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On Sat, 5 Jan 2002 10:39:39
John Delacour wrote:
>> 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.
I looked at your reference John. By the way, who is Mr. Parr?
I don't see anything in there that
contradicts what I said about the bridge motion. It does say something
about the time of travel of the vibrations in the bridge and vibrations
'circling around the incision' which seems to be at odds with
what I see in some of my references. Here are a couple:
http://hyperphysics.phy-astr.gsu.edu/hbase/music/violin.html#c5
An excerpt therefrom:
The action of the violin bridge is essential to the tone of the instrument. It's shape
and function have been developed over centuries. Underneath the treble side of
the bridge (where the E string rests) is the sound post which extends from the front
to the back plate of the instrument. Since this side of the bridge rests on this post,
it is essentially fixed and acts as a pivot for the rocking motion of the remainder of
the bridge. It does however, couple the sound energy from the top plate to the
back plate of the instrument.
Underneath the bass side of the bridge (where the G string rests), a long, thin
wooden strip called the bass bar is attached, almost parallel to the strings. This
bass foot of the bridge is more free to move, and its motion is the point of transfer
of energy from the strings to the top plate of the instrument. The extended bass
bar helps it to transfer the energy to a larger area of the top plate. As can be seen
from the diagram, the amplitude of motion is larger for the bass strings. This is
desirable for balance of loudness, since the sensitivity of the ear drops off a bit
toward the lower frequencies of the instrument.
I'll try to attach a GIF which I downloaded from this page, but I don't know
if it will come through. You may notice that the reference for the illustration
of bridge rocking and its explanation are from
Benade, A H Fundamentals of Musical Acoustics. Oxford University Press. 1976.
Another reference of interest:
http://www-ccrma.stanford.edu/courses/150/strings.html
And another quote:
The bridge transforms the motion of the vibrating string into a driving force on the top plate of the instrument.
The violin bridge typically has strong resonances around 3000 and 6000 Hz.
The bridge must move a small amount in order to transfer energy from the string to the body. For most musical instruments, however, the rate of energy transfer
from the string to the bridge and soundboard is quite small (energy decay in the string is most affected by air viscosity and internal string damping).
And another: http://www.speech.kth.se/qpsr/tmh/96-4-009-013.pdf. This shows
a diagram illustrating the motion which I mentioned. It also goes more into the
behavior of the violin, which shows that it is obviously much more complicated
than the simplistic explanation which I offered.
And another: http://members.aol.com/jmluthier/physics.html
And a quote:
Everyone knows that the soundpost is of great importance to the performance of the violin. I can add little except to say that I believe fit is usually as important or more so than
position. Often times, tinkering with the soundpost results in an improved sound simply because the post winds up being in the place where it fits the best. Very often, the top
has a depression or even a well-demarked dent where the post fits well. If a change of position of the post seems to give a better result, one should check for fit at that spot. If
the fit is not perfect, perhaps it will be a good idea to fit a post properly at this "sweet spot." Some practical advice to players who like to tinker: it is very easy to scar up and
shred the interior surface of the top by constant tapping around of the soundpost. Many violins have soundpost patches not for the repair of cracks, but to replace this shredded
wood.
The upper end of the post acts like a fulcrum upon which the top may rock. In the directon with the strings, the level arm distance from the post to the bridge foot can be
adjusted to determine the coupling of the right bridge foot to the top for higher frequencies. The cross-wise distance can be adjusted to change the lever arm from the fulcrum to
the bassbar/left bridge foot for lower frequencies. It has two degrees of freedom and allows for a fair amount of flexibility in adjustment. If the bottom end of the post needs
more or less support, it can be fitted to contact the back closer to or further from the rib. (see article on the "Back")
I don't know who this fellow is or what his background or credentials are, so you
can take it for what it's worth. I notice you're referencing him below to supposedly
counter my post.
>
>> 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.
Is this a serious discussion John. I was beginning to think it was a joke.
Sorry if my choice of words offends you. Sure and positively and words
like them tend to preclude an openminded evaluation of what others have
to say.
>I suggest
>you have a look at
>
><<http://members.aol.com/jmluthier/>
><http://members.aol.com/jmluthier/sound.html>
I did and once again I don't see anything that contradicts what I had to say
in my original post.
>
>And for general definitions, I refer you again to:
>
><http://www.sfu.ca/sonic-studio/handbook/>
>
>JD
>
Thanks, I'll have a look. I tend to be rather fast and loose with my terminology
so I hope this will help.
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