyone else who supports this!