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Circular Membrane - Fixed


A circular membrane with zero thickness, fixed at its edged like a drum head.

(make-object 'circ-membrane ... )

Syntax and Default Values

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

(make-object 'circ-membrane
             (modes 80)
             (radius .5)
             (tension 1000)
             (surface-density 0.25)
             (freq-loss 1) 
             (const-loss 1))


The arguments for the physical parameters can be either numerical values or Modalys controllers (either dynamic or constant). If a given parameter is not supplied when using the Lisp syntax, the default parameter value will be used.

  • modes: number of modes.
  • radius: in meters.
  • tension: in Newtons.
  • surface-density: surface density in kilograms. NB: was named "mass" in older versions of Modalys.
  • freq-loss, const-loss: loss coefficients. See General object information.


A 'circ-membrane can be accessed only in its z-direction ('normal) from any point on its surface.

(make-access my-membrane my-2D-controller 'normal)
The first dimension of my-2D-controller is a number between zero and one which describes the distance from the center of the membrane to the edge (zero is at the center and 1 is at the edge). The second dimension describes the angle (in degrees) of the radius in question. If there is only one access, then, this dimension is of no importance and can be left at zero. If the membrane has several accesses, the angle is used to describe the relationship between them.

(make-access1 my-membrane (const 0.25 0) 'normal)
(make-access2 my-membrane (const 0.75 90) 'normal)



A circ-membrane can be tuned to a specific pitch, using the (set-pitch ...) function, by adjusting one of the following physical parameters:

  • 'radius
  • 'tension
  • 'mass

For example:

(setq my-membrane (make-object 'circ-membrane))
(set-pitch my-membrane 'radius 55)

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