[AG-TECH] multiple mics

[Jeremy W Herr]

Hello All,
	I am new to this list, and as will quickly become apparent, I have
very limited experience with audio equipment.  We in U-M High Energy
Physics are building a *portable* system for recording lectures, including
the speaker's video/audio, slides, and audience questions.  Although we
would like to turn it into a
remote-participation/collaboration/all-purpose-videoconferencing-device
some day, the first attempt will be to passively record the multiple media
streams, with no need for reinforcement (I just learned that word from an
audio expert) or any kind of real-time broadcasting.  So no echo
cancellation is needed, I think.
	My question is about recording multiple audio streams.  We would
like to position multiple mics throughout the audience to pick up audience
questions (at least 2 mics dedicated for this purpose, probably boundary
or PZM mics mounted on plexiglass panels?), but most of the time we would
like these mics to be absolutely silent, giving full preference to the
speaker.  When someone in the audience is asking a question, we would like
to only record the mic closest to them, and auto-adjust the level (because
they might be near the mic or far away from it).
	Does anyone have any suggestions?  I suppose no matter what we do,
the speaker's audio should be captured separately and always on.  For
multiple audience mics, I know of expensive units ($2000+) from PolyCom
(e.g. EF 2280) that can take multiple inputs and do all kinds of stuff,
but I think these units do more than we need to do (like echo
cancellation).  All I want to do is sense which mic is closest to the
speaker and listen to that one.

If anyone has experience in this, I would be grateful for any advice or
general pointers.

Jeremy Herr

________________________________________________________________________
herrj at umich.edu - cern.ch/jherr, www-d0.fnal.gov/~herrj
Computer Systems Consultant II, U-M Physics