Article about bridge agraffes - function, types

[Ron Overs]

Ron N,

Your description of the boundary conditions around the temination 
points of the bridge agraffe appear to be very much on the money - 
nicely put. The three bp bridge agraffe will likely tend to reduce 
the bleed through effect compared to that of the 2bp agraffe.

A noisy back-scale with lots of energy bleed through from the 
speaking length might well  be accommodated by tuning the back scale 
segments. But in the case of the 2bp agraffes it might be nearly 
impossible to quell them when the damper calls for silence.

Ron O.

At 12:42 PM -0600 20/11/06, Ron Nossaman wrote:
>
>Hi Calin,
>I see it somewhat differently. The wood acts as a damper, yes, but 
>not for high frequencies, but rather for bleed through. The short 
>segments within a bridge agraffe are too short to sound audibly. 
>They are, however, long enough to transmit string motion, via 
>rocking on the bearing points, through to the back scale. This 
>doesn't happen in a conventionally pinned bridge, so with bridge 
>agraffes, you get a direct relationship between the string played, 
>and the back scale of that note. This is the way front duplexes 
>work, only it's on a moving bridge in this case instead of a more 
>solid plate, and the deflection angles are typically shallower in 
>the bridge agraffe, increasing the effect. It isn't a problem in the 
>lower portions of the scale because the back scale is typically 
>braided off down there already to prevent noise being generated by 
>the long back scales. I would bet that braiding off the back scale 
>would immediately kill that objectionable "agraffe" noise. But then 
>you wouldn't get the sound from the open back scale of a 
>conventionally pinned bridge, hence the rubber or felt dampers in 
>the agraffes. They kill the bleed through noises without killing the 
>typical and "normal" open back scale noise.
>
>My take,
>Ron N


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