Jet Object

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

The parameters for this object are a little different from regular objects:

• pressure: pressure controller for the jet.
• air-density: medium density of sound radiation in the propagating medium (kg/m^3).
• air-speed / celerity: swiftness/speed of the sound in the propagating medium (m/s).
• length: length of the flue for the jet formation
• width: width of the flue
• height: height of the flue
• flue-labium-distance: distance from the end of the flue to the labium
• labium-position: position of the labium with respect to the flue
• mouth-surface: this is set to 8e-5 by default and does not need to be changed

To simulate propagation in air (room temperature at sea level), you should use an air density value of 1.2 kg/m^3 (this parameter is sometimes called rho), and the speed of sound in air, 340 m/s, for air-speed (celerity can be used instead of air-speed for this parameter). The final mouth-surface controller has been documented for completeness but does not need to be provided.

The jet object is a special object in Modalys because it implements a nonlinear waveguide model, researched and created by Marc Pierre Verge for his doctoral thesis, instead of the usual modal description model. Consequently it is used is a slightly special way in the Modalys environment.

The fipple is the the mouthpiece of a whistle, recorder or other simple flute that generates a jet for sound production. The flue, sometimes also called a duct or “windway,” focuses a jet of air onto the sharp labium - also known as a blade or “windcutter.” The labium itself causes this jet to break into a vortex or whirlpool of air which oscillates back and forth across the labium. The image, above, shows the anatomy of a fipple, with several of its components that relate to this model clearly labeled.

The jet is a special object in that it is generally used directly by the 'labium connection, without an access.

In theory you can create accesses at three places on the jet object:

• 'foot
• 'flue-exit
• 'labium

However, for the moment we suggest just using the jet with the 'labium connection, as shown in the simple example script, below:

There are no specific options for this object, other than its parameters.