Sound waves(The behavior of soundboards)

[John Delacour]

At 11:37 AM -0600 12/16/01, Ron Nossaman wrote:
>  >When I walked away from this topic, having proposed such a test and
>>had it arbitrarily dismissed, in my own mind I had hardly travelled
>>beyond the point at which the string meets the bridge, though others
>>were anxious to generalize and get by any means to talk of the
>>rippling soundboard.  I can't myself make such a leap of faith, so I
>>would like to return to this meeting-point.
>
>And that's the problem when a discussion is immediately dragged in fifteen
>different directions at once, isn't it?.....Just drive a few wedges between
>the bracing and a few points under the bridge and see if there is any
>noticeable difference in produced sound......

You're doing it again!

At 7:09 PM -0800 12/3/01, Delwin D Fandrich wrote:
>Is this a serious question?....There was still some sound there, but 
>it was muted
>and thin.
>
>...The bridge movement moves the soundboard causing it to vibrate 
>much like the
>diaphragm vibrates in the loudspeaker.


At 7:25 PM -0600 12/3/01, Ron Nossaman wrote:
>  > but you suggest the effect will be to kill the bass of the piano as though
>  >the soundboard and bridge were not there, since the loudspeaker effect of
>  >the soundboard depends on the solenoid effect of the bridge.
>
>That should be the case. Just like clamping the driving coil of a speaker
>cone to the magnet. The transducer can't transduce if it can't move.

So way back then you said it "should be the case", according to your 
theories that immobilizing the bridge should prevent any vibrations 
reaching the soundboard, and Del states categorically that the bridge 
moves and acts as a speaker solenoid BUT that there was a muted and 
thin sound.  I have never suggested that the immobilizing of the 
bridge will have NO effect on the sound.  My point has always been 
that a good deal more sound will be audible when the bridge is 
immobilized than would be heard from the string and bridge alone, 
that this sound is emitted from the soundboard and has reached it NOT 
as a result of the "solenoid effect".  If the solenoid of a speaker 
is jammed, no sound at all will be emitted from the cone.  The two 
cases are completely different.

In my most recent message, I have not involved the soundboard.  In 
the picture I have painted so far, I have made no mention of the 
soundboard except in my last paragraph as a trailer to the next 
episode:

At 3:43 PM +0000 12/16/01, John Delacour wrote:
>It is the oscillation of the molecules next to the glue line, 
>excited by kicks and shoves from all directions within the bridge, 
>that will now raise a rumpus in the soundboard.  The bridge so far 
>remains unmoved, its internal tranquility severely disturbed but 
>outwardly unmoved, unrippled, unfurrowed.

You write:

>I see a string ...physically moving the bridge, which physically 
>moves the soundboard, which physically moves the bridge, which 
>physically moves all of the strings in the system.

And there is the profound difference between us.  I do NOT see a 
string physically moving and rocking a bridge and driving the board 
as a solenoid drives a cardboard cone.  I contested the analogy from 
the very beginning and do so now.

Did I ever say the soundboard does not move?  That would indeed be an 
odd statement. Did I ever say the bridge does not move?  Since the 
bridge is glued and screwed to a flexing soundboard, that would also 
have been a pretty tricky position to maintain.  I said neither.

What I do suggest is that nothing moves at all until those vibrations 
or molecular disturbances or compression waves cross the glue line 
into the soundboard.  At that moment, things get a-movin' an 
a-shakin'.

JD