Sound Propagation

[Richard Brekne]

John Delacour wrote:

> At 9:16 PM +0100 1/8/02, Richard Brekne wrote:
>
> >This is still in the opening chapters of his book and I still don't
> >have anything to couple this kind of wave propagation directly to
> >the sound board. But if vibration energy has to propagate in similar
> >fashion for all elastic medium...then ...well I am still pointed in
> >that direction. In any case it was neat to see that my thinking
> >along the pond / ripple tangent wasn't completely out in left field.
> >:)
>
> Richard, so long as you go on thinking of waves in ponds and lakes
> and troughs, this discussion will again be drowned in a sea of
> irrelevancies.
>

Gotta like your style John...grin... Like I say, I am working my way
through a lot of this, and if that neccessitates me ...er...
"pondering", as it were a few irrelavancies along the way, well I suppose
thats indicative of how some of us actually learn.  Plus I suppose there
are several, who like me are in that position of having to learng to
dogpaddle before learning to swim. In anycase I see no harm in gaining a
better understanding of all these things, if for no other reason then to
come to understand their limitations.

> The soundboard+ is a solid system with clamped edges.  In so far as
> it exhibits any flexural vibrations, those vibrations will be at the
> natural frequencies of the board and may or may not have some slight
> influence or complicating effect on the propagation and radiation of
> the sound from the strings, but as a complication I'd say it ranks
> exceedingly low among a host of more important complications.

I think you are refereing to what Benade is calling the natural modes of
vibrations. You know, when I picked up Benades book I started looking
through information dealing with reasonators, soundboards, and sound
chambers and found quickly that the understanding the material required
that I start much earlier on in the book to gain a more solid
understanding of the descriptions of more fundemental principals.

> The main function of the soundboard is to propagate sound through its
> own
> anisotropic substance and to radiate acoustic energy at its surface.
> A soundboard is neither a thin pond nor a membrane nor a blanket nor
> a clothes-line.

I dont believe that I have declared with any authority that it is, I have
simply related my own thinking about things as I gain more understanding.
Look at is as sort of a daily diary about where I am in that process at
any given time.
But ok... since you seem to be taking the discussion away from the means
of energy transfer from the strings to the bridge, and moving it towards
how sound emanates from the already exited soundboard. Why dont you
describe your understandings of this in more detail. The phrase "radiate
acoustic energy" for example.... thats a little vague on the surface of
it...

>
> JD




--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no