Violin bridges

[John Delacour]

At 8:49 AM +0000 1/5/02, Phillip L Ford wrote:

>Actually I think that a violin bridge is more illustrative of Ron's 
>position than your own.  If the violin top is being activated by 
>compression waves...

There's no *if* about it.  Sound is propagated in the same way 
thoughout the cosmos.  Of Ron's 'position'  (that "bodily movements 
of the bridge cause the soundboard to move and to produce the sound 
of the string into the air") I will merely echo Robin in saying it is 
"fantastic ... to think such could explain the energy transfer 
between string and bridge/soundboard".

>  then what difference would it make what the bridge looked like? It 
>could just be a solid piece.

Download <http://www.maestronet.com/m_library/violinist/19270305.pdf>

>   The bow is moving the string side to side. The top needs to move 
>up and down to move the air so that we can hear the violin.  So 
>violin makers have cleverly devised a bridge and soundpost system to 
>convert the side to side motion of the string to up and down motion 
>of the top.

Nonsense.  The flexibility and mass of the system is concerned with 
its acoustic impedance, just as in a piano.  It is not "up and down 
motion" of the plate that radiates the sound any more than it is in 
the piano.

>   The bridge is rocking about the one foot that is over the 
>soundpost which is causing the other foot to move up and down. 
>Apparently violin makers seem to feel that some physical movement of 
>the top needs to take place as a result of the string movement.  I 
>believe the cuts or incisions are not there to 'lengthen the path of 
>the sound' (I'm not sure what the purpose of that would be anyway)

Read the above URI.  What people 'seem' to do and what people 
'believe' have no place in a serious discussion.

>  but to cause the flexibility (or impedance if you like) of the 
>bridge to be more or less the same for the four strings, since two 
>of them are directly over the feet and the other two are over an 
>unsupported section of the bridge.

The incisions would not have that effect and the flexibility (as 
opposed to the rockability) of the bridge is not an issue.  Acoustic 
impedance is one thing; propagation of sound and acoustic radiation 
are another.  The proper regulation of the former creates the 
conditions for the efficient accomplishment of the latter.  Consider 
the etymology and the derivation of the word 'impedance'.

I have very little understanding of the guitar, the violin or the 
hurdy-gurdy but the physical and acoustic laws by which audible sound 
is produced from all stringed instruments is identical.  I suggest 
you have a look at

<<http://members.aol.com/jmluthier/>
<http://members.aol.com/jmluthier/sound.html>

And for general definitions, I refer you again to:

<http://www.sfu.ca/sonic-studio/handbook/>

JD