[Test-Equipment] HP audio oscillator FS?---guitar testing

[Brian Burns]

Hello Dale,

Thanks for the warning. Fortunately I just need to get enough fundamental
energy into a loudspeaker that I can make poppy seeds assume the Chladni
pattern of a vibrational mode on a guitar---or piece of wood that I'm
testing. Distortion doesn't matter much---within reason!

I have a small horn PA speaker mounted on an extension lamp arm. I move it
around to find a good excitation spot, and with the audio oscillator tuned
to one of a guitar's resonances, the poppy seeds dance around until they
find a node. The pattern they make identifies the mode that has shown up on
a response curve as a resonance peak. 

In the higher treble regions the poppy seed patterns can get pretty mixed
and unclear, so if anybody just happens to have a laser holography setup,
that's just sitting around (;->)...

There are a bunch of standard ways a traditional Spanish guitar vibrates,
and it's where these resonances occur in the audio spectrum that determines
the "voice" of that instrument. 

If anyone is interested, I have .pdf's of illustrated notes that I can email
as attachments. I give them out to my guitar making students who have been
through the process with me, so they are a bit sketchy, but you guys will
have no difficulty understanding them.

Cheers,

Brian


See my website: www.lessonsinlutherie.com

  
At 09:58 AM 12/13/2016, Brian Burns wrote:

>I have a Heath function generator sitting on my "ham bench" ... If it 
>will put out something as mundane as a sine wave at audio frequencies, 
>I will use it for my wood testing and "voicing" processes.

Bear in mind that, depending upon circuit topology, the sine output from a
function generator may have enough distortion to matter in some
applications.

Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcity/radios/index.html 


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