impedance for 99

[Doug Richards]

Jory,
GEARHEAD?
OUCH!!!

On the Laser interferometers, usually the output is velocity. And yes, the
HP thingy's are setup to do this very well.

UPDATE:  Soundboard shape with ribs and bridge have now been imported into
ANSYS.  Now the modeling fun really begins...

Question1:  For simplicity the first cut at a soundboard will have no crown
and be one thickness.  What would any of you estimate for an average
soundboard thickness and rib thickness?  Numbers only please, no sermons!
This is a very simplified model.

Question2:  What would you estimate the soundboard grain direction is
relative to the ribs?

doug

> -----Original Message-----
> From:	Jory A. Olson [SMTP:jory@teleport.com]
> Sent:	Friday, January 01, 1999 11:07 PM
> To:	'pianotech@ptg.org'
> Subject:	RE: impedance for 99
> 
> I promised I would be good and not post unless I had something really
> important to say.  That time has come....
> 
> I must say that I find this discussion soundboard impedance to be
> fascinating.  As an electrical engineer I'm comfortable with the idea of
> soundboard impedance.  I even think it wouldn't be that hard to measure
> mechanical impedance.  If voltage is analogous to force and current is
> analogous to velocity (not of the wave but of the displacement from the
> force) if should be possible to mount a linear motor (like the motor from
> a speaker) to the soundboard and measure the displacement with a laser
> interferometer.  The first time derivative of displacement is velocity.
> One could then calculate both the real and imaginary parts of the
> impedance by "doing the math".  It's ohms law for soundboards!  That would
> be something like:  Force/Velocity = Impedance  The tricky part would be
> getting the timing of the force and the measurement of the displacement to
> be synchronous.  I'd be shocked if one of those HP Fourier Analysis
> thingy's the gearheads (mechanical engineers) are always using!
> !
> !
	...
> Jory