On Fri, 18 Jun 2004 17:09:56 GMT, Chris Hornbeck
wrote:

There are two useful choices for the mass/ compliance resonance,
above and below the passband. The usual choice for open (pressure-
differential sensitive) microphones is below passband and the usual
choice for closed (pressure sensitive) microphones is above
passband.

This is so poorly worded that I can't let it drop. Imagine a
loudspeaker woofer in a sealed box and driven by a constant
RMS voltage at all frequencies.

If we measure its sound pressure output, we see it rise at
12 dB/ octave from very low frequencies up to its resonant
frequency, where pressure response levels off to flat.

If we measure its diaphragm excursion, we see that it's flat
from low frequencies up to resonance, then it falls at 12 dB/
octave.

There are two components to the diaphragm excursion. The
diaphragm's velocity increases at 6 dB/ octave up to resonance,
then decreases at 6 dB/ octave above resonance. And
wavelength, which falls continuously at 6 dB/ octave.

Microphones are also four terminal devices designed to
translate voltage and pressure. All the same rules apply.
To make non-equalized microphones with flat pressure input vs.
voltage output some strategies emerge:

If our electrical generating mechanism has a flat relation of
excursion to voltage, we simply operate below resonance.

If our generator is velocity sensitive, then our output will
rise at 6 dB/ octave below resonance and fall at 6 dB/ octave
above resonance. Above resonance this is useful with open
diaphragms ("pressure-gradient microphones") whose diaphragm
excursion increases at 6 dB/ octave in their major working
frequency range.

Now I promise the shut the heck up.

Chris Hornbeck