On Tue, 30 Oct 2012 10:25:09 -0700, Jeff Liebermann wrote:


Ok, all mechanical and no electronics. Take a large ring with a
diaphragm stretched across the ring. Find a mechanical barometer and
tear it apart. Remove the pressure chamber and connect the actuator
arm to the center of the large drum. Add a bit of fluid damping by
submerging the mechanism in thin oil (5-10wt). When the sound
pressure in the room moves the drum slightly, the barometer mechanism
will indicate the peaks. Patent pending...


Snaps fingers. That's it. Sheer genius!
A single 2" loudspeaker clamped to the back of a barometer.
Speaker cone has a pressure valve fitted.