Sound waves(a neat experiment)

[Ron Nossaman]

>Ron,,, I took the up and down motion out of the picture by not letting it 
>come in
>contact with the wood. 
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>The only thing new in this is the realization that the energy
>coming out the end apparently is stronger then the energy coming out the
sides,
>which is neat to know..... Perhaps because there are two waves fronts coming 
>out of
>the side for every one coming out the bottom ?

Here's where you dismissed the fork action. Where in the world does this
notion that energy leaks out the bottom of something without disturbing the
something come from? Especially since the energy is applied by moving mass.
Like the bridge, you aren't talking about waves leaking out the end here,
the entire fork moves. As the tines oscillate back and forth, they bend to
do so. Because they bend and deviate from being parallel to the length axis
of the fork, the overall length of the fork CHANGES as the tines vibrate.
The center of mass of the fork moves up and down with each cycle, which
means that the fork moves in space. The handle is physically moving up and
down. The entire handle. That includes the sides of the handle as well as
the bottom, which is why you eliminated nothing whatsoever by leaving the
bottom of the fork handle open in your demo. The fork is still pistonically
driving the board transversely. It's very simple and straightforward. There
is some side to side movement of the handle too, but that's the result of
the virtual physical impossibility of exactly matching the length, mass,
and spring rate of the two tines.

That is also why the sound produced by the fork on the tabletop is loudest
from the end of the handle, if you tried the experiment I asked you to.

These are simple straightforward movements we're talking about here and in
the string, bridge, and soundboard, not radiating energy effects that
magically produce movement. It's actual physical movement. That's the
orientation part - basic physical reality.


>Actually, I think its time we all made a concerted effort to leave High School
>physics behind as much and as quickly as possible.

I obviously disagree, since a very large portion of extremely elementary
established physics is being ignored altogether in this whole discussion of
soundboards, sound, waves, etc. An "education" or specific explanation that
doesn't correspond to observable and demonstrable fact is worse than
useless. That's supposed to be what scientific method is about, or am I
wrong there too?



>My table top experiment is incomplete. I have to verify that with an open 
>air mic
>and a contact mic. And I don't think the forks action was really the point
with
>that one as the significant difference I pointed to was that of the case of
>listening to the open air sound, vs isolating (as best I could) the sound 
>internal
>to the wood.

Again discounting the fork motion from your conception of energy flow. When
something doesn't fit, take a step back and question your premise instead
of going deeper into ever more confusing layers of minutiae. It isn't
necessarily a matter of obtaining more education. You probably already
"know" too much that you haven't integrated into the physical world in any
meaningful way. That's why I asked you to think about it instead of looking
up something to think for you. 



>As I used the butt end of the fork in all cases in the table top experiment, 
>the
>basic action and energy should be more or less  constant. The difference in 
>volume
>produced by the countertop seems obviously related to the wood orientation 
>itself,
>though I will be a bit confused methinks if after putting a contact mic I 
>find that
>there is very little difference in the amplitude when the fork is placed
on the
>side of the counter vs the top.  Why THAT should result in a different 
>relationship
>then listening open air will require some explanation I don't have at the 
>moment.
>But I have to verify those results first.

Of course the sound will be different from the edge of the tabletop than
from the top. That's why the experiment I asked you to do was all done on
exactly the same spot on the top of the table. Once with the end of the
fork handle, and twice with the side of the handle lying flat on the
tabletop. Have you tried this?
 

Ron N