<< i would expect a six db improvement in self noise when a capsule is
used in the boundary layer.
<Wouldn't the self-noise percentage in the mic's signal be raised
along with the increased output from the boundary effect?>
<no. the gain is noisefree. and first time you hear it, very
impressive. (i have
built many varients on the boundary layer principle.)
umashankar>>
Note that the 'gain' is actually an increase in the acoustic volume at
the surface of the boundary, hence the name Pressure Zone Microphone
of the original commercial implementation of this principal. So the
microphone simply has a louder acoustic signal presented when the
diaphragm is in the pressure zone. Thus less preamp gain is required,
& less gain means lower noise in the resulting recording, even though
the self noise of the system stays the same. I seem to recall that the
pressure zone is about a quarter inch deep in the audible band.
Scott Fraser
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