Advanced Controls for Microphone

[Rich]

In the "Advanced Controls for Microphone" dialog, under Adjust Audio
Properties | Voice | Voice Recording | Microphone Volume | Advanced, there
is a checkable box for something called "1 MIC Boost." Can someone tell me
what that does, and if it should normally be checked?

I'd also appreciate any advice on at what level the normal Microphone volume
should be set, for things like recording phone message greetings and the
like. I can't seem to get it just right; either the recording is too low,
with audible background noise, or audible "clipping" if I jack up the
recording volume.

Thanks in advance for any advice,
Rich