"John T" wrote in message
...
What makes a quality microphone in a headset? somethat that doesn't pick
up the cockpit noise, but still transmits your voice clearly?

I've got a project in mind that would require such a microphone. I
thought of using the parts from a reconditioned headset, but I'd like to
get some opinions/options.

Presuming that the question is general theory, you are primarily looking for
a headset with a noise canceling mic.

Classically, a noise cancellig mic is two microphones placed either back to
back or a radically different distances from the mouth of the person
speaking. For example, a mic pickup placed one inch from the speakers
mouth, and the second at three inches, so that the evels are radically
different. The two microphones are then wired out of phase, so that the
background noise, which is assumed to reach both microphones equally, will
be cancelled. In addition, sound outside the classic "telephone" band of
300Hz to 2500Hz can be filtered out for a further benefit in
intelligibility.

The low-tech solution above works amazingly well in a large open area,
especially outdoors, and also works well with a noise cancelling hand held
mike when held closely; but has serious limitations in an aircraft cockpit,
especially if the mic boom is not long enough to provide good proximity.

I understand that some of the newer earpeices include a microphone to pick
up a pilots voice, presumably by bone conduction, and include sufficient
filtering to restore a reasomable range of frequencies. In addition, some
of the newer microprocessor based filters may provide far better noise
cancelling than the older methods. However, I have been out of the avionics
industry for nearly twenty years, and have no experience with either of the
last two methods.

I hope this helps.
Peter