Stress waves (was violin bridge)

[Phillip L Ford]

On Sun, 6 Jan 2002 10:01:56   
 John Delacour wrote:

> Robin's latest post brings us back 
>to the essential starting point, which is the termination of the 
>string at the bridge, where the transfer of energy begins, where the 
>inital stress is set up.  I want to get a clear idea of what happens 
>here.  At the moment I see a molecular disturbance occurring here 
>which radiates into the bridge; and I use the word 'radiate' in a 
>strict sense, in that the pressure waves travel outwards from the 
>source as the rays of the sun or the spokes of a wheel from the hub. 
>These waves travel just as much along the bridge as down through it, 
>though not necessarily with exactly the same speed or amplitude, 
>since various factors will modify these.  Before we even get to the 
>soundboard, there is plenty to consider.
>
>
>JD
>
I haven't read Robin's post yet but I will.  The propogation of stress
waves, compression waves, or sound waves (however you choose to
call them) from the point of contact between string and bridge seems
likely.  However, I don't see why that would prevent the string(s) from
physically moving the bridge and soundboard which would move air
which we would hear.  As I see it both things can be going on at once.
It doesn't have to be either/or.
But I'm still mystified as to how these compression waves get 
transformed into transverse vibration of the soundboard (I think from
what I have read in these posts that everyone is agreed that transverse
vibration of the soundboard has to take place to move air so that we can
hear the sound).  Why wouldn't the compression wave remain a compression
wave?  Why wouldn't it travel through the bridge, into the board, to the rim
and back all the while remaining a compression wave?
I've ordered a couple of books on wave propagation.  I'll see what the
people who are supposed to be authorities have to say on the subject.

Phil F