> > > Does a product currently exist on the market that:
> > > Takes two or more microphone inputs and applies noise canceling to
> > > them, then provides a noise-suppressed output?

What they all said +

The issue, which Peter alluded to an aspect of, is that you have to
effectively model the space in which the sound is being generated and
monitored. Your canceller does effectively do phase inversion as you
suggest BUT the amplitude and phase of all frequency components
depends critically on the overall environment. International telephone
circuit echo cancellers do this but they have the advantage that their
environment typically contains a boring old cable with some impedance
bumps in it, rather than an auditorium of unknown size and shaped\e,
many audio paths (direct plus reflections) all of which have differing
frequency/amplitude/phase characteristics. Add people, chairs and
tables, opening and shutting doors etc and you need very capable
adaptation software. Simplistically this can probably be modelled as
an IIR filter with variable dynamic taps - telephone cables can, but
they are simpler as noted.
The computer doesn't have to know about its environment - just be
capable of handling the results.

Some very very capable people have worked on all aspects of this
general problem for a long while (eg I know a man who had worked out a
canceller about 35 years ago but had to wait a decade or more while
the available hardware caught up with his ideas).

So, yes, it can be done and it is done, but you are in for some
serious maths if you want to compete with the leaders.

               R
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.