Glossary - edwardkort/WWIDesigner GitHub Wiki

Instrument Terms

Airstream Height (Flutes) - The thickness of the stream of air from the player's lips. This is almost impossible to measure; we suggest an estimate of 1.5 mm.

Airstream Length (Flutes) - The distance from the player's lips to the far edge of the embouchure hole. Variable, and almost impossible to measure precisely, this is one of the parameters that the flute calibrator adjusts to match predicted tuning to measured tuning.

Alpha (Reeds) - A parameter used in calibrating reed instruments, measured in milliseconds. This is one of the parameters the reed calibrator adjusts to match predicted tuning to measured tuning.

Beta Factor (Whistles, Flutes, Reeds) - A unitless (dimensionless) parameter used in modelling the instrument's loop gain, the "jet spatial amplification coefficient" in the work of Patricio de la Cuadra, and Roman Auvray (Bibliography). For most instruments, 0.4 is a useful starting point for beta; this is one of the parameters that the calibrators adjust to match predicted tuning to measured tuning. For whistles and flutes, the point where the loop gain drops below 1 determines the predicted minimum frequency for a note. Through its effect on loop gain, the beta factor affects the predicted minimum frequencies, and not the predicted maximum frequencies.

Bore Point - Any location along the interior of the instrument bore where the inside bore diameter has been measured or where the taper of the bore might change. WIDesigner assumes a uniform taper between bore points; the inside bore diameter changes in a straight line from one bore point to the next.

Bore Point Diameter - The inside diameter of the bore at the specified bore point.

Crow Frequency (Reeds) - The frequency of sound the bare reed and staple makes when you remove it from the instrument and blow or suck air through it. WIDesigner does not yet use this value.

Embouchure Hole Height (Flutes) - The thickness of the flute body at the embouchure hole, from the inside of the tube to the outside.

Embouchure Hole Length (Flutes) - The distance across the outside of the embouchure hole along the direction of the bore.

Embouchure Hole Width (Flutes) - The distance across the outside of the embouchure hole across (perpendicular to) the direction of the bore.

Fipple Factor (NAFs) - A unitless (dimensionless) parameter used in calibrating the instrument. This is the parameter that the NAF fipple factor calibrator adjusts to match predicted tuning to measured tuning.

Flue Depth (NAFs) - The thickness of the NAF body at the window or true sound hole, from the inside of the tube to the outside.

Hole Height - The thickness of the instrument body at the hole, from the inside of the tube to the outside, including the height of any flange around the outside of the hole.

Mouthpiece Position - For whistles, the position of the sound blade or splitting edge at the lower end of the window or true sound hole. For transverse flutes, the centre of the embouchure hole. For reeds, generally the bottom end of the staple, also used as the position of the top bore point.

Position (Holes, Bore points, Mouthpiece) - Distance along the bore of the instrument from a reference point in the direction toward the far end of the instrument and away from the mouthpiece. The reference point can be whatever point you find convenient to measure from. Points that are above the reference will have negative values for their position. The unit of measurement is selected on the WIDesigner Options dialogue.

Splitting Edge Position (NAFs) - The position of the sound blade or splitting edge at the lower end of the window or true sound hole.

Termination Flange Diameter - Total diameter of the outside of the very bottom of the bore.

TSH (NAFs) - True sound hole.

TSH Length (NAFs) - The distance between the output of the windway and the sound blade or splitting edge.

TSH Width (NAFs) - The distance across the window or true sound hole, side-to-side.

Window Height (Whistles) - The thickness of the whistle body at the window, from the inside of the tube to the outside, plus the height of any "ears" around the window. This distance can be difficult to define and measure precisely, often varying around the perimeter of the window; this is one of the parameters that the whistle calibrator adjusts to match predicted tuning to measured tuning.

Window Length (Whistles) - The distance between the output of the windway and the sound blade or splitting edge.

Window Width (Whistles) - The distance across the window, side-to-side.

Windway Length (Whistles) - The length of the windway, from the end you blow in, to the window. WIDesigner does not yet use this dimension.

Tuning and Acoustics Terms

Cents - A measure of the frequency difference of two musical sounds, one one-hundredth (0.01) of a semitone. For frequencies f1 and f2, the difference in cents is 1200 * log2(f1/f2). A semitone is 100 cents, half a semitone is 50 cents. Differences less than 5 cents are generally considered inaudible.

Fingering - The pattern of open and closed toneholes used to sound a particular note. With overblowing, the same fingering can produce different notes, and some instruments have more than one fingering for some notes. WIDesigner can support any arrangement of open and closed toneholes.

Frequency - The number of cycles the sound wave makes in one second, measured in cycles per second, or Hertz. For example, in the western concert pitch standard, the note A4, just above middle C on the piano, has a frequency of 440 Hertz. Frequency doubles every octave going up, and divides in half every octave going down.

Impedance - A measure of the response of a resonator (like an instrument bore) to sound at a specific frequency, denoted with the letter Z. WIDesigner makes extensive impedance calculations to predict playing frequencies. See https://newt.phys.unsw.edu.au/jw/z.html for a detailed explanation. (For convenience with reed instruments, WIDesigner calculates the reciprocal of impedance, called admittance.) Impedance has two parts: reactance, denoted as X, and resistance, denoted as R. WIDesigner often displays the ratio X/R--although X and R can each get very large, the ratio is more tractable for display.

Software Terms

XML - Short for eXtended Markup Language, a form of structured text useful for recording data structures. XML files are easily read and written by computer programs; they are also human-readable and -writable with the help of a text editor. WIDesigner uses XML files to record data about instruments, about tunings, and about optimizer constraints.