[Ham-Mac] Noise Canceling Microphones (somewhat off topic)

[David Kelly]

On Jul 12, 2004, at 12:35 PM, K6LMP wrote:

> Second, I found a circuit diagram online for a noise canceling mike
> setup using two RadioShack electret mikes, fed through two small
> and simple transistor amplifiers and with outputs merged 180° out
> of phase. One mike is apparently arranged pointed toward the mouth;
> the other away from the mouth, to pick up ambient noise.  In
> theory, the anbient noise component cancels, leaving only the
> voice.  This was apparently written up in the December 2000 issue
> of QST, which I don't have.  If anyone has experience with this
> setup, I will order a copy of the article from ARRL.

That is how a noise-canceling mic works in the first place. Its 
basically open front and back so that noise which is present from all 
around enters equally from front and back cancels mechanically.

Am not so sure that you couldn't find an electret mic element built to 
be noise-canceling in the first place. Shure and others made entire 
assembled microphones with noise canceling built in, and probably still 
do.

Before buying, double check the requirements of your rig. Not all use 
electret elements.

Let us know what you find. I'm in need of building some inexpensive 
headsets to install in friend's off-road motorcycle helmets to use with 
FRS. "Inexpensive" because if I want them to carry a radio then I have 
to buy and install it. We don't have the same noise problem as 
streetbikes have with wind as we're going slower.

--
David Kelly N4HHE, dkelly at HiWAAY.net
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Whom computers would destroy, they must first drive mad.