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Cello Bridge

Description

A basic cello bridge model.

Syntax and Default Values

A 'cello-bridge can be created using the following Lisp syntax (the default values are shown for each of the physical parameters):

(make-object 'cello-bridge
             (m1-mass .0046)
             (m2-mass .0059)
             (m12-mass .0024)
             (d-distance .032)
             (d20-distance .011)
             (h1-distance .052)
             (a-distance .035)
             (i20-distance .026)
             (d2-stiffness 716.8)
             (s1-stiffness 360000)
             (freq-loss 10)
             (const-loss 10))

Parameters

All physical parameters can be numerical values or controllers.

  • m1-mass: central mass of the bridge in kg
  • m2-mass: masses at the upper part of the bridge in kg
  • m12-mass: masses at the base/feet of the bridge in kg
  • d-distance: distance from the string to the central mass in meters
  • d20-distance: distance from the central mass to the upper mass in meters
  • h1-distance: distance from the central mass to the feet in meters
  • a-distance: distance from the center to the edge of the bridge (i.e. half the total bridge width) in meters
  • i20-distance: distance from the center to the upper masses on either side of the bridge in meters
  • d2-stiffness: stiffness of the central mass spring
  • s1-stiffness: stiffness from the central mass to the feet
  • freq-loss, const-loss: loss coefficients. See General object information.

Accesses

To access the feet of a cello bridge (to adhere it to an instrument body, or make an output on it, for example), the special access type 'base is used. -1 refers to the left foot, and 1 refers to the right. (A number in-between will specify an access somewhere in the middle.)

(make-access my-cello-bridge (const -1) 'base) ;;; left foot
(make-access my-cello-bridge (const 1) 'base) ;;; right foot
Note that these feet are vertically vibrating accesses. To attach strings (or plates, if you want), to the top part of the bridge, the access types 'top-vertical and 'top-horizontal are used.

(make-access my-cello-bridge (const distance) 'top-horizontal)
(make-access my-cello-bridge (const distance) 'top-vertical)
In the case of a bi-string, one would normally use two access (both 'trans0 and 'trans1) at a point on the string attached to the two access directions on the bridge. The value distance describes the distance (in meters) from the center of the bridge to the access. Note that the any value can be given for this variable; one could easily have a bridge which is twelve kilometers long (attached to a very large cello!).


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